From 5141ed426365a752343b2a8961d7b578f255b769 Mon Sep 17 00:00:00 2001 From: Jeff Law Date: Wed, 15 Apr 2015 06:24:28 -0600 Subject: [PATCH] re PR rtl-optimization/42522 ((zero_extract:SI (mem:QI) ...) misoptimized) PR rtl-optimization/42522 * cse.c (fold_rtx): Try to simplify a ZERO_EXTRACT or SIGN_EXTRACT as a whole object rather than simplifying its operand. From-SVN: r222125 --- gcc/ChangeLog | 7 +++++++ gcc/cse.c | 9 +++++++++ 2 files changed, 16 insertions(+) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index f1a96f270b5..a0f2fe7e2b9 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,10 @@ +2015-04-15 Jeff Law + + PR rtl-optimization/42522 + * cse.c (fold_rtx): Try to simplify a ZERO_EXTRACT or + SIGN_EXTRACT as a whole object rather than simplifying + its operand. + 2015-04-15 Jakub Jelinek PR ipa/65765 diff --git a/gcc/cse.c b/gcc/cse.c index 2a33827a61c..d7638f051f3 100644 --- a/gcc/cse.c +++ b/gcc/cse.c @@ -3150,6 +3150,15 @@ fold_rtx (rtx x, rtx_insn *insn) { case MEM: case SUBREG: + /* The first operand of a SIGN/ZERO_EXTRACT has a different meaning + than it would in other contexts. Basically its mode does not + signify the size of the object read. That information is carried + by size operand. If we happen to have a MEM of the appropriate + mode in our tables with a constant value we could simplify the + extraction incorrectly if we allowed substitution of that value + for the MEM. */ + case ZERO_EXTRACT: + case SIGN_EXTRACT: if ((new_rtx = equiv_constant (x)) != NULL_RTX) return new_rtx; return x;