1 /* Definitions of x86 tunable features.
2 Copyright (C) 2013-2014 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
11 GCC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License and
17 a copy of the GCC Runtime Library Exception along with this program;
18 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
19 <http://www.gnu.org/licenses/>. */
21 /* Tuning for a given CPU XXXX consists of:
22 - adding new CPU into:
23 - adding PROCESSOR_XXX to processor_type (in i386.h)
24 - possibly adding XXX into CPU attribute in i386.md
25 - adding XXX to processor_alias_table (in i386.c)
26 - introducing ix86_XXX_cost in i386.c
27 - Stringop generation table can be build based on test_stringop
28 - script (once rest of tuning is complete)
29 - designing a scheduler model in
31 - Updating ix86_issue_rate and ix86_adjust_cost in i386.md
32 - possibly updating ia32_multipass_dfa_lookahead, ix86_sched_reorder
33 and ix86_sched_init_global if those tricks are needed.
34 - Tunning the flags bellow. Those are split into sections and each
35 section is very roughly ordered by importance. */
37 /*****************************************************************************/
38 /* Scheduling flags. */
39 /*****************************************************************************/
41 /* X86_TUNE_SCHEDULE: Enable scheduling. */
42 DEF_TUNE (X86_TUNE_SCHEDULE, "schedule",
43 m_PENT | m_PPRO | m_CORE_ALL | m_BONNELL | m_SILVERMONT | m_INTEL
44 | m_K6_GEODE | m_AMD_MULTIPLE | m_GENERIC)
46 /* X86_TUNE_PARTIAL_REG_DEPENDENCY: Enable more register renaming
47 on modern chips. Preffer stores affecting whole integer register
48 over partial stores. For example preffer MOVZBL or MOVQ to load 8bit
50 DEF_TUNE (X86_TUNE_PARTIAL_REG_DEPENDENCY, "partial_reg_dependency",
51 m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT | m_INTEL
52 | m_AMD_MULTIPLE | m_GENERIC)
54 /* X86_TUNE_SSE_PARTIAL_REG_DEPENDENCY: This knob promotes all store
55 destinations to be 128bit to allow register renaming on 128bit SSE units,
56 but usually results in one extra microop on 64bit SSE units.
57 Experimental results shows that disabling this option on P4 brings over 20%
58 SPECfp regression, while enabling it on K8 brings roughly 2.4% regression
59 that can be partly masked by careful scheduling of moves. */
60 DEF_TUNE (X86_TUNE_SSE_PARTIAL_REG_DEPENDENCY, "sse_partial_reg_dependency",
61 m_PPRO | m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_AMDFAM10
62 | m_BDVER | m_GENERIC)
64 /* X86_TUNE_SSE_SPLIT_REGS: Set for machines where the type and dependencies
65 are resolved on SSE register parts instead of whole registers, so we may
66 maintain just lower part of scalar values in proper format leaving the
67 upper part undefined. */
68 DEF_TUNE (X86_TUNE_SSE_SPLIT_REGS, "sse_split_regs", m_ATHLON_K8)
70 /* X86_TUNE_PARTIAL_FLAG_REG_STALL: this flag disables use of of flags
71 set by instructions affecting just some flags (in particular shifts).
72 This is because Core2 resolves dependencies on whole flags register
73 and such sequences introduce false dependency on previous instruction
76 The flags does not affect generation of INC and DEC that is controlled
77 by X86_TUNE_USE_INCDEC.
79 This flag may be dropped from generic once core2-corei5 machines are
81 DEF_TUNE (X86_TUNE_PARTIAL_FLAG_REG_STALL, "partial_flag_reg_stall",
84 /* X86_TUNE_MOVX: Enable to zero extend integer registers to avoid
85 partial dependencies. */
86 DEF_TUNE (X86_TUNE_MOVX, "movx",
87 m_PPRO | m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT
88 | m_INTEL | m_GEODE | m_AMD_MULTIPLE | m_GENERIC)
90 /* X86_TUNE_MEMORY_MISMATCH_STALL: Avoid partial stores that are followed by
92 DEF_TUNE (X86_TUNE_MEMORY_MISMATCH_STALL, "memory_mismatch_stall",
93 m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT | m_INTEL
94 | m_AMD_MULTIPLE | m_GENERIC)
96 /* X86_TUNE_FUSE_CMP_AND_BRANCH_32: Fuse compare with a subsequent
97 conditional jump instruction for 32 bit TARGET.
