[Bug tree-optimization/67607] New: Failure to perform constant folding through type conversion
miyuki at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Thu Sep 17 07:46:00 GMT 2015
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67607
Bug ID: 67607
Summary: Failure to perform constant folding through type
conversion
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: miyuki at gcc dot gnu.org
Target Milestone: ---
This code is taken from PR67606:
$ cat pr67606.c
int f(int a[], int length)
{
int count=0;
for (int i = 0 ; i < length ; i++)
if (a[i] > 5)
count++;
return count;
}
$ g++ -S -O3 -fno-tree-vectorize pr67606.c -fverbose-asm -fdump-tree-optimized
We get:
<bb 3>:
ivtmp.6_1 = (unsigned long) a_7(D);
_19 = (unsigned int) length_4(D);
_18 = _19 + 4294967295;
_21 = (sizetype) _18;
_22 = _21 + 1;
_23 = _22 * 4;
_24 = a_7(D) + _23;
_25 = (unsigned long) _24;
And this leads to generating some redundant code:
leal -1(%rsi), %eax #, tmp114
leaq 4(%rdi,%rax,4), %rcx #, tmp111
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