/* Definitions of x86 tunable features.
Copyright (C) 2013-2015 Free Software Foundation, Inc.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
/* Tuning for a given CPU XXXX consists of:
- adding new CPU into:
- adding PROCESSOR_XXX to processor_type (in i386.h)
- possibly adding XXX into CPU attribute in i386.md
- adding XXX to processor_alias_table (in i386.c)
- introducing ix86_XXX_cost in i386.c
- Stringop generation table can be build based on test_stringop
- script (once rest of tuning is complete)
- designing a scheduler model in
- XXXX.md file
- Updating ix86_issue_rate and ix86_adjust_cost in i386.md
- possibly updating ia32_multipass_dfa_lookahead, ix86_sched_reorder
and ix86_sched_init_global if those tricks are needed.
- Tunning the flags bellow. Those are split into sections and each
section is very roughly ordered by importance. */
/*****************************************************************************/
/* Scheduling flags. */
/*****************************************************************************/
/* X86_TUNE_SCHEDULE: Enable scheduling. */
DEF_TUNE (X86_TUNE_SCHEDULE, "schedule",
m_PENT | m_PPRO | m_CORE_ALL | m_BONNELL | m_SILVERMONT | m_INTEL
| m_KNL | m_K6_GEODE | m_AMD_MULTIPLE | m_GENERIC)
/* X86_TUNE_PARTIAL_REG_DEPENDENCY: Enable more register renaming
on modern chips. Preffer stores affecting whole integer register
over partial stores. For example preffer MOVZBL or MOVQ to load 8bit
value over movb. */
DEF_TUNE (X86_TUNE_PARTIAL_REG_DEPENDENCY, "partial_reg_dependency",
m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT | m_INTEL
| m_KNL | m_AMD_MULTIPLE | m_GENERIC)
/* X86_TUNE_SSE_PARTIAL_REG_DEPENDENCY: This knob promotes all store
destinations to be 128bit to allow register renaming on 128bit SSE units,
but usually results in one extra microop on 64bit SSE units.
Experimental results shows that disabling this option on P4 brings over 20%
SPECfp regression, while enabling it on K8 brings roughly 2.4% regression
that can be partly masked by careful scheduling of moves. */
DEF_TUNE (X86_TUNE_SSE_PARTIAL_REG_DEPENDENCY, "sse_partial_reg_dependency",
m_PPRO | m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_AMDFAM10
| m_BDVER | m_GENERIC)
/* X86_TUNE_SSE_SPLIT_REGS: Set for machines where the type and dependencies
are resolved on SSE register parts instead of whole registers, so we may
maintain just lower part of scalar values in proper format leaving the
upper part undefined. */
DEF_TUNE (X86_TUNE_SSE_SPLIT_REGS, "sse_split_regs", m_ATHLON_K8)
/* X86_TUNE_PARTIAL_FLAG_REG_STALL: this flag disables use of of flags
set by instructions affecting just some flags (in particular shifts).
This is because Core2 resolves dependencies on whole flags register
and such sequences introduce false dependency on previous instruction
setting full flags.
The flags does not affect generation of INC and DEC that is controlled
by X86_TUNE_USE_INCDEC.
This flag may be dropped from generic once core2-corei5 machines are
rare enough. */
DEF_TUNE (X86_TUNE_PARTIAL_FLAG_REG_STALL, "partial_flag_reg_stall",
m_CORE2 | m_GENERIC)
/* X86_TUNE_MOVX: Enable to zero extend integer registers to avoid
partial dependencies. */
DEF_TUNE (X86_TUNE_MOVX, "movx",
m_PPRO | m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT
| m_KNL | m_INTEL | m_GEODE | m_AMD_MULTIPLE | m_GENERIC)
/* X86_TUNE_MEMORY_MISMATCH_STALL: Avoid partial stores that are followed by
full sized loads. */
DEF_TUNE (X86_TUNE_MEMORY_MISMATCH_STALL, "memory_mismatch_stall",
m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT | m_INTEL
| m_KNL | m_AMD_MULTIPLE | m_GENERIC)
/* X86_TUNE_FUSE_CMP_AND_BRANCH_32: Fuse compare with a subsequent
conditional jump instruction for 32 bit TARGET.