98 FIXME: revisit for generic. */
99 DEF_TUNE (X86_TUNE_FUSE_CMP_AND_BRANCH_32, "fuse_cmp_and_branch_32",
100 m_CORE_ALL | m_BDVER)
102 /* X86_TUNE_FUSE_CMP_AND_BRANCH_64: Fuse compare with a subsequent
103 conditional jump instruction for TARGET_64BIT.
104 FIXME: revisit for generic. */
105 DEF_TUNE (X86_TUNE_FUSE_CMP_AND_BRANCH_64, "fuse_cmp_and_branch_64",
106 m_NEHALEM | m_SANDYBRIDGE | m_HASWELL | m_BDVER)
108 /* X86_TUNE_FUSE_CMP_AND_BRANCH_SOFLAGS: Fuse compare with a
109 subsequent conditional jump instruction when the condition jump
110 check sign flag (SF) or overflow flag (OF). */
111 DEF_TUNE (X86_TUNE_FUSE_CMP_AND_BRANCH_SOFLAGS, "fuse_cmp_and_branch_soflags",
112 m_NEHALEM | m_SANDYBRIDGE | m_HASWELL | m_BDVER)
114 /* X86_TUNE_FUSE_ALU_AND_BRANCH: Fuse alu with a subsequent conditional
115 jump instruction when the alu instruction produces the CCFLAG consumed by
116 the conditional jump instruction. */
117 DEF_TUNE (X86_TUNE_FUSE_ALU_AND_BRANCH, "fuse_alu_and_branch",
118 m_SANDYBRIDGE | m_HASWELL)
120 /* X86_TUNE_REASSOC_INT_TO_PARALLEL: Try to produce parallel computations
121 during reassociation of integer computation. */
122 DEF_TUNE (X86_TUNE_REASSOC_INT_TO_PARALLEL, "reassoc_int_to_parallel",
125 /* X86_TUNE_REASSOC_FP_TO_PARALLEL: Try to produce parallel computations
126 during reassociation of fp computation. */
127 DEF_TUNE (X86_TUNE_REASSOC_FP_TO_PARALLEL, "reassoc_fp_to_parallel",
128 m_BONNELL | m_SILVERMONT | m_HASWELL | m_INTEL | m_BDVER1
129 | m_BDVER2 | m_GENERIC)
131 /*****************************************************************************/
132 /* Function prologue, epilogue and function calling sequences. */
133 /*****************************************************************************/
135 /* X86_TUNE_ACCUMULATE_OUTGOING_ARGS: Allocate stack space for outgoing
136 arguments in prologue/epilogue instead of separately for each call
137 by push/pop instructions.
138 This increase code size by about 5% in 32bit mode, less so in 64bit mode
139 because parameters are passed in registers. It is considerable
140 win for targets without stack engine that prevents multple push operations
141 to happen in parallel.
143 FIXME: the flags is incorrectly enabled for amdfam10, Bulldozer,
144 Bobcat and Generic. This is because disabling it causes large
145 regression on mgrid due to IRA limitation leading to unecessary
146 use of the frame pointer in 32bit mode. */
147 DEF_TUNE (X86_TUNE_ACCUMULATE_OUTGOING_ARGS, "accumulate_outgoing_args",
148 m_PPRO | m_P4_NOCONA | m_BONNELL | m_SILVERMONT | m_INTEL
151 /* X86_TUNE_PROLOGUE_USING_MOVE: Do not use push/pop in prologues that are
152 considered on critical path. */
153 DEF_TUNE (X86_TUNE_PROLOGUE_USING_MOVE, "prologue_using_move",
154 m_PPRO | m_ATHLON_K8)
156 /* X86_TUNE_PROLOGUE_USING_MOVE: Do not use push/pop in epilogues that are
157 considered on critical path. */
158 DEF_TUNE (X86_TUNE_EPILOGUE_USING_MOVE, "epilogue_using_move",
159 m_PPRO | m_ATHLON_K8)
161 /* X86_TUNE_USE_LEAVE: Use "leave" instruction in epilogues where it fits. */
162 DEF_TUNE (X86_TUNE_USE_LEAVE, "use_leave",
163 m_386 | m_CORE_ALL | m_K6_GEODE | m_AMD_MULTIPLE | m_GENERIC)
165 /* X86_TUNE_PUSH_MEMORY: Enable generation of "push mem" instructions.
