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Round up the size of byval arguments to MinAlign

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Otherwise we can end up with an argument frame size that is not a
multiple of stack slot size, which is very awkward.

This fixes PR20547, which was a bug in x86_64 Sys V vararg handling.
However, it's much easier to test this with x86 callee-cleanup
functions, which previously ended in "retl $6" instead of "retl $8".

This does affect behavior of all backends, but it presumably fixes the
same bug in all of them.

llvm-svn: 214980
This commit is contained in:
Reid Kleckner 2014-08-06 17:57:23 +00:00
parent dcded783d2
commit e340c78d47
2 changed files with 29 additions and 0 deletions
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1
lib/CodeGen/CallingConvLower.cpp
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@ -52,6 +52,7 @@ void CCState::HandleByVal(unsigned ValNo, MVT ValVT,
Align = MinAlign;
MF.getFrameInfo()->ensureMaxAlignment(Align);
TM.getSubtargetImpl()->getTargetLowering()->HandleByVal(this, Size, Align);
Size = unsigned(RoundUpToAlignment(Size, MinAlign));
unsigned Offset = AllocateStack(Size, Align);
addLoc(CCValAssign::getMem(ValNo, ValVT, Offset, LocVT, LocInfo));
}

28
test/CodeGen/X86/byval-callee-cleanup.ll Normal file
View File

@ -0,0 +1,28 @@
; RUN: llc < %s -march=x86 | FileCheck %s
; Previously we would forget to align to stack slot alignment after placing a
; byval argument. Subsequent arguments would align themselves, but if it was
; the last argument, the argument size would not be a multiple of stack slot
; size. This resulted in retl $6 in callee-cleanup functions, as well as subtle
; varargs bugs.
%struct.Six = type { [6 x i8] }
define x86_stdcallcc void @f(%struct.Six* byval %a) {
ret void
}
; CHECK-LABEL: _f@8:
; CHECK: retl $8
define x86_thiscallcc void @g(i8* %this, %struct.Six* byval %a) {
ret void
}
; CHECK-LABEL: _g:
; CHECK: retl $8
define x86_fastcallcc void @h(i32 inreg %x, i32 inreg %y, %struct.Six* byval %a) {
ret void
}
; FIXME: This should be @h@8.
; CHECK-LABEL: @h@16:
; CHECK: retl $8