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Re-revert r173342, without losing the compile time improvements, flat
out bug fixes, or functionality preserving refactorings. llvm-svn: 173610
This commit is contained in:
Chandler Carruth
parent
307107e1ea
commit
ce01d44307
@ -1369,8 +1369,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
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/// \endcode
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///
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/// \returns true if the conditional block is removed.
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static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB,
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const TargetTransformInfo &TTI) {
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static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB) {
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// Be conservative for now. FP select instruction can often be expensive.
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Value *BrCond = BI->getCondition();
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if (isa<FCmpInst>(BrCond))
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@ -1406,24 +1405,15 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB,
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// Only speculatively execution a single instruction (not counting the
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// terminator) for now.
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SpeculationCost += TTI.getUserCost(I);
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if (SpeculationCost > TargetTransformInfo::TCC_Basic)
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++SpeculationCost;
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if (SpeculationCost > 1)
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return false;
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// Don't hoist the instruction if it's unsafe or expensive.
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if (!isSafeToSpeculativelyExecute(I))
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return false;
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// FIXME: These should really be cost metrics, but our cost model doesn't
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// accurately model the expense of selects and floating point operations.
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// FIXME: Is it really safe to speculate floating point operations?
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// Signaling NaNs break with this, but we shouldn't care, right?
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if (isa<SelectInst>(I) || I->getType()->isFPOrFPVectorTy())
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if (ComputeSpeculationCost(I) > PHINodeFoldingThreshold)
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return false;
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// FIXME: The cost metric currently doesn't reason accurately about simple
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// versus complex GEPs, take a conservative approach here.
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if (GEPOperator *GEP = dyn_cast<GEPOperator>(I))
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if (!GEP->hasAllConstantIndices())
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return false;
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// Do not hoist the instruction if any of its operands are defined but not
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// used in this BB. The transformation will prevent the operand from
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@ -1446,8 +1436,8 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB,
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SinkCandidateUseCounts.begin(), E = SinkCandidateUseCounts.end();
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I != E; ++I)
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if (I->first->getNumUses() == I->second) {
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SpeculationCost += TTI.getUserCost(I->first);
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if (SpeculationCost > TargetTransformInfo::TCC_Basic)
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++SpeculationCost;
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if (SpeculationCost > 1)
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return false;
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}
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@ -1469,20 +1459,15 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB,
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if (!isSafeToSpeculativelyExecute(CE))
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return false;
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// Don't speculate into a select with a constant select expression operand.
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// FIXME: This should really be a cost metric, but our cost model doesn't
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// accurately model the expense of select.
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if (Operator::getOpcode(CE) == Instruction::Select)
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if (ComputeSpeculationCost(CE) > PHINodeFoldingThreshold)
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return false;
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// Account for the cost of an unfolded ConstantExpr which could end up
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// getting expanded into Instructions.
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// FIXME: This doesn't account for how many operations are combined in the
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// constant expression. The cost functions in TTI don't yet correctly model
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// constant expression costs.
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SpeculationCost += TargetTransformInfo::TCC_Basic;
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if (SpeculationCost > TargetTransformInfo::TCC_Basic)
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// constant expression.
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++SpeculationCost;
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if (SpeculationCost > 1)
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return false;
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}
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@ -3899,7 +3884,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
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TerminatorInst *Succ0TI = BI->getSuccessor(0)->getTerminator();
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if (Succ0TI->getNumSuccessors() == 1 &&
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Succ0TI->getSuccessor(0) == BI->getSuccessor(1))
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if (SpeculativelyExecuteBB(BI, BI->getSuccessor(0), TTI))
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if (SpeculativelyExecuteBB(BI, BI->getSuccessor(0)))
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return SimplifyCFG(BB, TTI, TD) | true;
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}
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} else if (BI->getSuccessor(1)->getSinglePredecessor() != 0) {
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@ -3908,7 +3893,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
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TerminatorInst *Succ1TI = BI->getSuccessor(1)->getTerminator();
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if (Succ1TI->getNumSuccessors() == 1 &&
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Succ1TI->getSuccessor(0) == BI->getSuccessor(0))
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if (SpeculativelyExecuteBB(BI, BI->getSuccessor(1), TTI))
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if (SpeculativelyExecuteBB(BI, BI->getSuccessor(1)))
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return SimplifyCFG(BB, TTI, TD) | true;
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}
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@ -44,29 +44,6 @@ join:
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ret i8 %c
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}
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define i8* @test3(i1* %dummy, i8* %a, i8* %b) {
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; Test that a weird, unfolded constant cast in the PHI don't block speculation.