FIXME: revisit for generic. */
DEF_TUNE (X86_TUNE_FUSE_CMP_AND_BRANCH_32, "fuse_cmp_and_branch_32",
m_CORE_ALL | m_BDVER)
/* X86_TUNE_FUSE_CMP_AND_BRANCH_64: Fuse compare with a subsequent
conditional jump instruction for TARGET_64BIT.
FIXME: revisit for generic. */
DEF_TUNE (X86_TUNE_FUSE_CMP_AND_BRANCH_64, "fuse_cmp_and_branch_64",
m_NEHALEM | m_SANDYBRIDGE | m_HASWELL | m_BDVER)
/* X86_TUNE_FUSE_CMP_AND_BRANCH_SOFLAGS: Fuse compare with a
subsequent conditional jump instruction when the condition jump
check sign flag (SF) or overflow flag (OF). */
DEF_TUNE (X86_TUNE_FUSE_CMP_AND_BRANCH_SOFLAGS, "fuse_cmp_and_branch_soflags",
m_NEHALEM | m_SANDYBRIDGE | m_HASWELL | m_BDVER)
/* X86_TUNE_FUSE_ALU_AND_BRANCH: Fuse alu with a subsequent conditional
jump instruction when the alu instruction produces the CCFLAG consumed by
the conditional jump instruction. */
DEF_TUNE (X86_TUNE_FUSE_ALU_AND_BRANCH, "fuse_alu_and_branch",
m_SANDYBRIDGE | m_HASWELL)
/* X86_TUNE_REASSOC_INT_TO_PARALLEL: Try to produce parallel computations
during reassociation of integer computation. */
DEF_TUNE (X86_TUNE_REASSOC_INT_TO_PARALLEL, "reassoc_int_to_parallel",
m_BONNELL)
/* X86_TUNE_REASSOC_FP_TO_PARALLEL: Try to produce parallel computations
during reassociation of fp computation. */
DEF_TUNE (X86_TUNE_REASSOC_FP_TO_PARALLEL, "reassoc_fp_to_parallel",
m_BONNELL | m_SILVERMONT | m_HASWELL | m_KNL |m_INTEL | m_BDVER1
| m_BDVER2 | m_GENERIC)
/*****************************************************************************/
/* Function prologue, epilogue and function calling sequences. */
/*****************************************************************************/
/* X86_TUNE_ACCUMULATE_OUTGOING_ARGS: Allocate stack space for outgoing
arguments in prologue/epilogue instead of separately for each call
by push/pop instructions.
This increase code size by about 5% in 32bit mode, less so in 64bit mode
because parameters are passed in registers. It is considerable
win for targets without stack engine that prevents multple push operations
to happen in parallel.
FIXME: the flags is incorrectly enabled for amdfam10, Bulldozer,
Bobcat and Generic. This is because disabling it causes large
regression on mgrid due to IRA limitation leading to unecessary
use of the frame pointer in 32bit mode. */
DEF_TUNE (X86_TUNE_ACCUMULATE_OUTGOING_ARGS, "accumulate_outgoing_args",
m_PPRO | m_P4_NOCONA | m_BONNELL | m_SILVERMONT | m_KNL | m_INTEL
| m_ATHLON_K8)
/* X86_TUNE_PROLOGUE_USING_MOVE: Do not use push/pop in prologues that are
considered on critical path. */
DEF_TUNE (X86_TUNE_PROLOGUE_USING_MOVE, "prologue_using_move",
m_PPRO | m_ATHLON_K8)
/* X86_TUNE_PROLOGUE_USING_MOVE: Do not use push/pop in epilogues that are
considered on critical path. */
DEF_TUNE (X86_TUNE_EPILOGUE_USING_MOVE, "epilogue_using_move",
m_PPRO | m_ATHLON_K8)
/* X86_TUNE_USE_LEAVE: Use "leave" instruction in epilogues where it fits. */
DEF_TUNE (X86_TUNE_USE_LEAVE, "use_leave",
m_386 | m_CORE_ALL | m_K6_GEODE | m_AMD_MULTIPLE | m_GENERIC)
/* X86_TUNE_PUSH_MEMORY: Enable generation of "push mem" instructions.
