/// isFormingBranchFromSelectProfitable - Returns true if a SelectInst should be
/// turned into an explicit branch.
static bool isFormingBranchFromSelectProfitable(SelectInst *SI) {
// FIXME: This should use the same heuristics as IfConversion to determine
// whether a select is better represented as a branch. This requires that
// branch probability metadata is preserved for the select, which is not the
// case currently.
CmpInst *Cmp = dyn_cast<CmpInst>(SI->getCondition());
// If the branch is predicted right, an out of order CPU can avoid blocking on
// the compare. Emit cmovs on compares with a memory operand as branches to
// avoid stalls on the load from memory. If the compare has more than one use
// there's probably another cmov or setcc around so it's not worth emitting a
// branch.
if (!Cmp)
return false;
Value *CmpOp0 = Cmp->getOperand(0);
Value *CmpOp1 = Cmp->getOperand(1);
// We check that the memory operand has one use to avoid uses of the loaded
// value directly after the compare, making branches unprofitable.
return Cmp->hasOneUse() &&
((isa<LoadInst>(CmpOp0) && CmpOp0->hasOneUse()) ||
(isa<LoadInst>(CmpOp1) && CmpOp1->hasOneUse()));
}
/// Returns true if the select instruction has users in the compare-and-add
/// reduction pattern below. The select instruction argument is the last one
/// in the sequence.
///
/// %sum.1 = phi ...
/// ...
/// %cmp = fcmp pred %0, %CFP
/// %add = fadd %0, %sum.1
/// %sum.2 = select %cmp, %add, %sum.1
RecurrenceDescriptor::InstDesc
RecurrenceDescriptor::isConditionalRdxPattern(
RecurrenceKind Kind, Instruction *I) {
SelectInst *SI = dyn_cast<SelectInst>(I);
if (!SI)
return InstDesc(false, I);
CmpInst *CI = dyn_cast<CmpInst>(SI->getCondition());
// Only handle single use cases for now.
if (!CI || !CI->hasOneUse())
return InstDesc(false, I);
Value *TrueVal = SI->getTrueValue();
Value *FalseVal = SI->getFalseValue();
// Handle only when either of operands of select instruction is a PHI
// node for now.
if ((isa<PHINode>(*TrueVal) && isa<PHINode>(*FalseVal)) ||
(!isa<PHINode>(*TrueVal) && !isa<PHINode>(*FalseVal)))
return InstDesc(false, I);
Instruction *I1 =
isa<PHINode>(*TrueVal) ? dyn_cast<Instruction>(FalseVal)
: dyn_cast<Instruction>(TrueVal);
if (!I1 || !I1->isBinaryOp())
return InstDesc(false, I);
Value *Op1, *Op2;
if ((m_FAdd(m_Value(Op1), m_Value(Op2)).match(I1) ||
m_FSub(m_Value(Op1), m_Value(Op2)).match(I1)) &&
I1->isFast())
return InstDesc(Kind == RK_FloatAdd, SI);
if (m_FMul(m_Value(Op1), m_Value(Op2)).match(I1) && (I1->isFast()))
return InstDesc(Kind == RK_FloatMult, SI);
return InstDesc(false, I);
}