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Here are several miscellaneous parameters.
Define this boolean macro to indicate whether or not your architecture has conditional branches that can span all of memory. It is used in conjunction with an optimization that partitions hot and cold basic blocks into separate sections of the executable. If this macro is set to false, gcc will convert any conditional branches that attempt to cross between sections into unconditional branches or indirect jumps.
Define this boolean macro to indicate whether or not your architecture has unconditional branches that can span all of memory. It is used in conjunction with an optimization that partitions hot and cold basic blocks into separate sections of the executable. If this macro is set to false, gcc will convert any unconditional branches that attempt to cross between sections into indirect jumps.
An alias for a machine mode name. This is the machine mode that elements of a jump-table should have.
Optional: return the preferred mode for an
addr_diff_vec
when the minimum and maximum offset are known. If you define this, it enables extra code in branch shortening to deal withaddr_diff_vec
. To make this work, you also have to defineINSN_ALIGN
and make the alignment foraddr_diff_vec
explicit. The body argument is provided so that the offset_unsigned and scale flags can be updated.
Define this macro to be a C expression to indicate when jump-tables should contain relative addresses. You need not define this macro if jump-tables never contain relative addresses, or jump-tables should contain relative addresses only when -fPIC or -fPIC is in effect.
This function return the smallest number of different values for which it is best to use a jump-table instead of a tree of conditional branches. The default is four for machines with a
casesi
instruction and five otherwise. This is best for most machines.
Define this macro to be a C expression to indicate whether C switch statements may be implemented by a sequence of bit tests. This is advantageous on processors that can efficiently implement left shift of 1 by the number of bits held in a register, but inappropriate on targets that would require a loop. By default, this macro returns
true
if the target defines anashlsi3
pattern, andfalse
otherwise.
Define this macro if operations between registers with integral mode smaller than a word are always performed on the entire register. Most RISC machines have this property and most CISC machines do not.
Define this macro to be a C expression indicating when insns that read memory in mem_mode, an integral mode narrower than a word, set the bits outside of mem_mode to be either the sign-extension or the zero-extension of the data read. Return
SIGN_EXTEND
for values of mem_mode for which the insn sign-extends,ZERO_EXTEND
for which it zero-extends, andUNKNOWN
for other modes.This macro is not called with mem_mode non-integral or with a width greater than or equal to
BITS_PER_WORD
, so you may return any value in this case. Do not define this macro if it would always returnUNKNOWN
. On machines where this macro is defined, you will normally define it as the constantSIGN_EXTEND
orZERO_EXTEND
.You may return a non-
UNKNOWN
value even if for some hard registers the sign extension is not performed, if for theREGNO_REG_CLASS
of these hard registersCANNOT_CHANGE_MODE_CLASS
returns nonzero when the from mode is mem_mode and the to mode is any integral mode larger than this but not larger thanword_mode
.You must return
UNKNOWN
if for some hard registers that allow this mode,CANNOT_CHANGE_MODE_CLASS
says that they cannot change toword_mode
, but that they can change to another integral mode that is larger then mem_mode but still smaller thanword_mode
.
Define this macro if loading short immediate values into registers sign extends.
Define this macro if the same instructions that convert a floating point number to a signed fixed point number also convert validly to an unsigned one.
When -ffast-math is in effect, GCC tries to optimize divisions by the same divisor, by turning them into multiplications by the reciprocal. This target hook specifies the minimum number of divisions that should be there for GCC to perform the optimization for a variable of mode mode. The default implementation returns 3 if the machine has an instruction for the division, and 2 if it does not.
The maximum number of bytes that a single instruction can move quickly between memory and registers or between two memory locations.
The maximum number of bytes that a single instruction can move quickly between memory and registers or between two memory locations. If this is undefined, the default is
MOVE_MAX
. Otherwise, it is the constant value that is the largest value thatMOVE_MAX
can have at run-time.
