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[CodeGen] Check FoldConstantArithmetic result before using it. 

Fixes PR24602: r245689 introduced an unguarded use of
SelectionDAG::FoldConstantArithmetic, which returns 0 when it fails
because of opaque (hoisted) constants.

llvm-svn: 246217
This commit is contained in:
Ahmed Bougacha 2015-08-27 21:46:04 +00:00
parent 8f5e331dc2
commit 87166905c8
2 changed files with 20 additions and 2 deletions
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5
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -4457,8 +4457,9 @@ SDValue DAGCombiner::visitSHL(SDNode *N) {
// fold (shl (mul x, c1), c2) -> (mul x, c1 << c2)
if (N1C && N0.getOpcode() == ISD::MUL && N0.getNode()->hasOneUse()) {
if (ConstantSDNode *N0C1 = isConstOrConstSplat(N0.getOperand(1))) {
SDValue Folded = DAG.FoldConstantArithmetic(ISD::SHL, SDLoc(N1), VT, N0C1, N1C);
return DAG.getNode(ISD::MUL, SDLoc(N), VT, N0.getOperand(0), Folded);
if (SDValue Folded =
DAG.FoldConstantArithmetic(ISD::SHL, SDLoc(N1), VT, N0C1, N1C))
return DAG.getNode(ISD::MUL, SDLoc(N), VT, N0.getOperand(0), Folded);
}
}

17
llvm/test/CodeGen/X86/pr24602.ll Normal file
View File

@ -0,0 +1,17 @@
; RUN: llc < %s -mtriple=x86_64-unknown-unknown | FileCheck %s
; PR24602: Make sure we don't barf on non-foldable code (with opaque constants).
; CHECK-LABEL: pr24602:
; CHECK-NEXT: # BB#0
; CHECK-NEXT: movabsq $-10000000000, [[CST:%[a-z0-9]+]]
; CHECK-NEXT: imulq [[CST]], %rsi
; CHECK-NEXT: leaq (%rdi,%rsi,8), %rax
; CHECK-NEXT: movq [[CST]], (%rdi,%rsi,8)
; CHECK-NEXT: retq
define i64* @pr24602(i64* %p, i64 %n) nounwind {
%mul = mul nsw i64 %n, -10000000000
%add.ptr = getelementptr inbounds i64, i64* %p, i64 %mul
store i64 -10000000000, i64* %add.ptr
ret i64* %add.ptr
}