diff options
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 11 | ||||
| -rw-r--r-- | test/CodeGen/X86/pr14562.ll | 15 |
2 files changed, 24 insertions, 2 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 5b83149982..67fa39d9c2 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -5163,8 +5163,15 @@ SDValue DAGCombiner::ReduceLoadWidth(SDNode *N) { EVT ShImmTy = getShiftAmountTy(Result.getValueType()); if (!isUIntN(ShImmTy.getSizeInBits(), ShLeftAmt)) ShImmTy = VT; - Result = DAG.getNode(ISD::SHL, N0.getDebugLoc(), VT, - Result, DAG.getConstant(ShLeftAmt, ShImmTy)); + // If the shift amount is as large as the result size (but, presumably, + // no larger than the source) then the useful bits of the result are + // zero; we can't simply return the shortened shift, because the result + // of that operation is undefined. + if (ShLeftAmt >= VT.getSizeInBits()) + Result = DAG.getConstant(0, VT); + else + Result = DAG.getNode(ISD::SHL, N0.getDebugLoc(), VT, + Result, DAG.getConstant(ShLeftAmt, ShImmTy)); } // Return the new loaded value. diff --git a/test/CodeGen/X86/pr14562.ll b/test/CodeGen/X86/pr14562.ll new file mode 100644 index 0000000000..2df64b301d --- /dev/null +++ b/test/CodeGen/X86/pr14562.ll @@ -0,0 +1,15 @@ +; RUN: llc < %s -march=x86 | FileCheck %s + +@temp1 = global i64 -77129852189294865, align 8 + +define void @foo() nounwind { + %x = load i64* @temp1, align 8 + %s = shl i64 %x, 32 + %t = trunc i64 %s to i32 + %z = zext i32 %t to i64 + store i64 %z, i64* @temp1, align 8 +; CHECK: movl $0, temp1+4 +; CHECK: movl $0, temp1 + ret void +} + |