http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50603
--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> 2011-10-06 19:00:54 UTC --- [hjl@gnu-mic-2 pr50633]$ cat x.i struct s { int val[16]; }; extern double f (struct s pb, double pc); int main () { struct s x; int i; for (i = 0; i < 16; i++) x.val[i] = i + 1; if (f (x, 10000.0L) != 10136.0L) __builtin_abort (); return 0; } [hjl@gnu-mic-2 pr50633]$ make x.s /export/build/gnu/gcc-x32/build-x86_64-linux/gcc/xgcc -B/export/build/gnu/gcc-x32/build-x86_64-linux/gcc/ -mx32 -O -S x.i [hjl@gnu-mic-2 pr50633]$ cat x.s .file "x.i" .text .globl main .type main, @function main: .LFB0: .cfi_startproc subq $136, %rsp .cfi_def_cfa_offset 144 movl $0, %eax movl %esp, %ecx addl $60, %ecx .L2: addl $1, %eax leal (%rcx,%rax,4), %edx movl %eax, (%edx) cmpl $16, %eax jne .L2 movq 64(%rsp), %rax movq %rax, (%rsp) movq 72(%rsp), %rax movq %rax, 8(%rsp) movq 80(%rsp), %rax movq %rax, 16(%rsp) movq 88(%rsp), %rax movq %rax, 24(%rsp) movq 96(%rsp), %rax movq %rax, 32(%rsp) movq 104(%rsp), %rax movq %rax, 40(%rsp) movq 112(%rsp), %rax movq %rax, 48(%rsp) movq 120(%rsp), %rax movq %rax, 56(%rsp) movsd .LC0(%rip), %xmm0 call f ucomisd .LC1(%rip), %xmm0 jp .L5 je .L7 .L5: call abort .L7: movl $0, %eax addq $136, %rsp .cfi_def_cfa_offset 8 ret .cfi_endproc .LFE0: .size main, .-main leal (%rcx,%rax,4), %edx movl %eax, (%edx) can be combined into movl %eax, (%ecx,%eax,4)