Some chips, like 486 and Pentium works faster with separate load
and push instructions. */
DEF_TUNE (X86_TUNE_PUSH_MEMORY, "push_memory",
m_386 | m_P4_NOCONA | m_CORE_ALL | m_K6_GEODE | m_AMD_MULTIPLE
| m_GENERIC)
/* X86_TUNE_SINGLE_PUSH: Enable if single push insn is preferred
over esp subtraction. */
DEF_TUNE (X86_TUNE_SINGLE_PUSH, "single_push", m_386 | m_486 | m_PENT
| m_K6_GEODE)
/* X86_TUNE_DOUBLE_PUSH. Enable if double push insn is preferred
over esp subtraction. */
DEF_TUNE (X86_TUNE_DOUBLE_PUSH, "double_push", m_PENT | m_K6_GEODE)
/* X86_TUNE_SINGLE_POP: Enable if single pop insn is preferred
over esp addition. */
DEF_TUNE (X86_TUNE_SINGLE_POP, "single_pop", m_386 | m_486 | m_PENT | m_PPRO)
/* X86_TUNE_DOUBLE_POP: Enable if double pop insn is preferred
over esp addition. */
DEF_TUNE (X86_TUNE_DOUBLE_POP, "double_pop", m_PENT)
/*****************************************************************************/
/* Branch predictor tuning */
/*****************************************************************************/
/* X86_TUNE_PAD_SHORT_FUNCTION: Make every function to be at least 4
instructions long. */
DEF_TUNE (X86_TUNE_PAD_SHORT_FUNCTION, "pad_short_function", m_BONNELL)
/* X86_TUNE_PAD_RETURNS: Place NOP before every RET that is a destination
of conditional jump or directly preceded by other jump instruction.
This is important for AND K8-AMDFAM10 because the branch prediction
architecture expect at most one jump per 2 byte window. Failing to
pad returns leads to misaligned return stack. */
DEF_TUNE (X86_TUNE_PAD_RETURNS, "pad_returns",
m_ATHLON_K8 | m_AMDFAM10 | m_GENERIC)
/* X86_TUNE_FOUR_JUMP_LIMIT: Some CPU cores are not able to predict more
than 4 branch instructions in the 16 byte window. */
DEF_TUNE (X86_TUNE_FOUR_JUMP_LIMIT, "four_jump_limit",
m_PPRO | m_P4_NOCONA | m_BONNELL | m_SILVERMONT | m_KNL |m_INTEL |
m_ATHLON_K8 | m_AMDFAM10)
/*****************************************************************************/
/* Integer instruction selection tuning */
/*****************************************************************************/
/* X86_TUNE_SOFTWARE_PREFETCHING_BENEFICIAL: Enable software prefetching
at -O3. For the moment, the prefetching seems badly tuned for Intel
chips. */
DEF_TUNE (X86_TUNE_SOFTWARE_PREFETCHING_BENEFICIAL, "software_prefetching_beneficial",
m_K6_GEODE | m_AMD_MULTIPLE)
/* X86_TUNE_LCP_STALL: Avoid an expensive length-changing prefix stall
on 16-bit immediate moves into memory on Core2 and Corei7. */
DEF_TUNE (X86_TUNE_LCP_STALL, "lcp_stall", m_CORE_ALL | m_GENERIC)
/* X86_TUNE_READ_MODIFY: Enable use of read-modify instructions such
as "add mem, reg". */
DEF_TUNE (X86_TUNE_READ_MODIFY, "read_modify", ~(m_PENT | m_PPRO))
/* X86_TUNE_USE_INCDEC: Enable use of inc/dec instructions. */
DEF_TUNE (X86_TUNE_USE_INCDEC, "use_incdec",
~(m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT | m_INTEL