166 Some chips, like 486 and Pentium works faster with separate load
167 and push instructions. */
168 DEF_TUNE (X86_TUNE_PUSH_MEMORY, "push_memory",
169 m_386 | m_P4_NOCONA | m_CORE_ALL | m_K6_GEODE | m_AMD_MULTIPLE
172 /* X86_TUNE_SINGLE_PUSH: Enable if single push insn is preferred
173 over esp subtraction. */
174 DEF_TUNE (X86_TUNE_SINGLE_PUSH, "single_push", m_386 | m_486 | m_PENT
177 /* X86_TUNE_DOUBLE_PUSH. Enable if double push insn is preferred
178 over esp subtraction. */
179 DEF_TUNE (X86_TUNE_DOUBLE_PUSH, "double_push", m_PENT | m_K6_GEODE)
181 /* X86_TUNE_SINGLE_POP: Enable if single pop insn is preferred
182 over esp addition. */
183 DEF_TUNE (X86_TUNE_SINGLE_POP, "single_pop", m_386 | m_486 | m_PENT | m_PPRO)
185 /* X86_TUNE_DOUBLE_POP: Enable if double pop insn is preferred
186 over esp addition. */
187 DEF_TUNE (X86_TUNE_DOUBLE_POP, "double_pop", m_PENT)
189 /*****************************************************************************/
190 /* Branch predictor tuning */
191 /*****************************************************************************/
193 /* X86_TUNE_PAD_SHORT_FUNCTION: Make every function to be at least 4
194 instructions long. */
195 DEF_TUNE (X86_TUNE_PAD_SHORT_FUNCTION, "pad_short_function", m_BONNELL)
197 /* X86_TUNE_PAD_RETURNS: Place NOP before every RET that is a destination
198 of conditional jump or directly preceded by other jump instruction.
199 This is important for AND K8-AMDFAM10 because the branch prediction
200 architecture expect at most one jump per 2 byte window. Failing to
201 pad returns leads to misaligned return stack. */
202 DEF_TUNE (X86_TUNE_PAD_RETURNS, "pad_returns",
203 m_ATHLON_K8 | m_AMDFAM10 | m_GENERIC)
205 /* X86_TUNE_FOUR_JUMP_LIMIT: Some CPU cores are not able to predict more
206 than 4 branch instructions in the 16 byte window. */
207 DEF_TUNE (X86_TUNE_FOUR_JUMP_LIMIT, "four_jump_limit",
208 m_PPRO | m_P4_NOCONA | m_BONNELL | m_SILVERMONT | m_INTEL |
209 m_ATHLON_K8 | m_AMDFAM10)
211 /*****************************************************************************/
212 /* Integer instruction selection tuning */
213 /*****************************************************************************/
215 /* X86_TUNE_SOFTWARE_PREFETCHING_BENEFICIAL: Enable software prefetching
216 at -O3. For the moment, the prefetching seems badly tuned for Intel
218 DEF_TUNE (X86_TUNE_SOFTWARE_PREFETCHING_BENEFICIAL, "software_prefetching_beneficial",
219 m_K6_GEODE | m_AMD_MULTIPLE)
221 /* X86_TUNE_LCP_STALL: Avoid an expensive length-changing prefix stall
222 on 16-bit immediate moves into memory on Core2 and Corei7. */
223 DEF_TUNE (X86_TUNE_LCP_STALL, "lcp_stall", m_CORE_ALL | m_GENERIC)
225 /* X86_TUNE_READ_MODIFY: Enable use of read-modify instructions such
226 as "add mem, reg". */
227 DEF_TUNE (X86_TUNE_READ_MODIFY, "read_modify", ~(m_PENT | m_PPRO))
229 /* X86_TUNE_USE_INCDEC: Enable use of inc/dec instructions. */
230 DEF_TUNE (X86_TUNE_USE_INCDEC, "use_incdec",
231 ~(m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT | m_INTEL
