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| author | Torok Edwin <edwintorok@gmail.com> | 2008-10-24 19:20:05 +0000 |
|---|---|---|
| committer | Torok Edwin <edwintorok@gmail.com> | 2008-10-24 19:20:05 +0000 |
| commit | db1b3bc2763b5c28742b913984cfe600a3917f62 (patch) | |
| tree | 97e6b95cbd4454f23b6e7f13b1d151a19ef261e6 /lib/Target/README.txt | |
| parent | 56ab0def902940d6eee7b8eb668f974e78f3dcbb (diff) | |
| download | llvm-db1b3bc2763b5c28742b913984cfe600a3917f62.tar.gz llvm-db1b3bc2763b5c28742b913984cfe600a3917f62.tar.bz2 llvm-db1b3bc2763b5c28742b913984cfe600a3917f62.tar.xz | |
add note about va_arg code on x86 and x86-64
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58103 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Target/README.txt')
| -rw-r--r-- | lib/Target/README.txt | 94 |
1 files changed, 94 insertions, 0 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index 9ff4b5b337..b3018b21dd 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -985,3 +985,97 @@ define i1 @test(i8 %x) { //===---------------------------------------------------------------------===// +This code: + +int foo(const char *str,...) +{ + __builtin_va_list a; int x; + __builtin_va_start(a,str); x = __builtin_va_arg(a,int); __builtin_va_end(a); + return x; +} + +gets compiled into this on x86-64: + subq $200, %rsp + movaps %xmm7, 160(%rsp) + movaps %xmm6, 144(%rsp) + movaps %xmm5, 128(%rsp) + movaps %xmm4, 112(%rsp) + movaps %xmm3, 96(%rsp) + movaps %xmm2, 80(%rsp) + movaps %xmm1, 64(%rsp) + movaps %xmm0, 48(%rsp) + movq %r9, 40(%rsp) + movq %r8, 32(%rsp) + movq %rcx, 24(%rsp) + movq %rdx, 16(%rsp) + movq %rsi, 8(%rsp) + leaq (%rsp), %rax + movq %rax, 192(%rsp) + leaq 208(%rsp), %rax + movq %rax, 184(%rsp) + movl $48, 180(%rsp) + movl $8, 176(%rsp) + movl 176(%rsp), %eax + cmpl $47, %eax + jbe .LBB1_3 # bb +.LBB1_1: # bb3 + movq 184(%rsp), %rcx + leaq 8(%rcx), %rax + movq %rax, 184(%rsp) +.LBB1_2: # bb4 + movl (%rcx), %eax + addq $200, %rsp + ret +.LBB1_3: # bb + movl %eax, %ecx + addl $8, %eax + addq 192(%rsp), %rcx + movl %eax, 176(%rsp) + jmp .LBB1_2 # bb4 + +gcc 4.3 generates: + subq $96, %rsp +.LCFI0: + leaq 104(%rsp), %rax + movq %rsi, -80(%rsp) + movl $8, -120(%rsp) + movq %rax, -112(%rsp) + leaq -88(%rsp), %rax + movq %rax, -104(%rsp) + movl $8, %eax + cmpl $48, %eax + jb .L6 + movq -112(%rsp), %rdx + movl (%rdx), %eax + addq $96, %rsp + ret + .p2align 4,,10 + .p2align 3 +.L6: + mov %eax, %edx + addq -104(%rsp), %rdx + addl $8, %eax + movl %eax, -120(%rsp) + movl (%rdx), %eax + addq $96, %rsp + ret + +and it gets compiled into this on x86: + pushl %ebp + movl %esp, %ebp + subl $4, %esp + leal 12(%ebp), %eax + movl %eax, -4(%ebp) + leal 16(%ebp), %eax + movl %eax, -4(%ebp) + movl 12(%ebp), %eax + addl $4, %esp + popl %ebp + ret + +gcc 4.3 generates: + pushl %ebp + movl %esp, %ebp + movl 12(%ebp), %eax + popl %ebp + ret |