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[SimplifyCFG] Revise common code sinking
- Fix the case where more than 1 common instructions derived from the same operand cannot be sunk. When a pair of value has more than 1 derived values in both branches, only 1 derived value could be sunk. - Replace BB1 -> (BB2, PN) map with joint value map, i.e. map of (BB1, BB2) -> PN, which is more accurate to track common ops. llvm-svn: 224757
This commit is contained in:
Michael Liao
parent
9dee8a54d7
commit
e7760832e1
@ -1244,14 +1244,13 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
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return false;
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// Gather the PHI nodes in BBEnd.
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std::map<Value*, std::pair<Value*, PHINode*> > MapValueFromBB1ToBB2;
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SmallDenseMap<std::pair<Value *, Value *>, PHINode *> JointValueMap;
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Instruction *FirstNonPhiInBBEnd = nullptr;
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for (BasicBlock::iterator I = BBEnd->begin(), E = BBEnd->end();
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I != E; ++I) {
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for (BasicBlock::iterator I = BBEnd->begin(), E = BBEnd->end(); I != E; ++I) {
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if (PHINode *PN = dyn_cast<PHINode>(I)) {
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Value *BB1V = PN->getIncomingValueForBlock(BB1);
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Value *BB2V = PN->getIncomingValueForBlock(BB2);
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MapValueFromBB1ToBB2[BB1V] = std::make_pair(BB2V, PN);
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JointValueMap[std::make_pair(BB1V, BB2V)] = PN;
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} else {
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FirstNonPhiInBBEnd = &*I;
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break;
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@ -1260,12 +1259,12 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
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if (!FirstNonPhiInBBEnd)
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return false;
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// This does very trivial matching, with limited scanning, to find identical
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// instructions in the two blocks. We scan backward for obviously identical
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// instructions in an identical order.
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BasicBlock::InstListType::reverse_iterator RI1 = BB1->getInstList().rbegin(),
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RE1 = BB1->getInstList().rend(), RI2 = BB2->getInstList().rbegin(),
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RE1 = BB1->getInstList().rend(),
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RI2 = BB2->getInstList().rbegin(),
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RE2 = BB2->getInstList().rend();
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// Skip debug info.
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while (RI1 != RE1 && isa<DbgInfoIntrinsic>(&*RI1)) ++RI1;
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@ -1289,6 +1288,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
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return Changed;
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Instruction *I1 = &*RI1, *I2 = &*RI2;
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auto InstPair = std::make_pair(I1, I2);
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// I1 and I2 should have a single use in the same PHI node, and they
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// perform the same operation.
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// Cannot move control-flow-involving, volatile loads, vaarg, etc.
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@ -1299,11 +1299,11 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
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I1->mayHaveSideEffects() || I2->mayHaveSideEffects() ||
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I1->mayReadOrWriteMemory() || I2->mayReadOrWriteMemory() ||
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!I1->hasOneUse() || !I2->hasOneUse() ||
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MapValueFromBB1ToBB2.find(I1) == MapValueFromBB1ToBB2.end() ||
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MapValueFromBB1ToBB2[I1].first != I2)
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!JointValueMap.count(InstPair))
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return Changed;
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// Check whether we should swap the operands of ICmpInst.
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// TODO: Add support of communativity.
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ICmpInst *ICmp1 = dyn_cast<ICmpInst>(I1), *ICmp2 = dyn_cast<ICmpInst>(I2);
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bool SwapOpnds = false;
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if (ICmp1 && ICmp2 &&
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@ -1324,16 +1324,13 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
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// with a PHI node after sinking. We only handle the case where there is
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// a single pair of different operands.
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Value *DifferentOp1 = nullptr, *DifferentOp2 = nullptr;
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unsigned Op1Idx = 0;
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unsigned Op1Idx = ~0U;
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for (unsigned I = 0, E = I1->getNumOperands(); I != E; ++I) {
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if (I1->getOperand(I) == I2->getOperand(I))
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continue;
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// Early exit if we have more-than one pair of different operands or
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// the different operand is already in MapValueFromBB1ToBB2.
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// Early exit if we need a PHI node to replace a constant.
