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Revert "[JumpThreading] Simplify Instructions first in ComputeValueKnownInPredecessors()"

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Not sure it handles undef properly.

llvm-svn: 263605
This commit is contained in:
Haicheng Wu 2016-03-15 23:38:47 +00:00
parent ffeaefb7a4
commit ec5b54aa40
2 changed files with 20 additions and 85 deletions
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55
lib/Transforms/Scalar/JumpThreading.cpp
View File

@ -152,7 +152,6 @@ namespace {
bool ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,
PredValueInfo &Result,
ConstantPreference Preference,
bool &Changed,
Instruction *CxtI = nullptr);
bool ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
ConstantPreference Preference,
@ -396,9 +395,10 @@ static Constant *getKnownConstant(Value *Val, ConstantPreference Preference) {
///
/// This returns true if there were any known values.
///
bool JumpThreading::ComputeValueKnownInPredecessors(
Value *V, BasicBlock *BB, PredValueInfo &Result,
ConstantPreference Preference, bool &Changed, Instruction *CxtI) {
bool JumpThreading::
ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
ConstantPreference Preference,
Instruction *CxtI) {
// This method walks up use-def chains recursively. Because of this, we could
// get into an infinite loop going around loops in the use-def chain. To
// prevent this, keep track of what (value, block) pairs we've already visited
@ -410,16 +410,6 @@ bool JumpThreading::ComputeValueKnownInPredecessors(
// stack pops back out again.
RecursionSetRemover remover(RecursionSet, std::make_pair(V, BB));
// Simplify the instruction before inferring the value.
Instruction *I = dyn_cast<Instruction>(V);
if (I && !isa<PHINode>(I))
if (auto *NewV = SimplifyInstruction(I, BB->getModule()->getDataLayout())) {
I->replaceAllUsesWith(NewV);
I->eraseFromParent();
V = NewV;
Changed = true;
}
// If V is a constant, then it is known in all predecessors.
if (Constant *KC = getKnownConstant(V, Preference)) {
for (BasicBlock *Pred : predecessors(BB))
@ -430,7 +420,7 @@ bool JumpThreading::ComputeValueKnownInPredecessors(
// If V is a non-instruction value, or an instruction in a different block,
// then it can't be derived from a PHI.
I = dyn_cast<Instruction>(V);
Instruction *I = dyn_cast<Instruction>(V);
if (!I || I->getParent() != BB) {
// Okay, if this is a live-in value, see if it has a known value at the end
@ -485,9 +475,9 @@ bool JumpThreading::ComputeValueKnownInPredecessors(
if (I->getOpcode() == Instruction::Or ||
I->getOpcode() == Instruction::And) {
ComputeValueKnownInPredecessors(I->getOperand(0), BB, LHSVals,
WantInteger, Changed, CxtI);
WantInteger, CxtI);
ComputeValueKnownInPredecessors(I->getOperand(1), BB, RHSVals,
WantInteger, Changed, CxtI);
WantInteger, CxtI);
if (LHSVals.empty() && RHSVals.empty())
return false;
@ -522,8 +512,8 @@ bool JumpThreading::ComputeValueKnownInPredecessors(
if (I->getOpcode() == Instruction::Xor &&
isa<ConstantInt>(I->getOperand(1)) &&
cast<ConstantInt>(I->getOperand(1))->isOne()) {
ComputeValueKnownInPredecessors(I->getOperand(0), BB, Result, WantInteger,
Changed, CxtI);
ComputeValueKnownInPredecessors(I->getOperand(0), BB, Result,
WantInteger, CxtI);
if (Result.empty())
return false;
@ -541,7 +531,7 @@ bool JumpThreading::ComputeValueKnownInPredecessors(
if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1))) {
PredValueInfoTy LHSVals;
ComputeValueKnownInPredecessors(BO->getOperand(0), BB, LHSVals,
WantInteger, Changed, CxtI);
WantInteger, CxtI);
// Try to use constant folding to simplify the binary operator.
for (const auto &LHSVal : LHSVals) {
@ -618,7 +608,7 @@ bool JumpThreading::ComputeValueKnownInPredecessors(
if (Constant *CmpConst = dyn_cast<Constant>(Cmp->getOperand(1))) {
PredValueInfoTy LHSVals;
ComputeValueKnownInPredecessors(I->getOperand(0), BB, LHSVals,
WantInteger, Changed, CxtI);
WantInteger, CxtI);
for (const auto &LHSVal : LHSVals) {
Constant *V = LHSVal.first;
@ -641,7 +631,7 @@ bool JumpThreading::ComputeValueKnownInPredecessors(
PredValueInfoTy Conds;
if ((TrueVal || FalseVal) &&
ComputeValueKnownInPredecessors(SI->getCondition(), BB, Conds,
WantInteger, Changed, CxtI)) {
WantInteger, CxtI)) {
for (auto &C : Conds) {
Constant *Cond = C.first;
@ -1190,10 +1180,8 @@ bool JumpThreading::ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
return false;
PredValueInfoTy PredValues;
bool Changed = false;
if (!ComputeValueKnownInPredecessors(Cond, BB, PredValues, Preference,
Changed, CxtI))
return Changed;
if (!ComputeValueKnownInPredecessors(Cond, BB, PredValues, Preference, CxtI))
return false;
assert(!PredValues.empty() &&
"ComputeValueKnownInPredecessors returned true with no values");
@ -1251,7 +1239,7 @@ bool JumpThreading::ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
// If all edges were unthreadable, we fail.
if (PredToDestList.empty())
return Changed;
return false;
// Determine which is the most common successor. If we have many inputs and
// this block is a switch, we want to start by threading the batch that goes
@ -1284,8 +1272,7 @@ bool JumpThreading::ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
getSuccessor(GetBestDestForJumpOnUndef(BB));
// Ok, try to thread it!
Changed |= ThreadEdge(BB, PredsToFactor, MostPopularDest);
return Changed;
return ThreadEdge(BB, PredsToFactor, MostPopularDest);
}
/// ProcessBranchOnPHI - We have an otherwise unthreadable conditional branch on
@ -1356,13 +1343,12 @@ bool JumpThreading::ProcessBranchOnXOR(BinaryOperator *BO) {
PredValueInfoTy XorOpValues;
bool isLHS = true;
bool Changed = false;
if (!ComputeValueKnownInPredecessors(BO->getOperand(0), BB, XorOpValues,
WantInteger, Changed, BO)) {
WantInteger, BO)) {
assert(XorOpValues.empty());
if (!ComputeValueKnownInPredecessors(BO->getOperand(1), BB, XorOpValues,
WantInteger, Changed, BO))
return Changed;
WantInteger, BO))
return false;
isLHS = false;
}
@ -1420,8 +1406,7 @@ bool JumpThreading::ProcessBranchOnXOR(BinaryOperator *BO) {
}
// Try to duplicate BB into PredBB.
Changed |= DuplicateCondBranchOnPHIIntoPred(BB, BlocksToFoldInto);
return Changed;
return DuplicateCondBranchOnPHIIntoPred(BB, BlocksToFoldInto);
}

