gcc (GCC) 4.4.0 20090109 (experimental) [trunk revision 143212]
On x86_64-unknown-linux-gnu (FC9)
Configured as: ../trunk/configure --prefix=/home/ddaney/gccsvn/native-install
--disable-multilib --enable-languages=c
Consider the following program:
---foo.c--------8<----------------
void bar(int v)
{
unsigned a;
a = (v == 1) ? 1 : 2;
if (__builtin_constant_p(a)) {
asm volatile ("you lose. %0" : : "ir" (a));
} else {
asm volatile ("you win. %0" : : "ir" (a));
}
}
--------------8<----------------
$ gcc -O2 -S foo.c
$ cat foo.s
.file "foo.c"
.text
.p2align 4,,15
.globl bar
.type bar, @function
bar:
.LFB0:
.cfi_startproc
xorl %eax, %eax
cmpl $1, %edi
setne %al
addl $1, %eax
#APP
# 9 "foo.c" 1
you lose. %eax
# 0 "" 2
#NO_APP
ret
.cfi_endproc
.LFE0:
.size bar, .-bar
.ident "GCC: (GNU) 4.4.0 20090109 (experimental) [trunk revision
143212]"
.section .note.GNU-stack,"",@progbits
It emits the asm from the __builtin_constant_p branch of the if statement.
Initial analysis points to VRP as being the problem.
For the system gcc (gcc (GCC) 4.3.0 20080428 (Red Hat 4.3.0-8)) it work
correctly.
--
Summary: __builtin_constant_p appears to eveluate to true for
non-constant arguments.
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: daney at gcc dot gnu dot org
GCC build triplet: x86_64-unknown-linux-gnu
GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-unknown-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38789
