diff options
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 19 | ||||
| -rw-r--r-- | test/CodeGen/X86/shift-combine.ll | 1 |
2 files changed, 13 insertions, 7 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index ba3c0ac33d..fd0df3a0a1 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -2134,12 +2134,6 @@ SDOperand DAGCombiner::visitXOR(SDNode *N) { /// visitShiftByConstant - Handle transforms common to the three shifts, when /// the shift amount is a constant. SDOperand DAGCombiner::visitShiftByConstant(SDNode *N, unsigned Amt) { - // FIXME: disable this for now. This pessimizes some common cases like: - // - //void foo(int *X, int i) { X[i & 1235] = 1; } - //int bar(int *X, int i) { return X[i & 255]; } - return SDOperand(); - SDNode *LHS = N->getOperand(0).Val; if (!LHS->hasOneUse()) return SDOperand(); @@ -2169,6 +2163,19 @@ SDOperand DAGCombiner::visitShiftByConstant(SDNode *N, unsigned Amt) { ConstantSDNode *BinOpCst = dyn_cast<ConstantSDNode>(LHS->getOperand(1)); if (!BinOpCst) return SDOperand(); + + // FIXME: disable this for unless the input to the binop is a shift by a + // constant. If it is not a shift, it pessimizes some common cases like: + // + //void foo(int *X, int i) { X[i & 1235] = 1; } + //int bar(int *X, int i) { return X[i & 255]; } + SDNode *BinOpLHSVal = LHS->getOperand(0).Val; + if ((BinOpLHSVal->getOpcode() != ISD::SHL && + BinOpLHSVal->getOpcode() != ISD::SRA && + BinOpLHSVal->getOpcode() != ISD::SRL) || + !isa<ConstantSDNode>(BinOpLHSVal->getOperand(1))) + return SDOperand(); + MVT::ValueType VT = N->getValueType(0); // If this is a signed shift right, and the high bit is modified diff --git a/test/CodeGen/X86/shift-combine.ll b/test/CodeGen/X86/shift-combine.ll index c8df5b0208..543bb22378 100644 --- a/test/CodeGen/X86/shift-combine.ll +++ b/test/CodeGen/X86/shift-combine.ll @@ -1,5 +1,4 @@ ; RUN: llvm-as < %s | llc | not grep shrl -; XFAIL: * target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128" target triple = "i686-apple-darwin8" |