diff options
Diffstat (limited to 'lib/Transforms/Scalar/IndVarSimplify.cpp')
| -rw-r--r-- | lib/Transforms/Scalar/IndVarSimplify.cpp | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp index 97fff7e782..8e76c78f5a 100644 --- a/lib/Transforms/Scalar/IndVarSimplify.cpp +++ b/lib/Transforms/Scalar/IndVarSimplify.cpp @@ -535,6 +535,45 @@ void IndVarSimplify::RewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter) { if (!SE->isLoopInvariant(ExitValue, L)) continue; + // Computing the value outside of the loop brings no benefit if : + // - it is definitely used inside the loop in a way which can not be + // optimized away. + // - no use outside of the loop can take advantage of hoisting the + // computation out of the loop + if (ExitValue->getSCEVType()>=scMulExpr) { + unsigned NumHardInternalUses = 0; + unsigned NumSoftExternalUses = 0; + unsigned NumUses = 0; + for (Value::use_iterator IB=Inst->use_begin(), IE=Inst->use_end(); + IB!=IE && NumUses<=6 ; ++IB) { + Instruction *UseInstr = cast<Instruction>(*IB); + unsigned Opc = UseInstr->getOpcode(); + NumUses++; + if (L->contains(UseInstr)) { + if (Opc == Instruction::Call || Opc == Instruction::Ret) + NumHardInternalUses++; + } else { + if (Opc == Instruction::PHI) { + // Do not count the Phi as a use. LCSSA may have inserted + // plenty of trivial ones. + NumUses--; + for (Value::use_iterator PB=UseInstr->use_begin(), + PE=UseInstr->use_end(); + PB!=PE && NumUses<=6 ; ++PB, ++NumUses) { + unsigned PhiOpc = cast<Instruction>(*PB)->getOpcode(); + if (PhiOpc != Instruction::Call && PhiOpc != Instruction::Ret) + NumSoftExternalUses++; + } + continue; + } + if (Opc != Instruction::Call && Opc != Instruction::Ret) + NumSoftExternalUses++; + } + } + if (NumUses <= 6 && NumHardInternalUses && !NumSoftExternalUses) + continue; + } + Value *ExitVal = Rewriter.expandCodeFor(ExitValue, PN->getType(), Inst); DEBUG(dbgs() << "INDVARS: RLEV: AfterLoopVal = " << *ExitVal << '\n' |