http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47953
Summary: Code generation depends on function prototype Product: gcc Version: 4.6.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassig...@gcc.gnu.org ReportedBy: hjl.to...@gmail.com CC: js...@gcc.gnu.org On Linux/x86-64, I got [hjl@gnu-6 ilp32-27]$ cat x.c void (*foo[6][6]) (int); void bar (hdR) int hdR; { } void xxx () { unsigned int i, j; for (i = 0; i < 6; ++i) for (j = 0; j < 6; ++j) foo [i][j] = bar; } [hjl@gnu-6 ilp32-27]$ cat y.c void (*foo[6][6]) (int); void bar (int hdR) { } void xxx () { unsigned int i, j; for (i = 0; i < 6; ++i) for (j = 0; j < 6; ++j) foo [i][j] = bar; } [hjl@gnu-6 ilp32-27]$ make x.s y.s /export/build/gnu/gcc-x32/build-x86_64-linux/gcc/xgcc -B/export/build/gnu/gcc-x32/build-x86_64-linux/gcc/ -S -o x.s -O3 x.c /export/build/gnu/gcc-x32/build-x86_64-linux/gcc/xgcc -B/export/build/gnu/gcc-x32/build-x86_64-linux/gcc/ -S -o y.s -O3 y.c [hjl@gnu-6 ilp32-27]$ cat x.s y.s .file "x.c" .text .p2align 4,,15 .globl bar .type bar, @function bar: .LFB0: .cfi_startproc rep ret .cfi_endproc .LFE0: .size bar, .-bar .p2align 4,,15 .globl xxx .type xxx, @function xxx: .LFB1: .cfi_startproc movq .LC0(%rip), %xmm1 punpcklqdq %xmm1, %xmm1 movdqa %xmm1, foo(%rip) movdqa %xmm1, foo+16(%rip) movdqa %xmm1, foo+32(%rip) movdqa %xmm1, foo+48(%rip) movdqa %xmm1, foo+64(%rip) movdqa %xmm1, foo+80(%rip) movdqa %xmm1, foo+96(%rip) movdqa %xmm1, foo+112(%rip) movdqa %xmm1, foo+128(%rip) movdqa %xmm1, foo+144(%rip) movdqa %xmm1, foo+160(%rip) movdqa %xmm1, foo+176(%rip) movdqa %xmm1, foo+192(%rip) movdqa %xmm1, foo+208(%rip) movdqa %xmm1, foo+224(%rip) movdqa %xmm1, foo+240(%rip) movdqa %xmm1, foo+256(%rip) movdqa %xmm1, foo+272(%rip) ret .cfi_endproc .LFE1: .size xxx, .-xxx .comm foo,288,32 .section .rodata.cst8,"aM",@progbits,8 .align 8 .LC0: .quad bar .ident "GCC: (GNU) 4.6.0 20110224 (experimental)" .section .note.GNU-stack,"",@progbits .file "y.c" .text .p2align 4,,15 .globl bar .type bar, @function bar: .LFB0: .cfi_startproc rep ret .cfi_endproc .LFE0: .size bar, .-bar .p2align 4,,15 .globl xxx .type xxx, @function xxx: .LFB1: .cfi_startproc movq $bar, foo(%rip) movq $bar, foo+8(%rip) movq $bar, foo+16(%rip) movq $bar, foo+24(%rip) movq $bar, foo+32(%rip) movq $bar, foo+40(%rip) movq $bar, foo+48(%rip) movq $bar, foo+56(%rip) movq $bar, foo+64(%rip) movq $bar, foo+72(%rip) movq $bar, foo+80(%rip) movq $bar, foo+88(%rip) movq $bar, foo+96(%rip) movq $bar, foo+104(%rip) movq $bar, foo+112(%rip) movq $bar, foo+120(%rip) movq $bar, foo+128(%rip) movq $bar, foo+136(%rip) movq $bar, foo+144(%rip) movq $bar, foo+152(%rip) movq $bar, foo+160(%rip) movq $bar, foo+168(%rip) movq $bar, foo+176(%rip) movq $bar, foo+184(%rip) movq $bar, foo+192(%rip) movq $bar, foo+200(%rip) movq $bar, foo+208(%rip) movq $bar, foo+216(%rip) movq $bar, foo+224(%rip) movq $bar, foo+232(%rip) movq $bar, foo+240(%rip) movq $bar, foo+248(%rip) movq $bar, foo+256(%rip) movq $bar, foo+264(%rip) movq $bar, foo+272(%rip) movq $bar, foo+280(%rip) ret .cfi_endproc .LFE1: .size xxx, .-xxx .comm foo,288,32 .ident "GCC: (GNU) 4.6.0 20110224 (experimental)" .section .note.GNU-stack,"",@progbits [hjl@gnu-6 ilp32-27]$ The only difference in input is: void bar (hdR) int hdR; { } vs. void bar (int hdR) { } I am expecting the same assembly code.