[LLVMbugs] [Bug 15514] New: Incorrect calling convention at -O0 for x86_64-pc-win32 target

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=15514

            Bug ID: 15514
           Summary: Incorrect calling convention at -O0 for
                    x86_64-pc-win32 target
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows XP
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: jlerouge at apple.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

On the following IR:

target datalayout =
"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-pc-win32"

define i32 @foo(i32* %p) {
entry:
  %0 = load i32* %p, align 4
  ret i32 %0
}

define i32 @main(i32 %argc, i8** %argv) {
entry:
  %argc.addr = alloca i32, align 4
  store i32 %argc, i32* %argc.addr, align 4
  %call = call i32 @foo(i32* %argc.addr)
  ret i32 %call
}


llc -O0 produces this for foo:

    .def     foo;
    .scl    2;
    .type    32;
    .endef
    .text
    .globl    foo
    .align    16, 0x90
foo:                                    # @foo
# BB#0:                                 # %entry
    pushq    %rdi
    pushq    %rax
    movq    %rdi, (%rsp)
    movl    (%rdi), %eax
    addq    $8, %rsp
    popq    %rdi
    re

llc -O1 produces the correct output.

So, it looks like -O0 is using the wrong calling convention (argument should be
in %rcx, not %rdi). Since this only happens at -O0, it could be something in
X86FastISel.

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