http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59036
Bug ID: 59036
Summary: [4.9 regression] Performance degradation after r204212
on 32-bit x86 targets.
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: ysrumyan at gmail dot com
After patch to improve register preferencing in IRA and to *remove regmove*
pass we noticed performance degradation on several benchmarks from eembc2.0
suite in 32-bit mode for all x86 targets (such as atom, slm, hsw, etc.).
This can be reproduced with attached test-case - after fix 3 more instructions
are generated for innermost loop (compiled with -O2 -m32 -march=core-avx2
options):
before fix
.L4:
movl 12(%esp), %edx
addl $3, %ecx
movl 4(%esp), %ebx
movl (%esp), %ebp
movl 8(%esp), %esi
movzbl (%edx,%eax), %edi
movl 16(%esp), %edx
movzbl (%ebx,%eax), %ebx
movzbl (%esi,%eax), %esi
addl $1, %eax
addl (%edx,%edi,4), %ebp
movzbl 0(%ebp,%ebx), %edx
movl 28(%esp), %ebp
movb %dl, -3(%ecx)
movl 24(%esp), %edx
movl (%edx,%edi,4), %edx
movl (%esp), %edi
addl 0(%ebp,%esi,4), %edx
leal (%edi,%ebx), %ebp
sarl $16, %edx
movzbl 0(%ebp,%edx), %edx
movl 20(%esp), %ebp
movb %dl, -2(%ecx)
movl 0(%ebp,%esi,4), %edx
addl %edi, %edx
movzbl (%edx,%ebx), %edx
movb %dl, -1(%ecx)
cmpl 80(%esp), %eax
jne .L4
after fix
.L4:
movl 8(%esp), %ebx
addl $3, %edx
movl 12(%esp), %esi
movl 4(%esp), %ecx
movzbl (%ebx,%eax), %ebx
movzbl (%esi,%eax), %esi
movzbl (%ecx,%eax), %ecx
addl $1, %eax
movb %bl, (%esp)
movl 16(%esp), %ebx
movl (%ebx,%esi,4), %ebp
addl %edi, %ebp
movzbl 0(%ebp,%ecx), %ebx
movzbl (%esp), %ebp
movb %bl, -3(%edx)
movl 24(%esp), %ebx
movl %ebp, (%esp)
movl (%ebx,%esi,4), %esi
movl 28(%esp), %ebx
addl (%ebx,%ebp,4), %esi
leal (%edi,%ecx), %ebp
sarl $16, %esi
movzbl 0(%ebp,%esi), %ebx
movl 20(%esp), %esi
movl (%esp), %ebp
movb %bl, -2(%edx)
movl %edi, %ebx
addl (%esi,%ebp,4), %ebx
movzbl (%ebx,%ecx), %ecx
movb %cl, -1(%edx)
cmpl 80(%esp), %eax
jne .L4
