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-rw-r--r--lib/Transforms/Utils/SimplifyCFG.cpp39
-rw-r--r--test/Transforms/SimplifyCFG/SpeculativeExec.ll115
2 files changed, 12 insertions, 142 deletions
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 3cf39843dd..a63d31d5af 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))
@@ -1406,24 +1405,15 @@ 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: These should really be cost metrics, but our cost model doesn't
- // accurately model the expense of selects and floating point operations.
- // FIXME: Is it really safe to speculate floating point operations?
- // Signaling NaNs break with this, but we shouldn't care, right?
- if (isa<SelectInst>(I) || I->getType()->isFPOrFPVectorTy())
+ 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
@@ -1446,8 +1436,8 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB,
SinkCandidateUseCounts.begin(), E = SinkCandidateUseCounts.end();
I != E; ++I)
if (I->first->getNumUses() == I->second) {
- SpeculationCost += TTI.getUserCost(I->first);
- if (SpeculationCost > TargetTransformInfo::TCC_Basic)
+ ++SpeculationCost;
+ if (SpeculationCost > 1)
return false;
}
@@ -1469,20 +1459,15 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB,
if (!isSafeToSpeculativelyExecute(CE))
return false;
-
- // Don't speculate into a select with a constant select expression operand.
- // FIXME: This should really be a cost metric, but our cost model doesn't
- // accurately model the expense of select.
- if (Operator::getOpcode(CE) == Instruction::Select)
+ if (ComputeSpeculationCost(CE) > PHINodeFoldingThreshold)
return false;
// 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;
}
@@ -3899,7 +3884,7 @@ 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) {
@@ -3908,7 +3893,7 @@ 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 b60e5dc56f..dd2e5d1c3a 100644
--- a/test/Transforms/SimplifyCFG/SpeculativeExec.ll
+++ b/test/Transforms/SimplifyCFG/SpeculativeExec.ll
@@ -44,29 +44,6 @@ join:
ret i8 %c
}
-define i8* @test3(i1* %dummy, i8* %a, i8* %b) {
-; Test that a weird, unfolded constant cast in the PHI don't block speculation.
-; CHECK: @test3
-
-entry:
- %cond1 = load volatile i1* %dummy
- br i1 %cond1, label %if, label %end
-
-if:
- %cond2 = load volatile i1* %dummy
- br i1 %cond2, label %then, label %end
-
-then:
- br label %end
-
-end:
- %x = phi i8* [ %a, %entry ], [ %b, %if ], [ inttoptr (i64 42 to i8*), %then ]
-; CHECK-NOT: phi
-; CHECK: select i1 %cond2, i8* inttoptr
-
- ret i8* %x
-}
-
define i8* @test4(i1* %dummy, i8* %a, i8* %b) {
; Test that we don't speculate an arbitrarily large number of unfolded constant
; expressions.
@@ -108,95 +85,3 @@ 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
-}
-
-define i16 @test6(i1* %dummy, i64 %a, i64 %b) {
-; Test that we speculate no-op instructions when those instructions are in the
-; predecessor but could potentially be sunk.
-; CHECK: @test6
-
-entry:
- %cond1 = load volatile i1* %dummy
- %a.conv = trunc i64 %a to i16
- %b.conv = trunc i64 %b to i16
- br i1 %cond1, label %if, label %end
-
-if:
- %cond2 = load volatile i1* %dummy
- %cond3 = load volatile i1* %dummy
- %cond4 = load volatile i1* %dummy
- %cmp = icmp ult i16 %a.conv, %b.conv
- %a.conv2 = trunc i64 %a to i32
- %b.conv2 = trunc i64 %b to i32
- br i1 %cond2, label %then, label %end
-
-then:
- %sub = sub i32 %a.conv2, %b.conv2
- %sub.conv = trunc i32 %sub to i16
- br label %end
-
-end:
- %x = phi i16 [ %a.conv, %entry ], [ %b.conv, %if ], [ %sub.conv, %then ]
-; CHECK-NOT: phi
-; CHECK: select i1
-
- ret i16 %x
-}
-
-define i16 @test7(i1* %dummy, i16 %a, i16 %b, i32 %x) {
-; Test that we don't speculate when there are instructions that could
-; potentially sink into the conditional block.
-; CHECK: @test7
-
-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
- %a.conv2 = add i32 %a.conv, %x
- br i1 %cond2, label %then, label %end
-
-then:
- %sub = sub i32 %a.conv2, %b.conv
- %sub.conv = trunc i32 %sub to i16
- br label %end
-
-end:
- %y = phi i16 [ %a, %entry ], [ %b, %if ], [ %sub.conv, %then ]
-; CHECK-NOT: select
-; CHECK: phi i16
-
- ret i16 %y
-}
-
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2024-11-26 00:11:24 +0000