From 4a01617886c1833f456948048e5167dac784ef19 Mon Sep 17 00:00:00 2001 From: Segher Boessenkool Date: Wed, 29 Nov 2017 23:42:37 +0100 Subject: [PATCH] combine: Do not throw away unneeded arms of parallels (PR83156) The fix for PR82621 makes us not split an I2 if one of the results of those SETs is unused, since combine does not handle that properly. But this results in degradation for i386 (or more in general, for any target that does not have patterns for parallels with an unused result as a CLOBBER instead of a SET for that result). This patch instead makes us not split only if one of the results is set again before I3. That fixes PR83156 and also fixes PR82621. Unfortunately it undoes the nice optimisations that the previous patch did on powerpc. PR rtl-optimization/83156 PR rtl-optimization/82621 * combine.c (try_combine): Don't split an I2 if one of the dests is set again before I3. Allow unused dests. From-SVN: r255260 --- gcc/ChangeLog | 7 +++++++ gcc/combine.c | 3 ++- 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 62ca3dca421..c13f67e76a6 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,10 @@ +2017-11-29 Segher Boessenkool + + PR rtl-optimization/83156 + PR rtl-optimization/82621 + * combine.c (try_combine): Don't split an I2 if one of the dests is + set again before I3. Allow unused dests. + 2017-11-29 Segher Boessenkool * config/rs6000/rs6000.md (*add3_carry_in_internal2): New. diff --git a/gcc/combine.c b/gcc/combine.c index 0ce07511a3e..cfe24f42633 100644 --- a/gcc/combine.c +++ b/gcc/combine.c @@ -3016,7 +3016,8 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0, && can_split_parallel_of_n_reg_sets (i2, 2) && !reg_used_between_p (SET_DEST (XVECEXP (PATTERN (i2), 0, 0)), i2, i3) && !reg_used_between_p (SET_DEST (XVECEXP (PATTERN (i2), 0, 1)), i2, i3) - && !find_reg_note (i2, REG_UNUSED, 0)) + && !reg_set_between_p (SET_DEST (XVECEXP (PATTERN (i2), 0, 0)), i2, i3) + && !reg_set_between_p (SET_DEST (XVECEXP (PATTERN (i2), 0, 1)), i2, i3)) { /* If there is no I1, there is no I0 either. */ i0 = i1; -- 2.30.2