A C expression that is nonzero if on this machine the number of bits actually used for the count of a shift operation is equal to the number of bits needed to represent the size of the object being shifted. When this macro is nonzero, the compiler will assume that it is safe to omit a sign-extend, zero-extend, and certain bitwise `and' instructions that truncates the count of a shift operation. On machines that have instructions that act on bit-fields at variable positions, which may include `bit test' instructions, a nonzero
SHIFT_COUNT_TRUNCATED
also enables deletion of truncations of the values that serve as arguments to bit-field instructions.If both types of instructions truncate the count (for shifts) and position (for bit-field operations), or if no variable-position bit-field instructions exist, you should define this macro.
However, on some machines, such as the 80386 and the 680x0, truncation only applies to shift operations and not the (real or pretended) bit-field operations. Define
SHIFT_COUNT_TRUNCATED
to be zero on such machines. Instead, add patterns to the md file that include the implied truncation of the shift instructions.You need not define this macro if it would always have the value of zero.
This function describes how the standard shift patterns for mode deal with shifts by negative amounts or by more than the width of the mode. See shift patterns.
On many machines, the shift patterns will apply a mask m to the shift count, meaning that a fixed-width shift of x by y is equivalent to an arbitrary-width shift of x by y & m. If this is true for mode mode, the function should return m, otherwise it should return 0. A return value of 0 indicates that no particular behavior is guaranteed.
Note that, unlike
SHIFT_COUNT_TRUNCATED
, this function does not apply to general shift rtxes; it applies only to instructions that are generated by the named shift patterns.The default implementation of this function returns
GET_MODE_BITSIZE (
mode) - 1
ifSHIFT_COUNT_TRUNCATED
and 0 otherwise. This definition is always safe, but ifSHIFT_COUNT_TRUNCATED
is false, and some shift patterns nevertheless truncate the shift count, you may get better code by overriding it.
A C expression which is nonzero if on this machine it is safe to “convert” an integer of inprec bits to one of outprec bits (where outprec is smaller than inprec) by merely operating on it as if it had only outprec bits.
On many machines, this expression can be 1.
When
TRULY_NOOP_TRUNCATION
returns 1 for a pair of sizes for modes for whichMODES_TIEABLE_P
is 0, suboptimal code can result. If this is the case, makingTRULY_NOOP_TRUNCATION
return 0 in such cases may improve things.
The representation of an integral mode can be such that the values are always extended to a wider integral mode. Return
SIGN_EXTEND
if values of mode are represented in sign-extended form to rep_mode. ReturnUNKNOWN
otherwise. (Currently, none of the targets use zero-extended representation this way so unlikeLOAD_EXTEND_OP
,TARGET_MODE_REP_EXTENDED
is expected to return eitherSIGN_EXTEND
orUNKNOWN
. Also no target extends mode to rep_mode so that rep_mode is not the next widest integral mode and currently we take advantage of this fact.)Similarly to
LOAD_EXTEND_OP
you may return a non-UNKNOWN
value even if the extension is not performed on certain hard registers as long as for theREGNO_REG_CLASS
of these hard registersCANNOT_CHANGE_MODE_CLASS
returns nonzero.Note that
TARGET_MODE_REP_EXTENDED
andLOAD_EXTEND_OP
describe two related properties. If you defineTARGET_MODE_REP_EXTENDED (mode, word_mode)
you probably also want to defineLOAD_EXTEND_OP (mode)
to return the same type of extension.In order to enforce the representation of
mode
,TRULY_NOOP_TRUNCATION
should return false when truncating tomode
.
A C expression describing the value returned by a comparison operator with an integral mode and stored by a store-flag instruction (`cstoremode4') when the condition is true. This description must apply to all the `cstoremode4' patterns and all the comparison operators whose results have a
MODE_INT
mode.A value of 1 or −1 means that the instruction implementing the comparison operator returns exactly 1 or −1 when the comparison is true and 0 when the comparison is false. Otherwise, the value indicates which bits of the result are guaranteed to be 1 when the comparison is true. This value is interpreted in the mode of the comparison operation, which is given by the mode of the first operand in the `cstoremode4' pattern. Either the low bit or the sign bit of
STORE_FLAG_VALUE
be on. Presently, only those bits are used by the compiler.If
STORE_FLAG_VALUE
is neither 1 or −1, the compiler will generate code that depends only on the specified bits. It can also replace comparison operators with equivalent operations if they cause the required bits to be set, even if the remaining bits are undefined. For example, on a machine whose comparison operators return anSImode
value and whereSTORE_FLAG_VALUE
is defined as `0x80000000', saying that just the sign bit is relevant, the expression(ne:SI (and:SI x (const_int power-of-2)) (const_int 0))can be converted to
(ashift:SI x (const_int n))where n is the appropriate shift count to move the bit being tested into the sign bit.