| m_KNL | m_GENERIC))
/* X86_TUNE_INTEGER_DFMODE_MOVES: Enable if integer moves are preferred
for DFmode copies */
DEF_TUNE (X86_TUNE_INTEGER_DFMODE_MOVES, "integer_dfmode_moves",
~(m_PPRO | m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT
| m_KNL | m_INTEL | m_GEODE | m_AMD_MULTIPLE | m_GENERIC))
/* X86_TUNE_OPT_AGU: Optimize for Address Generation Unit. This flag
will impact LEA instruction selection. */
DEF_TUNE (X86_TUNE_OPT_AGU, "opt_agu", m_BONNELL | m_SILVERMONT | m_KNL
| m_INTEL)
/* X86_TUNE_AVOID_LEA_FOR_ADDR: Avoid lea for address computation. */
DEF_TUNE (X86_TUNE_AVOID_LEA_FOR_ADDR, "avoid_lea_for_addr",
m_BONNELL | m_SILVERMONT | m_KNL)
/* X86_TUNE_SLOW_IMUL_IMM32_MEM: Imul of 32-bit constant and memory is
vector path on AMD machines.
FIXME: Do we need to enable this for core? */
DEF_TUNE (X86_TUNE_SLOW_IMUL_IMM32_MEM, "slow_imul_imm32_mem",
m_K8 | m_AMDFAM10)
/* X86_TUNE_SLOW_IMUL_IMM8: Imul of 8-bit constant is vector path on AMD
machines.
FIXME: Do we need to enable this for core? */
DEF_TUNE (X86_TUNE_SLOW_IMUL_IMM8, "slow_imul_imm8",
m_K8 | m_AMDFAM10)
/* X86_TUNE_AVOID_MEM_OPND_FOR_CMOVE: Try to avoid memory operands for
a conditional move. */
DEF_TUNE (X86_TUNE_AVOID_MEM_OPND_FOR_CMOVE, "avoid_mem_opnd_for_cmove",
m_BONNELL | m_SILVERMONT | m_KNL | m_INTEL)
/* X86_TUNE_SINGLE_STRINGOP: Enable use of single string operations, such
as MOVS and STOS (without a REP prefix) to move/set sequences of bytes. */
DEF_TUNE (X86_TUNE_SINGLE_STRINGOP, "single_stringop", m_386 | m_P4_NOCONA)
/* X86_TUNE_MISALIGNED_MOVE_STRING_PRO_EPILOGUES: Enable generation of
compact prologues and epilogues by issuing a misaligned moves. This
requires target to handle misaligned moves and partial memory stalls
reasonably well.
FIXME: This may actualy be a win on more targets than listed here. */
DEF_TUNE (X86_TUNE_MISALIGNED_MOVE_STRING_PRO_EPILOGUES,
"misaligned_move_string_pro_epilogues",
m_386 | m_486 | m_CORE_ALL | m_AMD_MULTIPLE | m_GENERIC)
/* X86_TUNE_USE_SAHF: Controls use of SAHF. */
DEF_TUNE (X86_TUNE_USE_SAHF, "use_sahf",
m_PPRO | m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT
| m_KNL | m_INTEL | m_K6_GEODE | m_K8 | m_AMDFAM10 | m_BDVER
| m_BTVER | m_GENERIC)
/* X86_TUNE_USE_CLTD: Controls use of CLTD and CTQO instructions. */
DEF_TUNE (X86_TUNE_USE_CLTD, "use_cltd",
~(m_PENT | m_BONNELL | m_SILVERMONT | m_KNL | m_INTEL | m_K6))
/* X86_TUNE_USE_BT: Enable use of BT (bit test) instructions. */
DEF_TUNE (X86_TUNE_USE_BT, "use_bt",
m_CORE_ALL | m_BONNELL | m_SILVERMONT | m_KNL | m_INTEL
| m_AMD_MULTIPLE | m_GENERIC)
/*****************************************************************************/
/* 387 instruction selection tuning */
/*****************************************************************************/
/* X86_TUNE_USE_HIMODE_FIOP: Enables use of x87 instructions with 16bit
integer operand.
