| Summary: | non-needed instructions are not removed (not optimized) | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Коренберг Марк <socketpair> |
| Component: | middle-end | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | RESOLVED FIXED | ||
| Severity: | minor | CC: | gcc-bugs |
| Priority: | P3 | ||
| Version: | 4.3.3 | ||
| Target Milestone: | 4.4.0 | ||
| Host: | Target: | ||
| Build: | Known to work: | 4.4.0 | |
| Known to fail: | 4.3.4 4.3.3 | Last reconfirmed: | |
gcc322 generates this:
(gcc -Os -fomit-frame-pointer qwe.c --save-temps)
main:
movl $1, %eax
ret
WTF?
It aligns the incoming stack. Fixed in 4.4/4.5. |
int main (void) { return 1; } Ubuntu Jaunty. gcc --save-temps -fno-stack-protector -fomit-frame-pointer -Os ./cpuid.c generates thgis: -------------- main: leal 4(%esp), %ecx andl $-16, %esp pushl -4(%ecx) movl $1, %eax pushl %ecx popl %ecx leal -4(%ecx), %esp ret -------------------------- why i get this: pushl %ecx popl %ecx and other non-needed instructions (for another example) pushl %ebp andl $1, %eax movl %esp, %ebp pushl %ecx popl %ecx popl %ebp These instructions are not optimized not in -O3, nor in -Os