234 /* X86_TUNE_INTEGER_DFMODE_MOVES: Enable if integer moves are preferred
236 DEF_TUNE (X86_TUNE_INTEGER_DFMODE_MOVES, "integer_dfmode_moves",
237 ~(m_PPRO | m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT
238 | m_INTEL | m_GEODE | m_AMD_MULTIPLE | m_GENERIC))
240 /* X86_TUNE_OPT_AGU: Optimize for Address Generation Unit. This flag
241 will impact LEA instruction selection. */
242 DEF_TUNE (X86_TUNE_OPT_AGU, "opt_agu", m_BONNELL | m_SILVERMONT | m_INTEL)
244 /* X86_TUNE_AVOID_LEA_FOR_ADDR: Avoid lea for address computation. */
245 DEF_TUNE (X86_TUNE_AVOID_LEA_FOR_ADDR, "avoid_lea_for_addr",
246 m_BONNELL | m_SILVERMONT)
248 /* X86_TUNE_SLOW_IMUL_IMM32_MEM: Imul of 32-bit constant and memory is
249 vector path on AMD machines.
250 FIXME: Do we need to enable this for core? */
251 DEF_TUNE (X86_TUNE_SLOW_IMUL_IMM32_MEM, "slow_imul_imm32_mem",
254 /* X86_TUNE_SLOW_IMUL_IMM8: Imul of 8-bit constant is vector path on AMD
256 FIXME: Do we need to enable this for core? */
257 DEF_TUNE (X86_TUNE_SLOW_IMUL_IMM8, "slow_imul_imm8",
260 /* X86_TUNE_AVOID_MEM_OPND_FOR_CMOVE: Try to avoid memory operands for
261 a conditional move. */
262 DEF_TUNE (X86_TUNE_AVOID_MEM_OPND_FOR_CMOVE, "avoid_mem_opnd_for_cmove",
263 m_BONNELL | m_SILVERMONT | m_INTEL)
265 /* X86_TUNE_SINGLE_STRINGOP: Enable use of single string operations, such
266 as MOVS and STOS (without a REP prefix) to move/set sequences of bytes. */
267 DEF_TUNE (X86_TUNE_SINGLE_STRINGOP, "single_stringop", m_386 | m_P4_NOCONA)
269 /* X86_TUNE_MISALIGNED_MOVE_STRING_PRO_EPILOGUES: Enable generation of
270 compact prologues and epilogues by issuing a misaligned moves. This
271 requires target to handle misaligned moves and partial memory stalls
273 FIXME: This may actualy be a win on more targets than listed here. */
274 DEF_TUNE (X86_TUNE_MISALIGNED_MOVE_STRING_PRO_EPILOGUES,
275 "misaligned_move_string_pro_epilogues",
276 m_386 | m_486 | m_CORE_ALL | m_AMD_MULTIPLE | m_GENERIC)
278 /* X86_TUNE_USE_SAHF: Controls use of SAHF. */
279 DEF_TUNE (X86_TUNE_USE_SAHF, "use_sahf",
280 m_PPRO | m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT
281 | m_INTEL | m_K6_GEODE | m_K8 | m_AMDFAM10 | m_BDVER | m_BTVER
284 /* X86_TUNE_USE_CLTD: Controls use of CLTD and CTQO instructions. */
285 DEF_TUNE (X86_TUNE_USE_CLTD, "use_cltd",
286 ~(m_PENT | m_BONNELL | m_SILVERMONT | m_INTEL | m_K6))
288 /* X86_TUNE_USE_BT: Enable use of BT (bit test) instructions. */
289 DEF_TUNE (X86_TUNE_USE_BT, "use_bt",
290 m_CORE_ALL | m_BONNELL | m_SILVERMONT | m_INTEL | m_AMD_MULTIPLE
293 /*****************************************************************************/
294 /* 387 instruction selection tuning */
295 /*****************************************************************************/
297 /* X86_TUNE_USE_HIMODE_FIOP: Enables use of x87 instructions with 16bit
299 FIXME: Why this is disabled for modern chips? */
300 DEF_TUNE (X86_TUNE_USE_HIMODE_FIOP, "use_himode_fiop",
301 m_386 | m_486 | m_K6_GEODE)
303 /* X86_TUNE_USE_SIMODE_FIOP: Enables use of x87 instructions with 32bit
