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[Bug tree-optimization/31248] New: Too much casting for char operands on tree level
- From: "ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 17 Mar 2007 19:09:47 -0000
- Subject: [Bug tree-optimization/31248] New: Too much casting for char operands on tree level
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
Following testcase produces unnecessary moves in short loop:
--cut here--
char table[256];
int test(void) {
char val = 0;
int i;
for (i = 0; i < 10; i++)
val += table[i];
return val;
}
--cut here--
gcc -O2:
test:
.LFB2:
movzbl table(%rip), %ecx
movl $1, %edx
.p2align 4,,7
.L2:
(*) movl %ecx, %eax
addb table(%rdx), %al
addq $1, %rdx
cmpq $10, %rdx
(*) movl %eax, %ecx
jne .L2
movsbl %al,%eax
ret
Those unneccesary moves (*) are generated due to many (spurious?) casts in
optimized tree dump:
test ()
{
long unsigned int ivtmp.31;
char val;
unsigned char D.1985;
<bb 2>:
val = (char) (unsigned char) MEM[symbol: table];
ivtmp.31 = 1;
<L0>:;
D.1985 = (unsigned char) val + (unsigned char) MEM[symbol: table, index:
ivtmp.31];
val = (char) D.1985;
ivtmp.31 = ivtmp.31 + 1;
if (ivtmp.31 != 10) goto <L0>; else goto <L2>;
<L2>:;
return (int) val;
--
Summary: Too much casting for char operands on tree level
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: ubizjak at gmail dot com
GCC build triplet: x86_64-pc-linux-gnu
GCC host triplet: x86_64-pc-linux-gnu
GCC target triplet: x86_64-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31248