diff options
Diffstat (limited to 'lib')
-rw-r--r-- | lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp | 16 | ||||
-rw-r--r-- | lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h | 2 | ||||
-rw-r--r-- | lib/CodeGen/SelectionDAG/TargetLowering.cpp | 26 |
3 files changed, 43 insertions, 1 deletions
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp index fc8f0d2..2a362eb 100644 --- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp +++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp @@ -2501,6 +2501,22 @@ void SelectionDAGBuilder::visitShift(const User &I, unsigned Opcode) { Op1.getValueType(), Op1, Op2)); } +void SelectionDAGBuilder::visitSDiv(const User &I) { + const BinaryOperator *BO = cast<BinaryOperator>(&I); + SDValue Op1 = getValue(I.getOperand(0)); + SDValue Op2 = getValue(I.getOperand(1)); + + // Turn exact SDivs into multiplications. + // FIXME: This should be in DAGCombiner, but it doesn't have access to the + // exact bit. + if (BO->isExact() && !isa<ConstantSDNode>(Op1) && + isa<ConstantSDNode>(Op2) && !cast<ConstantSDNode>(Op2)->isNullValue()) + setValue(&I, TLI.BuildExactSDIV(Op1, Op2, getCurDebugLoc(), DAG)); + else + setValue(&I, DAG.getNode(ISD::SDIV, getCurDebugLoc(), Op1.getValueType(), + Op1, Op2)); +} + void SelectionDAGBuilder::visitICmp(const User &I) { ICmpInst::Predicate predicate = ICmpInst::BAD_ICMP_PREDICATE; if (const ICmpInst *IC = dyn_cast<ICmpInst>(&I)) diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h index a1ca891..a0884eb 100644 --- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h +++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h @@ -467,7 +467,7 @@ private: void visitSRem(const User &I) { visitBinary(I, ISD::SREM); } void visitFRem(const User &I) { visitBinary(I, ISD::FREM); } void visitUDiv(const User &I) { visitBinary(I, ISD::UDIV); } - void visitSDiv(const User &I) { visitBinary(I, ISD::SDIV); } + void visitSDiv(const User &I); void visitFDiv(const User &I) { visitBinary(I, ISD::FDIV); } void visitAnd (const User &I) { visitBinary(I, ISD::AND); } void visitOr (const User &I) { visitBinary(I, ISD::OR); } diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp index 91e2a4a..f827f01 100644 --- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp +++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp @@ -3211,6 +3211,32 @@ bool TargetLowering::isLegalAddressingMode(const AddrMode &AM, return true; } +/// BuildExactDiv - Given an exact SDIV by a constant, create a multiplication +/// with the multiplicative inverse of the constant. +SDValue TargetLowering::BuildExactSDIV(SDValue Op1, SDValue Op2, DebugLoc dl, + SelectionDAG &DAG) const { + ConstantSDNode *C = cast<ConstantSDNode>(Op2); + APInt d = C->getAPIntValue(); + assert(d != 0 && "Division by zero!"); + + // Shift the value upfront if it is even, so the LSB is one. + unsigned ShAmt = d.countTrailingZeros(); + if (ShAmt) { + // TODO: For UDIV use SRL instead of SRA. + SDValue Amt = DAG.getConstant(ShAmt, getShiftAmountTy(Op1.getValueType())); + Op1 = DAG.getNode(ISD::SRA, dl, Op1.getValueType(), Op1, Amt); + d = d.ashr(ShAmt); + } + + // Calculate the multiplicative inverse, using Newton's method. + APInt t, xn = d; + while ((t = d*xn) != 1) + xn *= APInt(d.getBitWidth(), 2) - t; + + Op2 = DAG.getConstant(xn, Op1.getValueType()); + return DAG.getNode(ISD::MUL, dl, Op1.getValueType(), Op1, Op2); +} + /// BuildSDIVSequence - Given an ISD::SDIV node expressing a divide by constant, /// return a DAG expression to select that will generate the same value by /// multiplying by a magic number. See: |