Patchwork Document x86-tune options

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Submitter Jan Hubicka
Date Sept. 29, 2013, 12:18 p.m.
Message ID <20130929121823.GA24292@kam.mff.cuni.cz>
Download mbox | patch
Permalink /patch/278862/
State New
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Comments

Jan Hubicka - Sept. 29, 2013, 12:18 p.m.
Hi,
this patch adds documetnation to individual options and also adds vertical whitespace.

Comitted as obvious,
Honza
	* config/i386/x86-tune.def: Add documentation for each of the options;
	add whitespace.

Patch

Index: config/i386/x86-tune.def
===================================================================
--- config/i386/x86-tune.def	(revision 203012)
+++ config/i386/x86-tune.def	(working copy)
@@ -24,207 +24,378 @@  see the files COPYING3 and COPYING.RUNTI
    work well with PPro base chips.  */
 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 have problems with these sequences.  */
 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_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_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_486 | m_PENT | m_PPRO | m_ATOM | m_SLM | m_CORE_ALL | m_K6
 	 | m_AMD_MULTIPLE | m_GENERIC)
+
 /* 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_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_USE_SAHF: Controls use of SAHF.  */
 DEF_TUNE (X86_TUNE_USE_SAHF, "use_sahf",
           m_PPRO | m_P4_NOCONA | m_CORE_ALL | m_ATOM | m_SLM | m_K6_GEODE
           | m_K8 | m_AMDFAM10 | m_BDVER | m_BTVER | 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_ATOM | m_SLM | m_GEODE 
           | m_AMD_MULTIPLE  | m_GENERIC)
-/* X86_TUNE_PARTIAL_REG_STALL: We probably ought to watch for partial
-   register stalls on Generic32 compilation setting as well.  However
-   in current implementation the partial register stalls are not eliminated
+
+/* 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_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_LCP_STALL: Avoid an expensive length-changing prefix stall
- * on 16-bit immediate moves into memory on Core2 and Corei7.  */
+   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_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_ATOM 
             | m_SLM | m_AMD_MULTIPLE | m_GENERIC))
+
+/* 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_USE_CLTD: Controls use of CLTD and CTQO instructions.  */
 DEF_TUNE (X86_TUNE_USE_CLTD, "use_cltd", ~(m_PENT | m_ATOM | m_SLM | m_K6))
+
 /* 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_SPLIT_LONG_MOVES: Avoid instructions moving immediates
+   directly to memory.  */
 DEF_TUNE (X86_TUNE_SPLIT_LONG_MOVES, "split_long_moves", m_PPRO)
+
+/* 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_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_PROMOTE_QIMODE: When it is cheap, turn 8bit arithmetic to
+   corresponding 32bit arithmetic.  */
 DEF_TUNE (X86_TUNE_PROMOTE_QIMODE, "promote_qimode",
           m_386 | m_486 | m_PENT | m_CORE_ALL | m_ATOM | m_SLM 
           | m_K6_GEODE | m_AMD_MULTIPLE | m_GENERIC)
+
+/* 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_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_QIMODE_MATH: Enable use of 8bit arithmetic.  */
 DEF_TUNE (X86_TUNE_QIMODE_MATH, "qimode_math", ~0)
-/* X86_TUNE_HIMODE_MATH: On PPro this flag is meant to avoid partial
-   register stalls.  Just like X86_TUNE_PARTIAL_REG_STALL this option
-   might be considered for Generic32 if our scheme for avoiding partial
-   stalls was more effective.  */
+
+/* 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_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_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_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)
+
 /* 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_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_ATOM | m_SLM 
           | m_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_ATOM | m_SLM | m_AMD_MULTIPLE 
           | m_GENERIC)
-/* X86_TUNE_SSE_PARTIAL_REG_DEPENDENCY: In the Generic model we have a
-   conflict here in between PPro/Pentium4 based chips that thread 128bit
-   SSE registers as single units versus K8 based chips that divide SSE
-   registers to two 64bit halves.  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.  */