FIXME: Why this is disabled for modern chips? */
DEF_TUNE (X86_TUNE_USE_HIMODE_FIOP, "use_himode_fiop",
m_386 | m_486 | m_K6_GEODE)
/* X86_TUNE_USE_SIMODE_FIOP: Enables use of x87 instructions with 32bit
integer operand. */
DEF_TUNE (X86_TUNE_USE_SIMODE_FIOP, "use_simode_fiop",
~(m_PENT | m_PPRO | m_CORE_ALL | m_BONNELL | m_SILVERMONT
| m_KNL | m_INTEL | m_AMD_MULTIPLE | m_GENERIC))
/* X86_TUNE_USE_FFREEP: Use freep instruction instead of fstp. */
DEF_TUNE (X86_TUNE_USE_FFREEP, "use_ffreep", m_AMD_MULTIPLE)
/* X86_TUNE_EXT_80387_CONSTANTS: Use fancy 80387 constants, such as PI. */
DEF_TUNE (X86_TUNE_EXT_80387_CONSTANTS, "ext_80387_constants",
m_PPRO | m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT
| m_KNL | m_INTEL | m_K6_GEODE | m_ATHLON_K8 | m_GENERIC)
/*****************************************************************************/
/* SSE instruction selection tuning */
/*****************************************************************************/
/* X86_TUNE_VECTORIZE_DOUBLE: Enable double precision vector
instructions. */
DEF_TUNE (X86_TUNE_VECTORIZE_DOUBLE, "vectorize_double", ~m_BONNELL)
/* X86_TUNE_GENERAL_REGS_SSE_SPILL: Try to spill general regs to SSE
regs instead of memory. */
DEF_TUNE (X86_TUNE_GENERAL_REGS_SSE_SPILL, "general_regs_sse_spill",
m_CORE_ALL)
/* X86_TUNE_SSE_UNALIGNED_LOAD_OPTIMAL: Use movups for misaligned loads instead
of a sequence loading registers by parts. */
DEF_TUNE (X86_TUNE_SSE_UNALIGNED_LOAD_OPTIMAL, "sse_unaligned_load_optimal",
m_NEHALEM | m_SANDYBRIDGE | m_HASWELL | m_AMDFAM10 | m_BDVER
| m_BTVER | m_SILVERMONT | m_KNL | m_INTEL | m_GENERIC)
/* X86_TUNE_SSE_UNALIGNED_STORE_OPTIMAL: Use movups for misaligned stores instead
of a sequence loading registers by parts. */
DEF_TUNE (X86_TUNE_SSE_UNALIGNED_STORE_OPTIMAL, "sse_unaligned_store_optimal",
m_NEHALEM | m_SANDYBRIDGE | m_HASWELL | m_BDVER | m_SILVERMONT
| m_KNL | m_INTEL | m_GENERIC)
/* Use packed single precision instructions where posisble. I.e. movups instead
of movupd. */
DEF_TUNE (X86_TUNE_SSE_PACKED_SINGLE_INSN_OPTIMAL, "sse_packed_single_insn_optimal",
m_BDVER)
/* X86_TUNE_SSE_TYPELESS_STORES: Always movaps/movups for 128bit stores. */
DEF_TUNE (X86_TUNE_SSE_TYPELESS_STORES, "sse_typeless_stores",
m_AMD_MULTIPLE | m_CORE_ALL | m_GENERIC)
/* X86_TUNE_SSE_LOAD0_BY_PXOR: Always use pxor to load0 as opposed to
xorps/xorpd and other variants. */
DEF_TUNE (X86_TUNE_SSE_LOAD0_BY_PXOR, "sse_load0_by_pxor",
m_PPRO | m_P4_NOCONA | m_CORE_ALL | m_BDVER | m_BTVER | m_GENERIC)
/* X86_TUNE_INTER_UNIT_MOVES_TO_VEC: Enable moves in from integer
to SSE registers. If disabled, the moves will be done by storing
the value to memory and reloading. */
DEF_TUNE (X86_TUNE_INTER_UNIT_MOVES_TO_VEC, "inter_unit_moves_to_vec",
~(m_AMD_MULTIPLE | m_GENERIC))
/* X86_TUNE_INTER_UNIT_MOVES_TO_VEC: Enable moves in from SSE
to integer registers. If disabled, the moves will be done by storing
the value to memory and reloading. */
DEF_TUNE (X86_TUNE_INTER_UNIT_MOVES_FROM_VEC, "inter_unit_moves_from_vec",
~m_ATHLON_K8)
/* X86_TUNE_INTER_UNIT_CONVERSIONS: Enable float<->integer conversions
to use both SSE and integer registers at a same time.