There is no way to describe a machine that always sets the low-order bit for a true value, but does not guarantee the value of any other bits, but we do not know of any machine that has such an instruction. If you are trying to port GCC to such a machine, include an instruction to perform a logical-and of the result with 1 in the pattern for the comparison operators and let us know at [email protected].
Often, a machine will have multiple instructions that obtain a value from a comparison (or the condition codes). Here are rules to guide the choice of value for
STORE_FLAG_VALUE
, and hence the instructions to be used:
- Use the shortest sequence that yields a valid definition for
STORE_FLAG_VALUE
. It is more efficient for the compiler to “normalize” the value (convert it to, e.g., 1 or 0) than for the comparison operators to do so because there may be opportunities to combine the normalization with other operations.- For equal-length sequences, use a value of 1 or −1, with −1 being slightly preferred on machines with expensive jumps and 1 preferred on other machines.
- As a second choice, choose a value of `0x80000001' if instructions exist that set both the sign and low-order bits but do not define the others.
- Otherwise, use a value of `0x80000000'.
Many machines can produce both the value chosen for
STORE_FLAG_VALUE
and its negation in the same number of instructions. On those machines, you should also define a pattern for those cases, e.g., one matching(set A (neg:m (ne:m B C)))Some machines can also perform
and
orplus
operations on condition code values with less instructions than the corresponding `cstoremode4' insn followed byand
orplus
. On those machines, define the appropriate patterns. Use the namesincscc
anddecscc
, respectively, for the patterns which performplus
orminus
operations on condition code values. See rs6000.md for some examples. The GNU Superoptimizer can be used to find such instruction sequences on other machines.If this macro is not defined, the default value, 1, is used. You need not define
STORE_FLAG_VALUE
if the machine has no store-flag instructions, or if the value generated by these instructions is 1.
A C expression that gives a nonzero
REAL_VALUE_TYPE
value that is returned when comparison operators with floating-point results are true. Define this macro on machines that have comparison operations that return floating-point values. If there are no such operations, do not define this macro.
A C expression that gives a rtx representing the nonzero true element for vector comparisons. The returned rtx should be valid for the inner mode of mode which is guaranteed to be a vector mode. Define this macro on machines that have vector comparison operations that return a vector result. If there are no such operations, do not define this macro. Typically, this macro is defined as
const1_rtx
orconstm1_rtx
. This macro may returnNULL_RTX
to prevent the compiler optimizing such vector comparison operations for the given mode.
A C expression that indicates whether the architecture defines a value for
clz
orctz
with a zero operand. A result of0
indicates the value is undefined. If the value is defined for only the RTL expression, the macro should evaluate to1
; if the value applies also to the corresponding optab entry (which is normally the case if it expands directly into the corresponding RTL), then the macro should evaluate to2
. In the cases where the value is defined, value should be set to this value.If this macro is not defined, the value of
clz
orctz
at zero is assumed to be undefined.This macro must be defined if the target's expansion for
ffs
relies on a particular value to get correct results. Otherwise it is not necessary, though it may be used to optimize some corner cases, and to provide a default expansion for theffs
optab.Note that regardless of this macro the “definedness” of
clz
andctz
at zero do not extend to the builtin functions visible to the user. Thus one may be free to adjust the value at will to match the target expansion of these operations without fear of breaking the API.
