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[DAG] Fix the recognition of opaque constants in the SelectionDAGBuilder.

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This fix checks the original LLVM IR node to identify opaque constants by
looking for the bitcast-constant pattern. Originally we looked at the generated
SDNode, but this might lead to incorrect results. The SDNode could have been
generated by an constant expression that was folded to a constant.

This fixes <rdar://problem/16050719>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201291 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Juergen Ributzka 2014-02-13 04:19:26 +00:00
parent f79b906492
commit 525637575c
2 changed files with 20 additions and 3 deletions
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10
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
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@ -2996,9 +2996,13 @@ void SelectionDAGBuilder::visitBitCast(const User &I) {
if (DestVT != N.getValueType())
setValue(&I, DAG.getNode(ISD::BITCAST, getCurSDLoc(),
DestVT, N)); // convert types.
else if(ConstantSDNode *C = dyn_cast<ConstantSDNode>(N))
setValue(&I, DAG.getConstant(C->getAPIntValue(), C->getValueType(0),
/*isTarget=*/false, /*isOpaque*/true));
// Check if the original LLVM IR Operand was a ConstantInt, because getValue()
// might fold any kind of constant expression to an integer constant and that
// is not what we are looking for. Only regcognize a bitcast of a genuine
// constant integer as an opaque constant.
else if(ConstantInt *C = dyn_cast<ConstantInt>(I.getOperand(0)))
setValue(&I, DAG.getConstant(C->getValue(), DestVT, /*isTarget=*/false,
/*isOpaque*/true));
else
setValue(&I, N); // noop cast.
}

13
test/CodeGen/X86/opaque-constant-asm.ll Normal file
View File

@ -0,0 +1,13 @@
; RUN: llc < %s -mtriple=x86_64-apple-darwin | FileCheck %s
; This tests makes sure that we not mistake the bitcast inside the asm statement
; as an opaque constant. If we do, then the compilation will simply fail.
%struct2 = type <{ i32, i32, i32, i32 }>
%union.anon = type { [2 x i64], [4 x i32] }
%struct1 = type { i32, %union.anon }
define void @test() {
; CHECK: #ASM $16
call void asm sideeffect "#ASM $0", "n"(i32 ptrtoint (i32* getelementptr inbounds (%struct2* bitcast (%union.anon* getelementptr inbounds (%struct1* null, i32 0, i32 1) to %struct2*), i32 0, i32 2) to i32))
ret void
}