50
test/Transforms/JumpThreading/basic.ll
View File

@ -476,56 +476,6 @@ exit1:
; CHECK: }
}
;;; Verify that we can handle constraint propagation through cast.
define i32 @test16(i1 %cond) {
Entry:
; CHECK-LABEL: @test16(
br i1 %cond, label %Merge, label %F1
; CHECK: Entry:
; CHECK-NEXT: br i1 %cond, label %F2, label %Merge
F1:
%v1 = call i32 @f1()
br label %Merge
Merge:
%B = phi i32 [1, %Entry], [%v1, %F1]
%M = icmp eq i32 %B, 0
%M1 = zext i1 %M to i32
%N = icmp eq i32 %M1, 1
br i1 %N, label %T2, label %F2
; CHECK: Merge:
; CHECK-NOT: phi
; CHECK-NEXT: %v1 = call i32 @f1()
T2:
%Q = zext i1 %M to i32
ret i32 %Q
F2:
ret i32 %B
; CHECK: F2:
; CHECK-NEXT: phi i32
}
;;; Just check that ComputeValueKnownInPredecessors() does not return true with
;;; no values and triggers the assert in ProcessThreadableEdges().
define i32 @test17() {
entry:
%A = add i32 0, 1
%B = icmp eq i32 %A, 0
br i1 %B, label %T, label %F
T:
%v1 = call i32 @f1()
ret i32 %v1
F:
%v2 = call i32 @f2()
ret i32 %v2
}
; In this test we check that block duplication is inhibited by the presence
; of a function with the 'noduplicate' attribute.