305 DEF_TUNE (X86_TUNE_USE_SIMODE_FIOP, "use_simode_fiop",
306 ~(m_PENT | m_PPRO | m_CORE_ALL | m_BONNELL | m_SILVERMONT
307 | m_INTEL | m_AMD_MULTIPLE | m_GENERIC))
309 /* X86_TUNE_USE_FFREEP: Use freep instruction instead of fstp. */
310 DEF_TUNE (X86_TUNE_USE_FFREEP, "use_ffreep", m_AMD_MULTIPLE)
312 /* X86_TUNE_EXT_80387_CONSTANTS: Use fancy 80387 constants, such as PI. */
313 DEF_TUNE (X86_TUNE_EXT_80387_CONSTANTS, "ext_80387_constants",
314 m_PPRO | m_P4_NOCONA | m_CORE_ALL | m_BONNELL | m_SILVERMONT
315 | m_INTEL | m_K6_GEODE | m_ATHLON_K8 | m_GENERIC)
317 /*****************************************************************************/
318 /* SSE instruction selection tuning */
319 /*****************************************************************************/
321 /* X86_TUNE_VECTORIZE_DOUBLE: Enable double precision vector
323 DEF_TUNE (X86_TUNE_VECTORIZE_DOUBLE, "vectorize_double", ~m_BONNELL)
325 /* X86_TUNE_GENERAL_REGS_SSE_SPILL: Try to spill general regs to SSE
326 regs instead of memory. */
327 DEF_TUNE (X86_TUNE_GENERAL_REGS_SSE_SPILL, "general_regs_sse_spill",
330 /* X86_TUNE_SSE_UNALIGNED_LOAD_OPTIMAL: Use movups for misaligned loads instead
331 of a sequence loading registers by parts. */
332 DEF_TUNE (X86_TUNE_SSE_UNALIGNED_LOAD_OPTIMAL, "sse_unaligned_load_optimal",
333 m_NEHALEM | m_SANDYBRIDGE | m_HASWELL | m_AMDFAM10 | m_BDVER
334 | m_BTVER | m_SILVERMONT | m_INTEL | m_GENERIC)
336 /* X86_TUNE_SSE_UNALIGNED_STORE_OPTIMAL: Use movups for misaligned stores instead
337 of a sequence loading registers by parts. */
338 DEF_TUNE (X86_TUNE_SSE_UNALIGNED_STORE_OPTIMAL, "sse_unaligned_store_optimal",
339 m_NEHALEM | m_SANDYBRIDGE | m_HASWELL | m_BDVER | m_SILVERMONT
340 | m_INTEL | m_GENERIC)
342 /* Use packed single precision instructions where posisble. I.e. movups instead
344 DEF_TUNE (X86_TUNE_SSE_PACKED_SINGLE_INSN_OPTIMAL, "sse_packed_single_insn_optimal",
347 /* X86_TUNE_SSE_TYPELESS_STORES: Always movaps/movups for 128bit stores. */
348 DEF_TUNE (X86_TUNE_SSE_TYPELESS_STORES, "sse_typeless_stores",
349 m_AMD_MULTIPLE | m_CORE_ALL | m_GENERIC)
351 /* X86_TUNE_SSE_LOAD0_BY_PXOR: Always use pxor to load0 as opposed to
352 xorps/xorpd and other variants. */
353 DEF_TUNE (X86_TUNE_SSE_LOAD0_BY_PXOR, "sse_load0_by_pxor",
354 m_PPRO | m_P4_NOCONA | m_CORE_ALL | m_BDVER | m_BTVER | m_GENERIC)
356 /* X86_TUNE_INTER_UNIT_MOVES_TO_VEC: Enable moves in from integer
357 to SSE registers. If disabled, the moves will be done by storing
358 the value to memory and reloading. */
359 DEF_TUNE (X86_TUNE_INTER_UNIT_MOVES_TO_VEC, "inter_unit_moves_to_vec",
360 ~(m_AMD_MULTIPLE | m_GENERIC))
362 /* X86_TUNE_INTER_UNIT_MOVES_TO_VEC: Enable moves in from SSE
363 to integer registers. If disabled, the moves will be done by storing
364 the value to memory and reloading. */
365 DEF_TUNE (X86_TUNE_INTER_UNIT_MOVES_FROM_VEC, "inter_unit_moves_from_vec",
368 /* X86_TUNE_INTER_UNIT_CONVERSIONS: Enable float<->integer conversions
369 to use both SSE and integer registers at a same time.
