https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82682
--- Comment #2 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
We now generate:
.L3:
movzbl (%edx), %esi
addl $2, %edx
addl $1, %ecx
movzbl -1(%edx), %eax
movl %esi, %ebx
imull $38470, %eax, %eax
movzbl %bl, %esi
imull $19595, %esi, %esi
addl %esi, %eax
sarl $16, %eax
movb %al, -1(%ecx)
cmpl %edi, %edx
jne .L3
while from older gcc I get
.L3:
movzbl (%ecx,%edx,2), %eax
movzbl 1(%ecx,%edx,2), %edi
imull $19595, %eax, %eax
imull $38470, %edi, %edi
addl %edi, %eax
sarl $16, %eax
movb %al, (%esi,%edx)
addl $1, %edx
cmpl %edx, %ebx
jne .L3
.L1:
There is clearly missed optimization on movzbl $bl, esi because it is already
extended.
I wonder how this can be triggered by the move cost changes, perhaps regalloc
difference?
Jakub, it is easy for you to get .s files from r253958 and just before?