FIXME: revisit importance of this for generic. */
DEF_TUNE (X86_TUNE_INTER_UNIT_CONVERSIONS, "inter_unit_conversions",
~(m_AMDFAM10 | m_BDVER))
/* X86_TUNE_SPLIT_MEM_OPND_FOR_FP_CONVERTS: Try to split memory operand for
fp converts to destination register. */
DEF_TUNE (X86_TUNE_SPLIT_MEM_OPND_FOR_FP_CONVERTS, "split_mem_opnd_for_fp_converts",
m_SILVERMONT | m_KNL | m_INTEL)
/* X86_TUNE_USE_VECTOR_FP_CONVERTS: Prefer vector packed SSE conversion
from FP to FP. This form of instructions avoids partial write to the
destination. */
DEF_TUNE (X86_TUNE_USE_VECTOR_FP_CONVERTS, "use_vector_fp_converts",
m_AMDFAM10)
/* X86_TUNE_USE_VECTOR_CONVERTS: Prefer vector packed SSE conversion
from integer to FP. */
DEF_TUNE (X86_TUNE_USE_VECTOR_CONVERTS, "use_vector_converts", m_AMDFAM10)
/* X86_TUNE_SLOW_SHUFB: Indicates tunings with slow pshufb instruction. */
DEF_TUNE (X86_TUNE_SLOW_PSHUFB, "slow_pshufb",
m_BONNELL | m_SILVERMONT | m_KNL | m_INTEL)
/* X86_TUNE_VECTOR_PARALLEL_EXECUTION: Indicates tunings with ability to
execute 2 or more vector instructions in parallel. */
DEF_TUNE (X86_TUNE_VECTOR_PARALLEL_EXECUTION, "vec_parallel",
m_NEHALEM | m_SANDYBRIDGE | m_HASWELL)
/* X86_TUNE_AVOID_4BYTE_PREFIXES: Avoid instructions requiring 4+ bytes of prefixes. */
DEF_TUNE (X86_TUNE_AVOID_4BYTE_PREFIXES, "avoid_4byte_prefixes",
m_SILVERMONT | m_INTEL)
/*****************************************************************************/
/* AVX instruction selection tuning (some of SSE flags affects AVX, too) */
/*****************************************************************************/
/* X86_TUNE_AVX256_UNALIGNED_LOAD_OPTIMAL: if false, unaligned loads are
split. */
DEF_TUNE (X86_TUNE_AVX256_UNALIGNED_LOAD_OPTIMAL, "256_unaligned_load_optimal",
~(m_NEHALEM | m_SANDYBRIDGE | m_GENERIC))
/* X86_TUNE_AVX256_UNALIGNED_STORE_OPTIMAL: if false, unaligned stores are
split. */
DEF_TUNE (X86_TUNE_AVX256_UNALIGNED_STORE_OPTIMAL, "256_unaligned_store_optimal",
~(m_NEHALEM | m_SANDYBRIDGE | m_BDVER | m_GENERIC))
/* X86_TUNE_AVX128_OPTIMAL: Enable 128-bit AVX instruction generation for
the auto-vectorizer. */
DEF_TUNE (X86_TUNE_AVX128_OPTIMAL, "avx128_optimal", m_BDVER | m_BTVER2)
/*****************************************************************************/
/* Historical relics: tuning flags that helps a specific old CPU designs */
/*****************************************************************************/
/* X86_TUNE_DOUBLE_WITH_ADD: Use add instead of sal to double value in
an integer register. */
DEF_TUNE (X86_TUNE_DOUBLE_WITH_ADD, "double_with_add", ~m_386)
/* X86_TUNE_ALWAYS_FANCY_MATH_387: controls use of fancy 387 operations,
such as fsqrt, fprem, fsin, fcos, fsincos etc.
