------- Comment #3 from jakub at gcc dot gnu dot org 2008-11-07 16:19 -------
In assembly, it seems the a and b arguments to mymemcmp1 aren't stored into
memory at all:
.loc 1 128 0
movq (%rax), %r12 #* srcp2.272, b0
.LVL54:
.loc 1 126 0
movq (%rdi), %rsi #* srcp1, a3
.LVL55:
.loc 1 127 0
movq 8(%rdi), %rbx #, a0
.LVL56:
.loc 1 129 0
addq $8, %rdi #, srcp1.270
.LVL57:
.L28:
.loc 1 152 0
movl %r9d, %ecx #,
.LVL58:
movq %rbx, %r10 # a0, tmp154
.loc 1 149 0
movq 8(%rdi), %r11 #, a1
.LVL59:
.loc 1 152 0
salq %cl, %r10 #, tmp154
movl %r8d, %ecx #,
.loc 1 150 0
movq 8(%rax), %rbp #, b1
.LVL60:
.loc 1 152 0
shrq %cl, %rsi #, tmp155
.LVL61:
orq %rsi, %r10 # tmp155, tmp156
cmpq %r12, %r10 # b0, tmp156
je .L26 #,
.LBB112:
.LBB113:
.loc 1 8 0
leaq -8(%rsp), %rcx #, srcp1
.LVL62:
.loc 1 9 0
leaq -16(%rsp), %rdx #, srcp2
.LVL63:
.p2align 4,,10
.p2align 3
.L31:
.loc 1 13 0
movzbl (%rcx), %eax #* srcp1, a0
.LVL64:
.loc 1 14 0
movzbl (%rdx), %edi #* srcp2, b0
...
At je .L26 insn %r12 register contains correct value of b0 variable and %r10 of
x (shifted + ored together value). But then suddenly the code assumes it is in
memory without actually storing it there.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38051