370 FIXME: revisit importance of this for generic. */
371 DEF_TUNE (X86_TUNE_INTER_UNIT_CONVERSIONS, "inter_unit_conversions",
372 ~(m_AMDFAM10 | m_BDVER))
374 /* X86_TUNE_SPLIT_MEM_OPND_FOR_FP_CONVERTS: Try to split memory operand for
375 fp converts to destination register. */
376 DEF_TUNE (X86_TUNE_SPLIT_MEM_OPND_FOR_FP_CONVERTS, "split_mem_opnd_for_fp_converts",
377 m_SILVERMONT | m_INTEL)
379 /* X86_TUNE_USE_VECTOR_FP_CONVERTS: Prefer vector packed SSE conversion
380 from FP to FP. This form of instructions avoids partial write to the
382 DEF_TUNE (X86_TUNE_USE_VECTOR_FP_CONVERTS, "use_vector_fp_converts",
385 /* X86_TUNE_USE_VECTOR_CONVERTS: Prefer vector packed SSE conversion
386 from integer to FP. */
387 DEF_TUNE (X86_TUNE_USE_VECTOR_CONVERTS, "use_vector_converts", m_AMDFAM10)
389 /* X86_TUNE_SLOW_SHUFB: Indicates tunings with slow pshufb instruction. */
390 DEF_TUNE (X86_TUNE_SLOW_PSHUFB, "slow_pshufb",
391 m_BONNELL | m_SILVERMONT | m_INTEL)
393 /* X86_TUNE_VECTOR_PARALLEL_EXECUTION: Indicates tunings with ability to
394 execute 2 or more vector instructions in parallel. */
395 DEF_TUNE (X86_TUNE_VECTOR_PARALLEL_EXECUTION, "vec_parallel",
396 m_NEHALEM | m_SANDYBRIDGE | m_HASWELL)
398 /* X86_TUNE_AVOID_4BYTE_PREFIXES: Avoid instructions requiring 4+ bytes of prefixes. */
399 DEF_TUNE (X86_TUNE_AVOID_4BYTE_PREFIXES, "avoid_4byte_prefixes",
400 m_SILVERMONT | m_INTEL)
402 /*****************************************************************************/
403 /* AVX instruction selection tuning (some of SSE flags affects AVX, too) */
404 /*****************************************************************************/
406 /* X86_TUNE_AVX256_UNALIGNED_LOAD_OPTIMAL: if false, unaligned loads are
408 DEF_TUNE (X86_TUNE_AVX256_UNALIGNED_LOAD_OPTIMAL, "256_unaligned_load_optimal",
409 ~(m_NEHALEM | m_SANDYBRIDGE | m_GENERIC))
411 /* X86_TUNE_AVX256_UNALIGNED_STORE_OPTIMAL: if false, unaligned stores are
413 DEF_TUNE (X86_TUNE_AVX256_UNALIGNED_STORE_OPTIMAL, "256_unaligned_store_optimal",
414 ~(m_NEHALEM | m_SANDYBRIDGE | m_BDVER | m_GENERIC))
416 /* X86_TUNE_AVX128_OPTIMAL: Enable 128-bit AVX instruction generation for
417 the auto-vectorizer. */
418 DEF_TUNE (X86_TUNE_AVX128_OPTIMAL, "avx128_optimal", m_BDVER | m_BTVER2)
420 /*****************************************************************************/
421 /* Historical relics: tuning flags that helps a specific old CPU designs */
422 /*****************************************************************************/
424 /* X86_TUNE_DOUBLE_WITH_ADD: Use add instead of sal to double value in
425 an integer register. */
426 DEF_TUNE (X86_TUNE_DOUBLE_WITH_ADD, "double_with_add", ~m_386)
428 /* X86_TUNE_ALWAYS_FANCY_MATH_387: controls use of fancy 387 operations,
429 such as fsqrt, fprem, fsin, fcos, fsincos etc.