An alias for the machine mode for pointers. On most machines, define this to be the integer mode corresponding to the width of a hardware pointer;
SImode
on 32-bit machine orDImode
on 64-bit machines. On some machines you must define this to be one of the partial integer modes, such asPSImode
.The width of
Pmode
must be at least as large as the value ofPOINTER_SIZE
. If it is not equal, you must define the macroPOINTERS_EXTEND_UNSIGNED
to specify how pointers are extended toPmode
.
An alias for the machine mode used for memory references to functions being called, in
call
RTL expressions. On most CISC machines, where an instruction can begin at any byte address, this should beQImode
. On most RISC machines, where all instructions have fixed size and alignment, this should be a mode with the same size and alignment as the machine instruction words - typicallySImode
orHImode
.
In normal operation, the preprocessor expands
__STDC__
to the constant 1, to signify that GCC conforms to ISO Standard C. On some hosts, like Solaris, the system compiler uses a different convention, where__STDC__
is normally 0, but is 1 if the user specifies strict conformance to the C Standard.Defining
STDC_0_IN_SYSTEM_HEADERS
makes GNU CPP follows the host convention when processing system header files, but when processing user files__STDC__
will always expand to 1.
Define this macro if the system header files support C++ as well as C. This macro inhibits the usual method of using system header files in C++, which is to pretend that the file's contents are enclosed in `extern "C" {...}'.
Define this macro if you want to implement any target-specific pragmas. If defined, it is a C expression which makes a series of calls to
c_register_pragma
orc_register_pragma_with_expansion
for each pragma. The macro may also do any setup required for the pragmas.The primary reason to define this macro is to provide compatibility with other compilers for the same target. In general, we discourage definition of target-specific pragmas for GCC.
If the pragma can be implemented by attributes then you should consider defining the target hook `TARGET_INSERT_ATTRIBUTES' as well.
Preprocessor macros that appear on pragma lines are not expanded. All `#pragma' directives that do not match any registered pragma are silently ignored, unless the user specifies -Wunknown-pragmas.
Each call to
c_register_pragma
orc_register_pragma_with_expansion
establishes one pragma. The callback routine will be called when the preprocessor encounters a pragma of the form#pragma [space] name ...space is the case-sensitive namespace of the pragma, or
NULL
to put the pragma in the global namespace. The callback routine receives pfile as its first argument, which can be passed on to cpplib's functions if necessary. You can lex tokens after the name by callingpragma_lex
. Tokens that are not read by the callback will be silently ignored. The end of the line is indicated by a token of typeCPP_EOF
. Macro expansion occurs on the arguments of pragmas registered withc_register_pragma_with_expansion
but not on the arguments of pragmas registered withc_register_pragma
.Note that the use of
pragma_lex
is specific to the C and C++ compilers. It will not work in the Java or Fortran compilers, or any other language compilers for that matter. Thus ifpragma_lex
is going to be called from target-specific code, it must only be done so when building the C and C++ compilers. This can be done by defining the variablesc_target_objs
andcxx_target_objs
in the target entry in the config.gcc file. These variables should name the target-specific, language-specific object file which contains the code that usespragma_lex
. Note it will also be necessary to add a rule to the makefile fragment pointed to bytmake_file
that shows how to build this object file.
Define this macro if macros should be expanded in the arguments of `#pragma pack'.
True if
#pragma extern_prefix
is to be supported.
If your target requires a structure packing default other than 0 (meaning the machine default), define this macro to the necessary value (in bytes). This must be a value that would also be valid to use with `#pragma pack()' (that is, a small power of two).
Define this macro to control use of the character `$' in identifier names for the C family of languages. 0 means `$' is not allowed by default; 1 means it is allowed. 1 is the default; there is no need to define this macro in that case.
Define this macro if the assembler does not accept the character `$' in label names. By default constructors and destructors in G++ have `$' in the identifiers. If this macro is defined, `.' is used instead.
Define this macro if the assembler does not accept the character `.' in label names. By default constructors and destructors in G++ have names that use `.'. If this macro is defined, these names are rewritten to avoid `.'.
