//===--------------------------------------------------------------------===//
// Div utility functions
//
+ SDValue BuildExactSDIV(SDValue Op1, SDValue Op2, DebugLoc dl,
+ SelectionDAG &DAG) const;
SDValue BuildSDIV(SDNode *N, SelectionDAG &DAG,
std::vector<SDNode*>* Created) const;
SDValue BuildUDIV(SDNode *N, SelectionDAG &DAG,
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))
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); }
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:
--- /dev/null
+; RUN: llc -march=x86 < %s | FileCheck %s
+
+define i32 @test1(i32 %x) {
+ %div = sdiv exact i32 %x, 25
+ ret i32 %div
+; CHECK: test1:
+; CHECK: imull $-1030792151, 4(%esp)
+; CHECK-NEXT: ret
+}
+
+define i32 @test2(i32 %x) {
+ %div = sdiv exact i32 %x, 24
+ ret i32 %div
+; CHECK: test2:
+; CHECK: sarl $3
+; CHECK-NEXT: imull $-1431655765
+; CHECK-NEXT: ret
+}