Leaf functions that don't use the frame set up a frame anyway

[llvmbot]

Bugzilla Link	9121
Resolution	FIXED
Resolved on	Feb 02, 2011 00:43
Version	trunk
OS	Linux
Reporter	LLVM Bugzilla Contributor
CC	@lattner,@nlewycky

Extended Description

For example:

test.cc:
#include
long foo(std::vector&v) {
return v.size();
}

g++-4.6svn -S test.cc -o - -O2 -m32:
_Z3fooRSt6vectorIiSaIiEE:
.LFB442:
movl 4(%esp), %edx
movl 4(%edx), %eax
subl (%edx), %eax
sarl $2, %eax
ret

g++-4.6svn -S test.cc -o - -O2 -m64:
_Z3fooRSt6vectorIiSaIiEE:
.LFB442:
movq 8(%rdi), %rax
subq (%rdi), %rax
sarq $2, %rax
ret

clang++ -S test.cc -o - -O2 -m32
_Z3fooRSt6vectorIiSaIiEE: # @​_Z3fooRSt6vectorIiSaIiEE

BB#0: # %entry

    pushl   %ebp
    movl    %esp, %ebp
    movl    8(%ebp), %ecx
    movl    4(%ecx), %eax
    subl    (%ecx), %eax
    sarl    $2, %eax
    popl    %ebp
    ret

clang++ -S test.cc -o - -O2 -m64:
_Z3fooRSt6vectorIiSaIiEE: # @​_Z3fooRSt6vectorIiSaIiEE
.Leh_func_begin0:

BB#0: # %entry

    pushq   %rbp

.Ltmp0:
movq %rsp, %rbp
.Ltmp1:
movq 8(%rdi), %rax
subq (%rdi), %rax
sarq $2, %rax
popq %rbp
ret

[lattner]

Does -momit-leaf-frame-pointer get what you want? It sounds like GCC defaults that to on for linux, but noone has taught clang that yet.

[nlewycky]

Thanks Chris! Fixed in r124718.