Define this macro as a C expression that is nonzero if it is safe for the delay slot scheduler to place instructions in the delay slot of insn, even if they appear to use a resource set or clobbered in insn. insn is always a
jump_insn
or aninsn
; GCC knows that everycall_insn
has this behavior. On machines where someinsn
orjump_insn
is really a function call and hence has this behavior, you should define this macro.You need not define this macro if it would always return zero.
Define this macro as a C expression that is nonzero if it is safe for the delay slot scheduler to place instructions in the delay slot of insn, even if they appear to set or clobber a resource referenced in insn. insn is always a
jump_insn
or aninsn
. On machines where someinsn
orjump_insn
is really a function call and its operands are registers whose use is actually in the subroutine it calls, you should define this macro. Doing so allows the delay slot scheduler to move instructions which copy arguments into the argument registers into the delay slot of insn.You need not define this macro if it would always return zero.
Define this macro as a C expression that is nonzero if, in some cases, global symbols from one translation unit may not be bound to undefined symbols in another translation unit without user intervention. For instance, under Microsoft Windows symbols must be explicitly imported from shared libraries (DLLs).
You need not define this macro if it would always evaluate to zero.
This target hook should add to clobbers
STRING_CST
trees for any hard regs the port wishes to automatically clobber for an asm. It should return the result of the lasttree_cons
used to add a clobber. The outputs, inputs and clobber lists are the corresponding parameters to the asm and may be inspected to avoid clobbering a register that is an input or output of the asm. You can usetree_overlaps_hard_reg_set
, declared in tree.h, to test for overlap with regards to asm-declared registers.
Define this macro as a C string constant for the linker argument to link in the system math library, minus the initial `"-l"', or `""' if the target does not have a separate math library.
You need only define this macro if the default of `"m"' is wrong.
Define this macro as a C string constant for the environment variable that specifies where the linker should look for libraries.
You need only define this macro if the default of `"LIBRARY_PATH"' is wrong.
Define this macro if the target supports the following POSIX file functions, access, mkdir and file locking with fcntl / F_SETLKW. Defining
TARGET_POSIX_IO
will enable the test coverage code to use file locking when exiting a program, which avoids race conditions if the program has forked. It will also create directories at run-time for cross-profiling.
A C expression for the maximum number of instructions to execute via conditional execution instructions instead of a branch. A value of
BRANCH_COST
+1 is the default if the machine does not use cc0, and 1 if it does use cc0.
Used if the target needs to perform machine-dependent modifications on the conditionals used for turning basic blocks into conditionally executed code. ce_info points to a data structure,
struct ce_if_block
, which contains information about the currently processed blocks. true_expr and false_expr are the tests that are used for converting the then-block and the else-block, respectively. Set either true_expr or false_expr to a null pointer if the tests cannot be converted.
Like
IFCVT_MODIFY_TESTS
, but used when converting more complicated if-statements into conditions combined byand
andor
operations. bb contains the basic block that contains the test that is currently being processed and about to be turned into a condition.
A C expression to modify the PATTERN of an INSN that is to be converted to conditional execution format. ce_info points to a data structure,
struct ce_if_block
, which contains information about the currently processed blocks.
A C expression to perform any final machine dependent modifications in converting code to conditional execution. The involved basic blocks can be found in the
struct ce_if_block
structure that is pointed to by ce_info.
A C expression to cancel any machine dependent modifications in converting code to conditional execution. The involved basic blocks can be found in the
struct ce_if_block
structure that is pointed to by ce_info.
A C expression to initialize any extra fields in a
struct ce_if_block
structure, which are defined by theIFCVT_EXTRA_FIELDS
macro.
If defined, it should expand to a set of field declarations that will be added to the
struct ce_if_block
structure. These should be initialized by theIFCVT_INIT_EXTRA_FIELDS
macro.
If non-null, this hook performs a target-specific pass over the instruction stream. The compiler will run it at all optimization levels, just before the point at which it normally does delayed-branch scheduling.
The exact purpose of the hook varies from target to target. Some use it to do transformations that are necessary for correctness, such as laying out in-function constant pools or avoiding hardware hazards. Others use it as an opportunity to do some machine-dependent optimizations.
You need not implement the hook if it has nothing to do. The default definition is null.