430 Should be enabled for all targets that always has coprocesor. */
431 DEF_TUNE (X86_TUNE_ALWAYS_FANCY_MATH_387, "always_fancy_math_387",
434 /* X86_TUNE_UNROLL_STRLEN: Produce (quite lame) unrolled sequence for
435 inline strlen. This affects only -minline-all-stringops mode. By
436 default we always dispatch to a library since our internal strlen
438 DEF_TUNE (X86_TUNE_UNROLL_STRLEN, "unroll_strlen", ~m_386)
440 /* X86_TUNE_SHIFT1: Enables use of short encoding of "sal reg" instead of
441 longer "sal $1, reg". */
442 DEF_TUNE (X86_TUNE_SHIFT1, "shift1", ~m_486)
444 /* X86_TUNE_ZERO_EXTEND_WITH_AND: Use AND instruction instead
446 DEF_TUNE (X86_TUNE_ZERO_EXTEND_WITH_AND, "zero_extend_with_and", m_486 | m_PENT)
448 /* X86_TUNE_PROMOTE_HIMODE_IMUL: Modern CPUs have same latency for HImode
449 and SImode multiply, but 386 and 486 do HImode multiply faster. */
450 DEF_TUNE (X86_TUNE_PROMOTE_HIMODE_IMUL, "promote_himode_imul",
453 /* X86_TUNE_FAST_PREFIX: Enable demoting some 32bit or 64bit arithmetic
454 into 16bit/8bit when resulting sequence is shorter. For example
455 for "and $-65536, reg" to 16bit store of 0. */
456 DEF_TUNE (X86_TUNE_FAST_PREFIX, "fast_prefix", ~(m_386 | m_486 | m_PENT))
458 /* X86_TUNE_READ_MODIFY_WRITE: Enable use of read modify write instructions
459 such as "add $1, mem". */
460 DEF_TUNE (X86_TUNE_READ_MODIFY_WRITE, "read_modify_write", ~m_PENT)
462 /* X86_TUNE_MOVE_M1_VIA_OR: On pentiums, it is faster to load -1 via OR
464 DEF_TUNE (X86_TUNE_MOVE_M1_VIA_OR, "move_m1_via_or", m_PENT)
466 /* X86_TUNE_NOT_UNPAIRABLE: NOT is not pairable on Pentium, while XOR is,
467 but one byte longer. */
468 DEF_TUNE (X86_TUNE_NOT_UNPAIRABLE, "not_unpairable", m_PENT)
470 /* X86_TUNE_PARTIAL_REG_STALL: Pentium pro, unlike later chips, handled
471 use of partial registers by renaming. This improved performance of 16bit
472 code where upper halves of registers are not used. It also leads to
473 an penalty whenever a 16bit store is followed by 32bit use. This flag
474 disables production of such sequences in common cases.
