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