Define this hook if you have any machine-specific built-in functions that need to be defined. It should be a function that performs the necessary setup.
Machine specific built-in functions can be useful to expand special machine instructions that would otherwise not normally be generated because they have no equivalent in the source language (for example, SIMD vector instructions or prefetch instructions).
To create a built-in function, call the function
lang_hooks.builtin_function
which is defined by the language front end. You can use any type nodes set up bybuild_common_tree_nodes
andbuild_common_tree_nodes_2
; only language front ends that use those two functions will call `TARGET_INIT_BUILTINS'.
Define this hook if you have any machine-specific built-in functions that need to be defined. It should be a function that returns the builtin function declaration for the builtin function code code. If there is no such builtin and it cannot be initialized at this time if initialize_p is true the function should return
NULL_TREE
. If code is out of range the function should returnerror_mark_node
.
Expand a call to a machine specific built-in function that was set up by `TARGET_INIT_BUILTINS'. exp is the expression for the function call; the result should go to target if that is convenient, and have mode mode if that is convenient. subtarget may be used as the target for computing one of exp's operands. ignore is nonzero if the value is to be ignored. This function should return the result of the call to the built-in function.
Select a replacement for a machine specific built-in function that was set up by `TARGET_INIT_BUILTINS'. This is done before regular type checking, and so allows the target to implement a crude form of function overloading. fndecl is the declaration of the built-in function. arglist is the list of arguments passed to the built-in function. The result is a complete expression that implements the operation, usually another
CALL_EXPR
. arglist really has type `VEC(tree,gc)*'
Fold a call to a machine specific built-in function that was set up by `TARGET_INIT_BUILTINS'. fndecl is the declaration of the built-in function. n_args is the number of arguments passed to the function; the arguments themselves are pointed to by argp. The result is another tree containing a simplified expression for the call's result. If ignore is true the value will be ignored.
Take an instruction in insn and return NULL if it is valid within a low-overhead loop, otherwise return a string explaining why doloop could not be applied.
Many targets use special registers for low-overhead looping. For any instruction that clobbers these this function should return a string indicating the reason why the doloop could not be applied. By default, the RTL loop optimizer does not use a present doloop pattern for loops containing function calls or branch on table instructions.
Take a branch insn in branch1 and another in branch2. Return true if redirecting branch1 to the destination of branch2 is possible.
On some targets, branches may have a limited range. Optimizing the filling of delay slots can result in branches being redirected, and this may in turn cause a branch offset to overflow.
This target hook returns
true
if x is considered to be commutative. Usually, this is just COMMUTATIVE_P (x), but the HP PA doesn't consider PLUS to be commutative inside a MEM. outer_code is the rtx code of the enclosing rtl, if known, otherwise it is UNKNOWN.
When the initial value of a hard register has been copied in a pseudo register, it is often not necessary to actually allocate another register to this pseudo register, because the original hard register or a stack slot it has been saved into can be used.
TARGET_ALLOCATE_INITIAL_VALUE
is called at the start of register allocation once for each hard register that had its initial value copied by usingget_func_hard_reg_initial_val
orget_hard_reg_initial_val
. Possible values areNULL_RTX
, if you don't want to do any special allocation, aREG
rtx—that would typically be the hard register itself, if it is known not to be clobbered—or aMEM
. If you are returning aMEM
, this is only a hint for the allocator; it might decide to use another register anyways. You may usecurrent_function_leaf_function
in the hook, functions that useREG_N_SETS
, to determine if the hard register in question will not be clobbered. The default value of this hook isNULL
, which disables any special allocation.
This target hook returns nonzero if x, an
unspec
orunspec_volatile
operation, might cause a trap. Targets can use this hook to enhance precision of analysis forunspec
andunspec_volatile
operations. You may callmay_trap_p_1
to analyze inner elements of x in which case flags should be passed along.
