On 21 May 2014 20:43, Steven Bosscher <stevenb....@gmail.com> wrote: > On Wed, May 21, 2014 at 11:58 AM, Zhenqiang Chen wrote: >> Hi, >> >> The patch fixes the gcc.target/i386/pr49095.c FAIL in PR61225. The >> test case tends to check a peephole2 optimization, which optimizes the >> following sequence >> >> 2: bx:SI=ax:SI >> 25: ax:SI=[bx:SI] >> 7: {ax:SI=ax:SI-0x1;clobber flags:CC;} >> 8: [bx:SI]=ax:SI >> 9: flags:CCZ=cmp(ax:SI,0) >> to >> 2: bx:SI=ax:SI >> 41: {flags:CCZ=cmp([bx:SI]-0x1,0);[bx:SI]=[bx:SI]-0x1;} >> >> The enhanced shrink-wrapping, which calls copyprop_hardreg_forward >> changes the INSN 25 to >> >> 25: ax:SI=[ax:SI] >> >> Then peephole2 can not optimize it since two memory_operands look like >> different. >> >> To fix it, the patch adds another peephole2 rule to read one more >> insn. From the register copy, it knows the address is the same. > > That is one complex peephole2 to deal with a transformation like this. > It seems to be like it's a too specific solution for a bigger problem. > > Could you please try one of the following solutions instead: > > 1. Track register values for peephole2 and try different alternatives > based on known register equivalences? E.g. in your example, perhaps > there is already a REG_EQUAL/REG_EQUIV note available on insn 25 after > copyprop_hardreg_forward, to annotate that [ax:SI] is equivalent to > [bx:SI] at that point (or if that information is not available, it is > not very difficult to make it available). Then you could try applying > peephole2 on the original pattern but also on patterns modified with > the known equivalences (i.e. try peephole2 on multiple equivalent > patterns for the same insn). This may expose other peephole2 > opportunities, not just the specific one your patch addresses.
Patch is updated according to the comment. There is no REG_EQUAL. So I add it when replace_oldest_value_reg. ChangeLog: 2014-05-22 Zhenqiang Chen <zhenqiang.c...@linaro.org> Part of PR rtl-optimization/61225 * config/i386/i386-protos.h (ix86_peephole2_rtx_equal_p): New proto. * config/i386/i386.c (ix86_peephole2_rtx_equal_p): New function. * regcprop.c (replace_oldest_value_reg): Add REG_EQUAL note when propagating to SET. diff --git a/gcc/config/i386/i386-protos.h b/gcc/config/i386/i386-protos.h index 39462bd..0c4a2b9 100644 --- a/gcc/config/i386/i386-protos.h +++ b/gcc/config/i386/i386-protos.h @@ -42,6 +42,7 @@ extern enum calling_abi ix86_function_type_abi (const_tree); extern void ix86_reset_previous_fndecl (void); +extern bool ix86_peephole2_rtx_equal_p (rtx, rtx, rtx, rtx); #ifdef RTX_CODE extern int standard_80387_constant_p (rtx); extern const char *standard_80387_constant_opcode (rtx); diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c index 6ffb788..583ebe8 100644 --- a/gcc/config/i386/i386.c +++ b/gcc/config/i386/i386.c @@ -46856,6 +46856,29 @@ ix86_atomic_assign_expand_fenv (tree *hold, tree *clear, tree *update) atomic_feraiseexcept_call); } +/* OP0 is the SET_DEST of INSN and OP1 is the SET_SRC of INSN. + Check whether OP1 and OP6 is equal. */ + +bool +ix86_peephole2_rtx_equal_p (rtx insn, rtx op0, rtx op1, rtx op6) +{ + rtx note; + + if (!reg_overlap_mentioned_p (op0, op1) && rtx_equal_p (op1, op6)) + return true; + + gcc_assert (single_set (insn) + && op0 == SET_DEST (single_set (insn)) + && op1 == SET_SRC (single_set (insn))); + + note = find_reg_note (insn, REG_EQUAL, NULL_RTX); + if (note + && !reg_overlap_mentioned_p (op0, XEXP (note, 0)) + && rtx_equal_p (XEXP (note, 0), op6)) + return true; + + return false; +} /* Initialize the GCC target structure. */ #undef TARGET_RETURN_IN_MEMORY #define TARGET_RETURN_IN_MEMORY ix86_return_in_memory diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md index 44e80ec..b57fc86 100644 --- a/gcc/config/i386/i386.md +++ b/gcc/config/i386/i386.md @@ -16996,11 +16996,12 @@ [(match_dup 0) (match_operand:SWI 2 "<nonmemory_operand>")])) (clobber (reg:CC FLAGS_REG))]) - (set (match_dup 1) (match_dup 0)) + (set (match_operand:SWI 6 "memory_operand") (match_dup 0)) (set (reg FLAGS_REG) (compare (match_dup 0) (const_int 0)))] "(TARGET_READ_MODIFY_WRITE || optimize_insn_for_size_p ()) && peep2_reg_dead_p (4, operands[0]) - && !reg_overlap_mentioned_p (operands[0], operands[1]) + && ix86_peephole2_rtx_equal_p (peep2_next_insn (0), operands[0], + operands[1], operands[6]) && !reg_overlap_mentioned_p (operands[0], operands[2]) && (<MODE>mode != QImode || immediate_operand (operands[2], QImode) diff --git a/gcc/regcprop.c b/gcc/regcprop.c index 7a5a4f6..4e09724 100644 --- a/gcc/regcprop.c +++ b/gcc/regcprop.c @@ -510,6 +510,22 @@ replace_oldest_value_reg (rtx *loc, enum reg_class cl, rtx insn, fprintf (dump_file, "insn %u: replaced reg %u with %u\n", INSN_UID (insn), REGNO (*loc), REGNO (new_rtx)); + if (single_set (insn) && GET_CODE (PATTERN (insn)) == SET + && GET_MODE_CLASS (GET_MODE (SET_DEST (insn))) != MODE_CC + && GET_CODE (SET_SRC (single_set (insn))) != COMPARE) + { + rtx set = single_set (insn); + rtx dest = SET_DEST (set); + + if (REG_P (dest) && REG_P (new_rtx) + && REGNO (dest) == REGNO (new_rtx)) + /* REGNO of the NEW_RTX is modified by INSN. No way to forwarded + it any more. So add REG_EQUAL note to record its previous + value. This note can be used to check whether two RTXs + equal or not. */ + add_reg_note (insn, REG_EQUAL, copy_rtx (SET_SRC (set))); + } + validate_change (insn, loc, new_rtx, 1); return true; }