| Message ID | 20130306154732.GU12913@tucnak.redhat.com |
|---|---|
| State | New |
| Headers | show |
On 03/06/2013 07:47 AM, Jakub Jelinek wrote: > Hi! > > The http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=193539 > change broke the following testcase on i386. The problem is > that it can return the result in wider mode than callers expect, > causing either ICEs or other issues later on. > > It is fine to perform the cmove in promoted mode, but we should convert > it to the right mode at the end in order not to confuse callers. > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? > > 2013-03-06 Jakub Jelinek <jakub@redhat.com> > > PR middle-end/56548 > * expr.c (expand_cond_expr_using_cmove): When expanding cmove in > promoted mode, convert the result back to the original mode. > > * gcc.dg/pr56548.c: New test. Ok. r~
--- gcc/expr.c.jj 2013-02-25 20:29:52.000000000 +0100 +++ gcc/expr.c 2013-03-06 11:13:23.683387708 +0100 @@ -7884,6 +7884,7 @@ expand_cond_expr_using_cmove (tree treeo tree type = TREE_TYPE (treeop1); int unsignedp = TYPE_UNSIGNED (type); enum machine_mode mode = TYPE_MODE (type); + enum machine_mode orig_mode = mode; /* If we cannot do a conditional move on the mode, try doing it with the promoted mode. */ @@ -7949,7 +7950,7 @@ expand_cond_expr_using_cmove (tree treeo rtx seq = get_insns (); end_sequence (); emit_insn (seq); - return temp; + return convert_modes (orig_mode, mode, temp, 0); } /* Otherwise discard the sequence and fall back to code with --- gcc/testsuite/gcc.dg/pr56548.c.jj 2013-03-06 11:16:39.754325708 +0100 +++ gcc/testsuite/gcc.dg/pr56548.c 2013-03-06 11:16:12.000000000 +0100 @@ -0,0 +1,16 @@ +/* PR middle-end/56548 */ +/* { dg-do compile } */ +/* { dg-options "-O3" } */ +/* { dg-additional-options "-march=pentium3" { target { { i?86-*-* x86_64-*-* } && ia32 } } } */ + +short +foo (short x) +{ + int i; + + for (i = 0; i < 3; i++) + if (x > 0) + x--; + + return x; +}