The compiler invokes this hook whenever it changes its current function context (
cfun
). You can define this function if the back end needs to perform any initialization or reset actions on a per-function basis. For example, it may be used to implement function attributes that affect register usage or code generation patterns. The argument decl is the declaration for the new function context, and may be null to indicate that the compiler has left a function context and is returning to processing at the top level. The default hook function does nothing.GCC sets
cfun
to a dummy function context during initialization of some parts of the back end. The hook function is not invoked in this situation; you need not worry about the hook being invoked recursively, or when the back end is in a partially-initialized state.cfun
might beNULL
to indicate processing at top level, outside of any function scope.
Define this macro to be a C string representing the suffix for object files on your target machine. If you do not define this macro, GCC will use `.o' as the suffix for object files.
Define this macro to be a C string representing the suffix to be automatically added to executable files on your target machine. If you do not define this macro, GCC will use the null string as the suffix for executable files.
If defined,
collect2
will scan the individual object files specified on its command line and create an export list for the linker. Define this macro for systems like AIX, where the linker discards object files that are not referenced frommain
and uses export lists.
Define this macro to a C expression representing a variant of the method call mdecl, if Java Native Interface (JNI) methods must be invoked differently from other methods on your target. For example, on 32-bit Microsoft Windows, JNI methods must be invoked using the
stdcall
calling convention and this macro is then defined as this expression:build_type_attribute_variant (mdecl, build_tree_list (get_identifier ("stdcall"), NULL))
This target hook returns
true
past the point in which new jump instructions could be created. On machines that require a register for every jump such as the SHmedia ISA of SH5, this point would typically be reload, so this target hook should be defined to a function such as:static bool cannot_modify_jumps_past_reload_p () { return (reload_completed || reload_in_progress); }
This target hook returns a register class for which branch target register optimizations should be applied. All registers in this class should be usable interchangeably. After reload, registers in this class will be re-allocated and loads will be hoisted out of loops and be subjected to inter-block scheduling.
Branch target register optimization will by default exclude callee-saved registers that are not already live during the current function; if this target hook returns true, they will be included. The target code must than make sure that all target registers in the class returned by `TARGET_BRANCH_TARGET_REGISTER_CLASS' that might need saving are saved. after_prologue_epilogue_gen indicates if prologues and epilogues have already been generated. Note, even if you only return true when after_prologue_epilogue_gen is false, you still are likely to have to make special provisions in
INITIAL_ELIMINATION_OFFSET
to reserve space for caller-saved target registers.
This target hook returns true if the target supports conditional execution. This target hook is required only when the target has several different modes and they have different conditional execution capability, such as ARM.
This target hook returns a new value for the number of times loop should be unrolled. The parameter nunroll is the number of times the loop is to be unrolled. The parameter loop is a pointer to the loop, which is going to be checked for unrolling. This target hook is required only when the target has special constraints like maximum number of memory accesses.
If defined, this macro is interpreted as a signed integer C expression that specifies the maximum number of floating point multiplications that should be emitted when expanding exponentiation by an integer constant inline. When this value is defined, exponentiation requiring more than this number of multiplications is implemented by calling the system library's
pow
,powf
orpowl
routines. The default value places no upper bound on the multiplication count.
This target hook should register any extra include files for the target. The parameter stdinc indicates if normal include files are present. The parameter sysroot is the system root directory. The parameter iprefix is the prefix for the gcc directory.
This target hook should register any extra include files for the target before any standard headers. The parameter stdinc indicates if normal include files are present. The parameter sysroot is the system root directory. The parameter iprefix is the prefix for the gcc directory.
This target hook should register special include paths for the target. The parameter path is the include to register. On Darwin systems, this is used for Framework includes, which have semantics that are different from -I.
This target macro returns
true
if it is safe to use a local alias for a virtual function fndecl when constructing thunks,false
otherwise. By default, the macro returnstrue
for all functions, if a target supports aliases (i.e. definesASM_OUTPUT_DEF
),false
otherwise,
If defined, this macro is the name of a global variable containing target-specific format checking information for the -Wformat option. The default is to have no target-specific format checks.
If defined, this macro is the number of entries in
TARGET_FORMAT_TYPES
.
