From 84682fd249b3f86e88e79b47527b168c873dc5f0 Mon Sep 17 00:00:00 2001 From: Richard Earnshaw Date: Fri, 30 Jun 2017 16:36:57 +0000 Subject: [PATCH] [rtlanal] Do a better job of costing parallel sets containing flag-setting operations. Many parallel set insns are of the form of a single set that also sets the condition code flags. In this case the cost of such an insn is normally the cost of the part that doesn't set the flags, since updating the condition flags is simply a side effect. At present all such insns are treated as having unknown cost (ie 0) and combine assumes that such insns are infinitely more expensive than any other insn sequence with a non-zero cost. This patch addresses this problem by allowing insn_rtx_cost to ignore the condition setting part of a PARALLEL iff there is exactly one comparison set and one non-comparison set. If the only set operation is a comparison we still use that as the basis of the insn cost. * rtlanal.c (insn_rtx_cost): If a parallel contains exactly one comparison set and one other set, use the cost of the non-comparison set. Bootstrapped on aarch64-none-linuxgnu From-SVN: r249850 --- gcc/ChangeLog | 6 ++++++ gcc/rtlanal.c | 28 +++++++++++++++++++++++----- 2 files changed, 29 insertions(+), 5 deletions(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 594b2472eaa..e0a9cc009aa 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2017-06-30 Richard Earnshaw + + * rtlanal.c (insn_rtx_cost): If a parallel contains exactly one + comparison set and one other set, use the cost of the non-comparison + set. + 2017-06-30 Nathan Sidwell * ggc.h: Replace all 'static inline' with plain 'inline'. Fix diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c index bf4183e793d..9bfae8cb9b0 100644 --- a/gcc/rtlanal.c +++ b/gcc/rtlanal.c @@ -5263,23 +5263,41 @@ insn_rtx_cost (rtx pat, bool speed) int i, cost; rtx set; - /* Extract the single set rtx from the instruction pattern. - We can't use single_set since we only have the pattern. */ + /* Extract the single set rtx from the instruction pattern. We + can't use single_set since we only have the pattern. We also + consider PARALLELs of a normal set and a single comparison. In + that case we use the cost of the non-comparison SET operation, + which is most-likely to be the real cost of this operation. */ if (GET_CODE (pat) == SET) set = pat; else if (GET_CODE (pat) == PARALLEL) { set = NULL_RTX; + rtx comparison = NULL_RTX; + for (i = 0; i < XVECLEN (pat, 0); i++) { rtx x = XVECEXP (pat, 0, i); if (GET_CODE (x) == SET) { - if (set) - return 0; - set = x; + if (GET_CODE (SET_SRC (x)) == COMPARE) + { + if (comparison) + return 0; + comparison = x; + } + else + { + if (set) + return 0; + set = x; + } } } + + if (!set && comparison) + set = comparison; + if (!set) return 0; } -- 2.30.2