Should be enabled for all targets that always has coprocesor. */
DEF_TUNE (X86_TUNE_ALWAYS_FANCY_MATH_387, "always_fancy_math_387",
~(m_386 | m_486))
/* X86_TUNE_UNROLL_STRLEN: Produce (quite lame) unrolled sequence for
inline strlen. This affects only -minline-all-stringops mode. By
default we always dispatch to a library since our internal strlen
is bad. */
DEF_TUNE (X86_TUNE_UNROLL_STRLEN, "unroll_strlen", ~m_386)
/* X86_TUNE_SHIFT1: Enables use of short encoding of "sal reg" instead of
longer "sal $1, reg". */
DEF_TUNE (X86_TUNE_SHIFT1, "shift1", ~m_486)
/* X86_TUNE_ZERO_EXTEND_WITH_AND: Use AND instruction instead
of mozbl/movwl. */
DEF_TUNE (X86_TUNE_ZERO_EXTEND_WITH_AND, "zero_extend_with_and", m_486 | m_PENT)
/* X86_TUNE_PROMOTE_HIMODE_IMUL: Modern CPUs have same latency for HImode
and SImode multiply, but 386 and 486 do HImode multiply faster. */
DEF_TUNE (X86_TUNE_PROMOTE_HIMODE_IMUL, "promote_himode_imul",
~(m_386 | m_486))
/* X86_TUNE_FAST_PREFIX: Enable demoting some 32bit or 64bit arithmetic
into 16bit/8bit when resulting sequence is shorter. For example
for "and $-65536, reg" to 16bit store of 0. */
DEF_TUNE (X86_TUNE_FAST_PREFIX, "fast_prefix", ~(m_386 | m_486 | m_PENT))
/* X86_TUNE_READ_MODIFY_WRITE: Enable use of read modify write instructions
such as "add $1, mem". */
DEF_TUNE (X86_TUNE_READ_MODIFY_WRITE, "read_modify_write", ~m_PENT)
/* X86_TUNE_MOVE_M1_VIA_OR: On pentiums, it is faster to load -1 via OR
than a MOV. */
DEF_TUNE (X86_TUNE_MOVE_M1_VIA_OR, "move_m1_via_or", m_PENT)
/* X86_TUNE_NOT_UNPAIRABLE: NOT is not pairable on Pentium, while XOR is,
but one byte longer. */
DEF_TUNE (X86_TUNE_NOT_UNPAIRABLE, "not_unpairable", m_PENT)
/* X86_TUNE_PARTIAL_REG_STALL: Pentium pro, unlike later chips, handled
use of partial registers by renaming. This improved performance of 16bit
code where upper halves of registers are not used. It also leads to
an penalty whenever a 16bit store is followed by 32bit use. This flag
disables production of such sequences in common cases.
See also X86_TUNE_HIMODE_MATH.