If defined, this macro is the name of a global variable containing target-specific format overrides for the -Wformat option. The default is to have no target-specific format overrides. If defined,
TARGET_FORMAT_TYPES
must be defined, too.
If defined, this macro specifies the number of entries in
TARGET_OVERRIDES_FORMAT_ATTRIBUTES
.
If defined, this macro specifies the optional initialization routine for target specific customizations of the system printf and scanf formatter settings.
If set to
true
, means that the target's memory model does not guarantee that loads which do not depend on one another will access main memory in the order of the instruction stream; if ordering is important, an explicit memory barrier must be used. This is true of many recent processors which implement a policy of “relaxed,” “weak,” or “release” memory consistency, such as Alpha, PowerPC, and ia64. The default isfalse
.
If defined, this macro returns the diagnostic message when it is illegal to pass argument val to function funcdecl with prototype typelist.
If defined, this macro returns the diagnostic message when it is invalid to convert from fromtype to totype, or
NULL
if validity should be determined by the front end.
If defined, this macro returns the diagnostic message when it is invalid to apply operation op (where unary plus is denoted by
CONVERT_EXPR
) to an operand of type type, orNULL
if validity should be determined by the front end.
If defined, this macro returns the diagnostic message when it is invalid to apply operation op to operands of types type1 and type2, or
NULL
if validity should be determined by the front end.
If defined, this macro returns the diagnostic message when it is invalid for functions to include parameters of type type, or
NULL
if validity should be determined by the front end. This is currently used only by the C and C++ front ends.
If defined, this macro returns the diagnostic message when it is invalid for functions to have return type type, or
NULL
if validity should be determined by the front end. This is currently used only by the C and C++ front ends.
If defined, this target hook returns the type to which values of type should be promoted when they appear in expressions, analogous to the integer promotions, or
NULL_TREE
to use the front end's normal promotion rules. This hook is useful when there are target-specific types with special promotion rules. This is currently used only by the C and C++ front ends.
If defined, this hook returns the result of converting expr to type. It should return the converted expression, or
NULL_TREE
to apply the front end's normal conversion rules. This hook is useful when there are target-specific types with special conversion rules. This is currently used only by the C and C++ front ends.
This macro determines whether to use the JCR section to register Java classes. By default, TARGET_USE_JCR_SECTION is defined to 1 if both SUPPORTS_WEAK and TARGET_HAVE_NAMED_SECTIONS are true, else 0.
This macro determines the size of the objective C jump buffer for the NeXT runtime. By default, OBJC_JBLEN is defined to an innocuous value.
Define this macro if any target-specific attributes need to be attached to the functions in libgcc that provide low-level support for call stack unwinding. It is used in declarations in unwind-generic.h and the associated definitions of those functions.
Define this macro to update the current function stack boundary if necessary.
This hook should return an rtx for Dynamic Realign Argument Pointer (DRAP) if a different argument pointer register is needed to access the function's argument list due to stack realignment. Return
NULL
if no DRAP is needed.
When optimization is disabled, this hook indicates whether or not arguments should be allocated to stack slots. Normally, GCC allocates stacks slots for arguments when not optimizing in order to make debugging easier. However, when a function is declared with
__attribute__((naked))
, there is no stack frame, and the compiler cannot safely move arguments from the registers in which they are passed to the stack. Therefore, this hook should return true in general, but false for naked functions. The default implementation always returns true.
On some architectures it can take multiple instructions to synthesize a constant. If there is another constant already in a register that is close enough in value then it is preferable that the new constant is computed from this register using immediate addition or subtraction. We accomplish this through CSE. Besides the value of the constant we also add a lower and an upper constant anchor to the available expressions. These are then queried when encountering new constants. The anchors are computed by rounding the constant up and down to a multiple of the value of
TARGET_CONST_ANCHOR
.TARGET_CONST_ANCHOR
should be the maximum positive value accepted by immediate-add plus one. We currently assume that the value ofTARGET_CONST_ANCHOR
is a power of 2. For example, on MIPS, where add-immediate takes a 16-bit signed value,TARGET_CONST_ANCHOR
is set to `0x8000'. The default value is zero, which disables this optimization.