475 See also X86_TUNE_HIMODE_MATH.
477 In current implementation the partial register stalls are not eliminated
478 very well - they can be introduced via subregs synthesized by combine
479 and can happen in caller/callee saving sequences. */
480 DEF_TUNE (X86_TUNE_PARTIAL_REG_STALL, "partial_reg_stall", m_PPRO)
482 /* X86_TUNE_PROMOTE_QIMODE: When it is cheap, turn 8bit arithmetic to
483 corresponding 32bit arithmetic. */
484 DEF_TUNE (X86_TUNE_PROMOTE_QIMODE, "promote_qimode",
487 /* X86_TUNE_PROMOTE_HI_REGS: Same, but for 16bit artihmetic. Again we avoid
488 partial register stalls on PentiumPro targets. */
489 DEF_TUNE (X86_TUNE_PROMOTE_HI_REGS, "promote_hi_regs", m_PPRO)
491 /* X86_TUNE_HIMODE_MATH: Enable use of 16bit arithmetic.
492 On PPro this flag is meant to avoid partial register stalls. */
493 DEF_TUNE (X86_TUNE_HIMODE_MATH, "himode_math", ~m_PPRO)
495 /* X86_TUNE_SPLIT_LONG_MOVES: Avoid instructions moving immediates
496 directly to memory. */
497 DEF_TUNE (X86_TUNE_SPLIT_LONG_MOVES, "split_long_moves", m_PPRO)
499 /* X86_TUNE_USE_XCHGB: Use xchgb %rh,%rl instead of rolw/rorw $8,rx. */
500 DEF_TUNE (X86_TUNE_USE_XCHGB, "use_xchgb", m_PENT4)
502 /* X86_TUNE_USE_MOV0: Use "mov $0, reg" instead of "xor reg, reg" to clear
504 DEF_TUNE (X86_TUNE_USE_MOV0, "use_mov0", m_K6)
506 /* X86_TUNE_NOT_VECTORMODE: On AMD K6, NOT is vector decoded with memory
507 operand that cannot be represented using a modRM byte. The XOR
508 replacement is long decoded, so this split helps here as well. */
509 DEF_TUNE (X86_TUNE_NOT_VECTORMODE, "not_vectormode", m_K6)
511 /* X86_TUNE_AVOID_VECTOR_DECODE: Enable splitters that avoid vector decoded
512 forms of instructions on K8 targets. */
513 DEF_TUNE (X86_TUNE_AVOID_VECTOR_DECODE, "avoid_vector_decode",
516 /* X86_TUNE_AVOID_FALSE_DEP_FOR_BMI: Avoid false dependency
517 for bit-manipulation instructions. */
518 DEF_TUNE (X86_TUNE_AVOID_FALSE_DEP_FOR_BMI, "avoid_false_dep_for_bmi",
519 m_SANDYBRIDGE | m_HASWELL | m_GENERIC)
521 /*****************************************************************************/
522 /* This never worked well before. */
523 /*****************************************************************************/
525 /* X86_TUNE_BRANCH_PREDICTION_HINTS: Branch hints were put in P4 based
526 on simulation result. But after P4 was made, no performance benefit
527 was observed with branch hints. It also increases the code size.
528 As a result, icc never generates branch hints. */
529 DEF_TUNE (X86_TUNE_BRANCH_PREDICTION_HINTS, "branch_prediction_hints", 0)
531 /* X86_TUNE_QIMODE_MATH: Enable use of 8bit arithmetic. */
532 DEF_TUNE (X86_TUNE_QIMODE_MATH, "qimode_math", ~0)
534 /* X86_TUNE_PROMOTE_QI_REGS: This enables generic code that promotes all 8bit
535 arithmetic to 32bit via PROMOTE_MODE macro. This code generation scheme
536 is usually used for RISC targets. */
537 DEF_TUNE (X86_TUNE_PROMOTE_QI_REGS, "promote_qi_regs", 0)
539 /* X86_TUNE_ADJUST_UNROLL: This enables adjusting the unroll factor based
540 on hardware capabilities. Bdver3 hardware has a loop buffer which makes
541 unrolling small loop less important. For, such architectures we adjust
542 the unroll factor so that the unrolled loop fits the loop buffer. */
543 DEF_TUNE (X86_TUNE_ADJUST_UNROLL, "adjust_unroll_factor", m_BDVER3 | m_BDVER4)