In current implementation the partial register stalls are not eliminated
very well - they can be introduced via subregs synthesized by combine
and can happen in caller/callee saving sequences. */
DEF_TUNE (X86_TUNE_PARTIAL_REG_STALL, "partial_reg_stall", m_PPRO)
/* X86_TUNE_PROMOTE_QIMODE: When it is cheap, turn 8bit arithmetic to
corresponding 32bit arithmetic. */
DEF_TUNE (X86_TUNE_PROMOTE_QIMODE, "promote_qimode",
~m_PPRO)
/* X86_TUNE_PROMOTE_HI_REGS: Same, but for 16bit artihmetic. Again we avoid
partial register stalls on PentiumPro targets. */
DEF_TUNE (X86_TUNE_PROMOTE_HI_REGS, "promote_hi_regs", m_PPRO)
/* X86_TUNE_HIMODE_MATH: Enable use of 16bit arithmetic.
On PPro this flag is meant to avoid partial register stalls. */
DEF_TUNE (X86_TUNE_HIMODE_MATH, "himode_math", ~m_PPRO)
/* X86_TUNE_SPLIT_LONG_MOVES: Avoid instructions moving immediates
directly to memory. */
DEF_TUNE (X86_TUNE_SPLIT_LONG_MOVES, "split_long_moves", m_PPRO)
/* X86_TUNE_USE_XCHGB: Use xchgb %rh,%rl instead of rolw/rorw $8,rx. */
DEF_TUNE (X86_TUNE_USE_XCHGB, "use_xchgb", m_PENT4)
/* X86_TUNE_USE_MOV0: Use "mov $0, reg" instead of "xor reg, reg" to clear
integer register. */
DEF_TUNE (X86_TUNE_USE_MOV0, "use_mov0", m_K6)
/* X86_TUNE_NOT_VECTORMODE: On AMD K6, NOT is vector decoded with memory
operand that cannot be represented using a modRM byte. The XOR
replacement is long decoded, so this split helps here as well. */
DEF_TUNE (X86_TUNE_NOT_VECTORMODE, "not_vectormode", m_K6)
/* X86_TUNE_AVOID_VECTOR_DECODE: Enable splitters that avoid vector decoded
forms of instructions on K8 targets. */
DEF_TUNE (X86_TUNE_AVOID_VECTOR_DECODE, "avoid_vector_decode",
m_K8)
/* X86_TUNE_AVOID_FALSE_DEP_FOR_BMI: Avoid false dependency
for bit-manipulation instructions. */
DEF_TUNE (X86_TUNE_AVOID_FALSE_DEP_FOR_BMI, "avoid_false_dep_for_bmi",
m_SANDYBRIDGE | m_HASWELL | m_GENERIC)
/*****************************************************************************/
/* This never worked well before. */
/*****************************************************************************/
/* X86_TUNE_BRANCH_PREDICTION_HINTS: Branch hints were put in P4 based
on simulation result. But after P4 was made, no performance benefit
was observed with branch hints. It also increases the code size.
As a result, icc never generates branch hints. */
DEF_TUNE (X86_TUNE_BRANCH_PREDICTION_HINTS, "branch_prediction_hints", 0)
/* X86_TUNE_QIMODE_MATH: Enable use of 8bit arithmetic. */
DEF_TUNE (X86_TUNE_QIMODE_MATH, "qimode_math", ~0)
/* X86_TUNE_PROMOTE_QI_REGS: This enables generic code that promotes all 8bit
arithmetic to 32bit via PROMOTE_MODE macro. This code generation scheme
is usually used for RISC targets. */
DEF_TUNE (X86_TUNE_PROMOTE_QI_REGS, "promote_qi_regs", 0)
/* X86_TUNE_ADJUST_UNROLL: This enables adjusting the unroll factor based
on hardware capabilities. Bdver3 hardware has a loop buffer which makes
unrolling small loop less important. For, such architectures we adjust
the unroll factor so that the unrolled loop fits the loop buffer. */
DEF_TUNE (X86_TUNE_ADJUST_UNROLL, "adjust_unroll_factor", m_BDVER3 | m_BDVER4)