+
+/* 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_ATOM | m_SLM | m_AMDFAM10 
           | m_BDVER | m_GENERIC)
+
+/* 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_COREI7 | m_AMDFAM10 | m_BDVER | m_BTVER | m_SLM | 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_COREI7 | m_BDVER | m_SLM | 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_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_SSE_TYPELESS_STORES: Always movaps/movups for 128bit stores. 
+   FIXME: Shall we enable it for generic?  */
 DEF_TUNE (X86_TUNE_SSE_TYPELESS_STORES, "sse_typeless_stores",
 	  m_AMD_MULTIPLE | m_CORE_ALL)
+
+/* X86_TUNE_SSE_LOAD0_BY_PXOR: Always use pxor to load0 as opposed to
+   xorps/xorpd and other variants.
+   FIXME: Shall we enable it buldozers and for generic?  */
 DEF_TUNE (X86_TUNE_SSE_LOAD0_BY_PXOR, "sse_load0_by_pxor",
 	  m_PPRO | m_P4_NOCONA | m_CORE_ALL)
+
+/* 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_ATOM | m_SLM | m_AMD_MULTIPLE | m_GENERIC)
+
+/* 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_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_USE_FFREEP: Use freep instruction instead of fstp.  */
 DEF_TUNE (X86_TUNE_USE_FFREEP, "use_ffreep", m_AMD_MULTIPLE)
+
+/* 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 ))
+          ~(m_AMDFAM10 | m_BDVER))
+
 /* 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_ATOM | m_SLM | m_ATHLON_K8 | m_AMDFAM10)
+
+/* X86_TUNE_SCHEDULE: Enable scheduling.  */
 DEF_TUNE (X86_TUNE_SCHEDULE, "schedule",
           m_PENT | m_PPRO | m_CORE_ALL | m_ATOM | m_SLM | m_K6_GEODE 
           | m_AMD_MULTIPLE | m_GENERIC)
+
+/* X86_TUNE_USE_BT: Enable use of BT (bit test) instructions.  */
 DEF_TUNE (X86_TUNE_USE_BT, "use_bt",
           m_CORE_ALL | m_ATOM | m_SLM | m_AMD_MULTIPLE | m_GENERIC)
+
+/* 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_ATOM | m_SLM | m_GENERIC))
+
+/* 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_PAD_SHORT_FUNCTION: Make every function to be at least 4
+   instructions long.  */
 DEF_TUNE (X86_TUNE_PAD_SHORT_FUNCTION, "pad_short_function", m_ATOM)
+
+/* 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_ATOM | m_SLM | m_K6_GEODE
           | m_ATHLON_K8 | m_GENERIC)
+
+/* 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_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_SLOW_IMUL_IMM32_MEM: Imul of 32-bit constant and memory is
-   vector path on AMD machines.  */
+   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_CORE_ALL | m_K8 | m_AMDFAM10 | m_BDVER | m_BTVER | m_GENERIC)
+
 /* X86_TUNE_SLOW_IMUL_IMM8: Imul of 8-bit constant is vector path on AMD
-   machines.  */
+   machines. 
+   FIXME: Do we need to enable this for core? */
 DEF_TUNE (X86_TUNE_SLOW_IMUL_IMM8, "slow_imul_imm8",
           m_CORE_ALL | m_K8 | m_AMDFAM10 | m_BDVER | m_BTVER | m_GENERIC)
+
 /* 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_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_USE_VECTOR_FP_CONVERTS: Prefer vector packed SSE conversion
-   from FP to FP. */
+   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_CORE_ALL | m_AMDFAM10 | m_GENERIC)
+
 /* 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_FUSE_CMP_AND_BRANCH: Fuse a compare or test instruction
    with a subsequent conditional jump instruction into a single
-   compare-and-branch uop.  */
+   compare-and-branch uop.
+   FIXME: revisit for generic.  */
 DEF_TUNE (X86_TUNE_FUSE_CMP_AND_BRANCH, "fuse_cmp_and_branch", m_BDVER | m_CORE_ALL)
+
 /* 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_ATOM | m_SLM)
+
 /* X86_TUNE_VECTORIZE_DOUBLE: Enable double precision vector
    instructions.  */
 DEF_TUNE (X86_TUNE_VECTORIZE_DOUBLE, "vectorize_double", ~m_ATOM)
+
 /* 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_AVX128_OPTIMAL: Enable 128-bit AVX instruction generation for
    the auto-vectorizer.  */
 DEF_TUNE (X86_TUNE_AVX128_OPTIMAL, "avx128_optimal", m_BDVER | m_BTVER2)
+
 /* 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_ATOM)
+
 /* 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_ATOM | m_SLM | m_HASWELL | m_BDVER1 | m_BDVER2 | m_GENERIC)
+
 /* 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_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_ATOM | m_SLM)
+
 /* 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",