[llvm] r216119 - X86: Align the stack on word boundaries in LowerFormalArguments()

[Reid Kleckner]

How was this not handled by r214980?


On Wed, Aug 20, 2014 at 12:40 PM, Duncan P. N. Exon Smith <
dexonsmith at apple.com> wrote:

> Author: dexonsmith
> Date: Wed Aug 20 14:40:59 2014
> New Revision: 216119
>
> URL: http://llvm.org/viewvc/llvm-project?rev=216119&view=rev
> Log:
> X86: Align the stack on word boundaries in LowerFormalArguments()
>
> The goal of the patch is to implement section 3.2.3 of the AMD64 ABI
> correctly.  The controlling sentence is, "The size of each argument gets
> rounded up to eightbytes.  Therefore the stack will always be eightbyte
> aligned." The equivalent sentence in the i386 ABI page 37 says, "At all
> times, the stack pointer should point to a word-aligned area."  For both
> architectures, the stack pointer is not being rounded up to the nearest
> eightbyte or word between the last normal argument and the first
> variadic argument.
>
> Patch by Thomas Jablin!
>
> Added:
>     llvm/trunk/test/CodeGen/X86/aligned-variadic.ll
> Modified:
>     llvm/trunk/include/llvm/CodeGen/CallingConvLower.h
>     llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
>
> Modified: llvm/trunk/include/llvm/CodeGen/CallingConvLower.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/CallingConvLower.h?rev=216119&r1=216118&r2=216119&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/CodeGen/CallingConvLower.h (original)
> +++ llvm/trunk/include/llvm/CodeGen/CallingConvLower.h Wed Aug 20 14:40:59
> 2014
> @@ -371,11 +371,16 @@ public:
>      return Reg;
>    }
>
> +  /// AlignStack - Align the top of the stakc to the specified alignment.
> +  void AlignStack(unsigned Align) {
> +    assert(Align && ((Align - 1) & Align) == 0); // Align is power of 2.
> +    StackOffset = ((StackOffset + Align - 1) & ~(Align - 1));
> +  }
> +
>    /// AllocateStack - Allocate a chunk of stack space with the specified
> size
>    /// and alignment.
>    unsigned AllocateStack(unsigned Size, unsigned Align) {
> -    assert(Align && ((Align-1) & Align) == 0); // Align is power of 2.
> -    StackOffset = ((StackOffset + Align-1) & ~(Align-1));
> +    AlignStack(Align);
>      unsigned Result = StackOffset;
>      StackOffset += Size;
>      MF.getFrameInfo()->ensureMaxAlignment(Align);
>
> Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=216119&r1=216118&r2=216119&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
> +++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Wed Aug 20 14:40:59 2014
> @@ -2300,6 +2300,7 @@ X86TargetLowering::LowerFormalArguments(
>      CCInfo.AllocateStack(32, 8);
>
>    CCInfo.AnalyzeFormalArguments(Ins, CC_X86);
> +  CCInfo.AlignStack(Is64Bit ? 8 : 4);
>
>    unsigned LastVal = ~0U;
>    SDValue ArgValue;
>
> Added: llvm/trunk/test/CodeGen/X86/aligned-variadic.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/aligned-variadic.ll?rev=216119&view=auto
>
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/aligned-variadic.ll (added)
> +++ llvm/trunk/test/CodeGen/X86/aligned-variadic.ll Wed Aug 20 14:40:59
> 2014
> @@ -0,0 +1,30 @@
> +; RUN: llc < %s -march=x86-64 | FileCheck %s -check-prefix=X64
> +; RUN: llc < %s -march=x86    | FileCheck %s -check-prefix=X32
> +
> +%struct.Baz = type { [17 x i8] }
> +%struct.__va_list_tag = type { i32, i32, i8*, i8* }
> +
> +; Function Attrs: nounwind uwtable
> +define void @bar(%struct.Baz* byval nocapture readnone align 8 %x, ...) {
> +entry:
> +  %va = alloca [1 x %struct.__va_list_tag], align 16
> +  %arraydecay = getelementptr inbounds [1 x %struct.__va_list_tag]* %va,
> i64 0, i64 0
> +  %arraydecay1 = bitcast [1 x %struct.__va_list_tag]* %va to i8*
> +  call void @llvm.va_start(i8* %arraydecay1)
> +  %overflow_arg_area_p = getelementptr inbounds [1 x
> %struct.__va_list_tag]* %va, i64 0, i64 0, i32 2
> +  %overflow_arg_area = load i8** %overflow_arg_area_p, align 8
> +  %overflow_arg_area.next = getelementptr i8* %overflow_arg_area, i64 24
> +  store i8* %overflow_arg_area.next, i8** %overflow_arg_area_p, align 8
> +; X32: leal    68(%esp), [[REG:%.*]]
> +; X32: movl    [[REG]], 16(%esp)
> +; X64: leaq    232(%rsp), [[REG:%.*]]
> +; X64: movq    [[REG]], 184(%rsp)
> +; X64: leaq    176(%rsp), %rdi
> +  call void @qux(%struct.__va_list_tag* %arraydecay)
> +  ret void
> +}
> +
> +; Function Attrs: nounwind
> +declare void @llvm.va_start(i8*)
> +
> +declare void @qux(%struct.__va_list_tag*)
>
>
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