diff options
| -rw-r--r-- | lib/Transforms/Utils/SimplifyCFG.cpp | 27 | ||||
| -rw-r--r-- | test/Transforms/SimplifyCFG/SpeculativeExec.ll | 29 |
2 files changed, 9 insertions, 47 deletions
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index 9f3464d..11cb25d 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -1369,8 +1369,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) { /// \endcode /// /// \returns true if the conditional block is removed. -static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB, - const TargetTransformInfo &TTI) { +static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB) { // Be conservative for now. FP select instruction can often be expensive. Value *BrCond = BI->getCondition(); if (isa<FCmpInst>(BrCond)) @@ -1399,22 +1398,15 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB, // Only speculatively execution a single instruction (not counting the // terminator) for now. - SpeculationCost += TTI.getUserCost(I); - if (SpeculationCost > TargetTransformInfo::TCC_Basic) + ++SpeculationCost; + if (SpeculationCost > 1) return false; // Don't hoist the instruction if it's unsafe or expensive. if (!isSafeToSpeculativelyExecute(I)) return false; - // FIXME: This should really be a cost metric, but our cost model doesn't - // accurately model the expense of select. - if (isa<SelectInst>(I)) + if (ComputeSpeculationCost(I) > PHINodeFoldingThreshold) return false; - // FIXME: The cost metric currently doesn't reason accurately about simple - // versus complex GEPs, take a conservative approach here. - if (GEPOperator *GEP = dyn_cast<GEPOperator>(I)) - if (!GEP->hasAllConstantIndices()) - return false; // Do not hoist the instruction if any of its operands are defined but not // used in this BB. The transformation will prevent the operand from @@ -1457,10 +1449,9 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB, // Account for the cost of an unfolded ConstantExpr which could end up // getting expanded into Instructions. // FIXME: This doesn't account for how many operations are combined in the - // constant expression. The cost functions in TTI don't yet correctly model - // constant expression costs. - SpeculationCost += TargetTransformInfo::TCC_Basic; - if (SpeculationCost > TargetTransformInfo::TCC_Basic) + // constant expression. + ++SpeculationCost; + if (SpeculationCost > 1) return false; } @@ -3877,7 +3868,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { TerminatorInst *Succ0TI = BI->getSuccessor(0)->getTerminator(); if (Succ0TI->getNumSuccessors() == 1 && Succ0TI->getSuccessor(0) == BI->getSuccessor(1)) - if (SpeculativelyExecuteBB(BI, BI->getSuccessor(0), TTI)) + if (SpeculativelyExecuteBB(BI, BI->getSuccessor(0))) return SimplifyCFG(BB, TTI, TD) | true; } } else if (BI->getSuccessor(1)->getSinglePredecessor() != 0) { @@ -3886,7 +3877,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { TerminatorInst *Succ1TI = BI->getSuccessor(1)->getTerminator(); if (Succ1TI->getNumSuccessors() == 1 && Succ1TI->getSuccessor(0) == BI->getSuccessor(0)) - if (SpeculativelyExecuteBB(BI, BI->getSuccessor(1), TTI)) + if (SpeculativelyExecuteBB(BI, BI->getSuccessor(1))) return SimplifyCFG(BB, TTI, TD) | true; } diff --git a/test/Transforms/SimplifyCFG/SpeculativeExec.ll b/test/Transforms/SimplifyCFG/SpeculativeExec.ll index bcef848..7e27f41 100644 --- a/test/Transforms/SimplifyCFG/SpeculativeExec.ll +++ b/test/Transforms/SimplifyCFG/SpeculativeExec.ll @@ -108,32 +108,3 @@ end: ret i8* %x10 } - -define i16 @test5(i1* %dummy, i16 %a, i16 %b) { -; Test that we speculate no-op instructions. -; CHECK: @test5 - -entry: - %cond1 = load volatile i1* %dummy - br i1 %cond1, label %if, label %end - -if: - %cond2 = load volatile i1* %dummy - %a.conv = sext i16 %a to i32 - %b.conv = sext i16 %b to i32 - %cmp = icmp ult i32 %a.conv, %b.conv - br i1 %cond2, label %then, label %end - -then: - %sub = sub i32 %a.conv, %b.conv - %sub.conv = trunc i32 %sub to i16 - br label %end - -end: - %x = phi i16 [ %a, %entry ], [ %b, %if ], [ %sub.conv, %then ] -; CHECK-NOT: phi -; CHECK: select i1 - - ret i16 %x -} - |