diff options
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 31 | ||||
| -rw-r--r-- | test/CodeGen/X86/shift-pair.ll | 11 |
2 files changed, 27 insertions, 15 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index d219c58112..e843f5fa34 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -3092,26 +3092,27 @@ SDValue DAGCombiner::visitSHL(SDNode *N) { } } - // fold (shl (srl x, c1), c2) -> (shl (and x, (shl -1, c1)), (sub c2, c1)) or - // (srl (and x, (shl -1, c1)), (sub c1, c2)) + // fold (shl (srl x, c1), c2) -> (and (shl x, (sub c2, c1), MASK) or + // (and (srl x, (sub c1, c2), MASK) if (N1C && N0.getOpcode() == ISD::SRL && N0.getOperand(1).getOpcode() == ISD::Constant) { uint64_t c1 = cast<ConstantSDNode>(N0.getOperand(1))->getZExtValue(); if (c1 < VT.getSizeInBits()) { uint64_t c2 = N1C->getZExtValue(); - SDValue HiBitsMask = - DAG.getConstant(APInt::getHighBitsSet(VT.getSizeInBits(), - VT.getSizeInBits() - c1), - VT); - SDValue Mask = DAG.getNode(ISD::AND, N0.getDebugLoc(), VT, - N0.getOperand(0), - HiBitsMask); - if (c2 > c1) - return DAG.getNode(ISD::SHL, N->getDebugLoc(), VT, Mask, - DAG.getConstant(c2-c1, N1.getValueType())); - else - return DAG.getNode(ISD::SRL, N->getDebugLoc(), VT, Mask, - DAG.getConstant(c1-c2, N1.getValueType())); + APInt Mask = APInt::getHighBitsSet(VT.getSizeInBits(), + VT.getSizeInBits() - c1); + SDValue Shift; + if (c2 > c1) { + Mask = Mask.shl(c2-c1); + Shift = DAG.getNode(ISD::SHL, N->getDebugLoc(), VT, N0.getOperand(0), + DAG.getConstant(c2-c1, N1.getValueType())); + } else { + Mask = Mask.lshr(c1-c2); + Shift = DAG.getNode(ISD::SRL, N->getDebugLoc(), VT, N0.getOperand(0), + DAG.getConstant(c1-c2, N1.getValueType())); + } + return DAG.getNode(ISD::AND, N0.getDebugLoc(), VT, Shift, + DAG.getConstant(Mask, VT)); } } // fold (shl (sra x, c1), c1) -> (and x, (shl -1, c1)) diff --git a/test/CodeGen/X86/shift-pair.ll b/test/CodeGen/X86/shift-pair.ll new file mode 100644 index 0000000000..24ba1fc770 --- /dev/null +++ b/test/CodeGen/X86/shift-pair.ll @@ -0,0 +1,11 @@ +; RUN: llc < %s -march=x86-64 | FileCheck %s + +define i64 @test(i64 %A) { +; CHECK: @test +; CHECK: shrq $54 +; CHECK: andq $1020 +; CHECK: ret + %B = lshr i64 %A, 56 + %C = shl i64 %B, 2 + ret i64 %C +} |