[Win64] incorrect stack frame with alloca(n) and call

[llvmbot]

Bugzilla Link	8778
Resolution	FIXED
Resolved on	Mar 28, 2011 00:25
Version	trunk
OS	Windows XP
Blocks	llvm/llvm-bugzilla-archive#9100
Reporter	LLVM Bugzilla Contributor

Extended Description

define i64 @​foo(i64 %n) nounwind {
entry:
%buf = alloca i8, i64 %n, align 1
%r = call i64 @​bar(i8* %buf, i64 %n, i64 %n, i64 %n, i64 %n) nounwind
ret i64 %r
}
declare i64 @​bar(i8* nocapture, i64, i64, i64, i64) nounwind

$ llc -mtriple=x86_64-win32
foo:
pushq %rbp
movq %rsp, %rbp
subq $32, %rsp
movq %rcx, %rdx
leaq 15(%rdx), %rax
andq $-16, %rax
movq %rsp, %rcx
subq %rax, %rcx ;;; @​bar: 1st arg
movq %rcx, %rsp
subq $16, %rsp ;;; 40 (or aligned 48) bytes would be needed
movq %rdx, 32(%rsp) ;;; it might be on %buf
movq %rdx, %r8
movq %rdx, %r9
callq bar ;;; 32 bytes home area overlaps to %buf
movq %rbp, %rsp
popq %rbp
ret

Even when @​bar() has args less than 4, stack frame would be incorrect.

[llvmbot]

Fixed in r124949. (chkstk issue is pending)

foo:
pushq %rbp
movq %rsp, %rbp
movq %rcx, %rdx
leaq 15(%rdx), %rax
andq $-16, %rax
movq %rsp, %rcx
subq %rax, %rcx
movq %rcx, %rsp
subq $48, %rsp
movq %rdx, 32(%rsp)
movq %rdx, %r8
movq %rdx, %r9
callq bar
movq %rbp, %rsp
popq %rbp
ret

[llvmbot]

___chkstk is now emitted in r128206.

[llvmbot]

mentioned in issue llvm/llvm-bugzilla-archive#9100