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; CHECK: @test3
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entry:
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%cond1 = load volatile i1* %dummy
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br i1 %cond1, label %if, label %end
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if:
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%cond2 = load volatile i1* %dummy
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br i1 %cond2, label %then, label %end
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then:
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br label %end
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end:
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%x = phi i8* [ %a, %entry ], [ %b, %if ], [ inttoptr (i64 42 to i8*), %then ]
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; CHECK-NOT: phi
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; CHECK: select i1 %cond2, i8* inttoptr
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ret i8* %x
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}
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define i8* @test4(i1* %dummy, i8* %a, i8* %b) {
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; Test that we don't speculate an arbitrarily large number of unfolded constant
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; expressions.
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@ -108,95 +85,3 @@ end:
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ret i8* %x10
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}
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define i16 @test5(i1* %dummy, i16 %a, i16 %b) {
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; Test that we speculate no-op instructions.
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; CHECK: @test5
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entry:
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%cond1 = load volatile i1* %dummy
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br i1 %cond1, label %if, label %end
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if:
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%cond2 = load volatile i1* %dummy
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%a.conv = sext i16 %a to i32
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%b.conv = sext i16 %b to i32
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%cmp = icmp ult i32 %a.conv, %b.conv
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br i1 %cond2, label %then, label %end
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then:
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%sub = sub i32 %a.conv, %b.conv
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%sub.conv = trunc i32 %sub to i16
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br label %end
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end:
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%x = phi i16 [ %a, %entry ], [ %b, %if ], [ %sub.conv, %then ]
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; CHECK-NOT: phi
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; CHECK: select i1
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ret i16 %x
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}
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define i16 @test6(i1* %dummy, i64 %a, i64 %b) {
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; Test that we speculate no-op instructions when those instructions are in the
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; predecessor but could potentially be sunk.
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; CHECK: @test6
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entry:
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%cond1 = load volatile i1* %dummy
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%a.conv = trunc i64 %a to i16
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%b.conv = trunc i64 %b to i16
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br i1 %cond1, label %if, label %end
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if:
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%cond2 = load volatile i1* %dummy
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%cond3 = load volatile i1* %dummy
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%cond4 = load volatile i1* %dummy
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%cmp = icmp ult i16 %a.conv, %b.conv
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%a.conv2 = trunc i64 %a to i32
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%b.conv2 = trunc i64 %b to i32
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br i1 %cond2, label %then, label %end
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then:
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%sub = sub i32 %a.conv2, %b.conv2
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%sub.conv = trunc i32 %sub to i16
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br label %end
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end:
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%x = phi i16 [ %a.conv, %entry ], [ %b.conv, %if ], [ %sub.conv, %then ]
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; CHECK-NOT: phi
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; CHECK: select i1
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ret i16 %x
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}
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define i16 @test7(i1* %dummy, i16 %a, i16 %b, i32 %x) {
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; Test that we don't speculate when there are instructions that could
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; potentially sink into the conditional block.
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; CHECK: @test7
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entry:
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%cond1 = load volatile i1* %dummy
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br i1 %cond1, label %if, label %end
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if:
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%cond2 = load volatile i1* %dummy
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%a.conv = sext i16 %a to i32
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%b.conv = sext i16 %b to i32
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%cmp = icmp ult i32 %a.conv, %b.conv
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%a.conv2 = add i32 %a.conv, %x
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br i1 %cond2, label %then, label %end
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then:
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%sub = sub i32 %a.conv2, %b.conv
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%sub.conv = trunc i32 %sub to i16
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br label %end
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end:
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%y = phi i16 [ %a, %entry ], [ %b, %if ], [ %sub.conv, %then ]
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; CHECK-NOT: select
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; CHECK: phi i16
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ret i16 %y
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}
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