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if (DifferentOp1 ||
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MapValueFromBB1ToBB2.find(I1->getOperand(I)) !=
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MapValueFromBB1ToBB2.end() ||
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// Early exit if we have more-than one pair of different operands or if
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// we need a PHI node to replace a constant.
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if (Op1Idx != ~0U ||
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isa<Constant>(I1->getOperand(I)) ||
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isa<Constant>(I2->getOperand(I))) {
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// If we can't sink the instructions, undo the swapping.
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@ -1346,24 +1343,27 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
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DifferentOp2 = I2->getOperand(I);
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}
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// We insert the pair of different operands to MapValueFromBB1ToBB2 and
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// remove (I1, I2) from MapValueFromBB1ToBB2.
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if (DifferentOp1) {
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PHINode *NewPN = PHINode::Create(DifferentOp1->getType(), 2,
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DifferentOp1->getName() + ".sink",
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BBEnd->begin());
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MapValueFromBB1ToBB2[DifferentOp1] = std::make_pair(DifferentOp2, NewPN);
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// I1 should use NewPN instead of DifferentOp1.
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I1->setOperand(Op1Idx, NewPN);
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DEBUG(dbgs() << "SINK common instructions " << *I1 << "\n");
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DEBUG(dbgs() << " " << *I2 << "\n");
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// We insert the pair of different operands to JointValueMap and
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// remove (I1, I2) from JointValueMap.
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if (Op1Idx != ~0U) {
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auto &NewPN = JointValueMap[std::make_pair(DifferentOp1, DifferentOp2)];
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if (!NewPN) {
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NewPN =
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PHINode::Create(DifferentOp1->getType(), 2,
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DifferentOp1->getName() + ".sink", BBEnd->begin());
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NewPN->addIncoming(DifferentOp1, BB1);
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NewPN->addIncoming(DifferentOp2, BB2);
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DEBUG(dbgs() << "Create PHI node " << *NewPN << "\n";);
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}
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PHINode *OldPN = MapValueFromBB1ToBB2[I1].second;
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MapValueFromBB1ToBB2.erase(I1);
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// I1 should use NewPN instead of DifferentOp1.
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I1->setOperand(Op1Idx, NewPN);
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}
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PHINode *OldPN = JointValueMap[InstPair];
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JointValueMap.erase(InstPair);
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DEBUG(dbgs() << "SINK common instructions " << *I1 << "\n";);
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DEBUG(dbgs() << " " << *I2 << "\n";);
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// We need to update RE1 and RE2 if we are going to sink the first
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// instruction in the basic block down.
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bool UpdateRE1 = (I1 == BB1->begin()), UpdateRE2 = (I2 == BB2->begin());
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@ -4,7 +4,7 @@ define zeroext i1 @test1(i1 zeroext %flag, i32 %blksA, i32 %blksB, i32 %nblks) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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; CHECK: test1
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; CHECK-LABEL: test1
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; CHECK: add
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; CHECK: select
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; CHECK: icmp
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@ -30,7 +30,7 @@ define zeroext i1 @test2(i1 zeroext %flag, i32 %blksA, i32 %blksB, i32 %nblks) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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; CHECK: test2
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; CHECK-LABEL: test2
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; CHECK: add
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; CHECK: select
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; CHECK: icmp
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@ -51,3 +51,33 @@ if.end:
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%tobool4 = icmp ne i8 %obeys.0, 0
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ret i1 %tobool4
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}
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declare i32 @foo(i32, i32) nounwind readnone
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define i32 @test3(i1 zeroext %flag, i32 %x, i32 %y) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%x0 = call i32 @foo(i32 %x, i32 0) nounwind readnone
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%y0 = call i32 @foo(i32 %x, i32 1) nounwind readnone
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br label %if.end
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if.else:
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%x1 = call i32 @foo(i32 %y, i32 0) nounwind readnone
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%y1 = call i32 @foo(i32 %y, i32 1) nounwind readnone
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br label %if.end
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if.end:
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%xx = phi i32 [ %x0, %if.then ], [ %x1, %if.else ]
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%yy = phi i32 [ %y0, %if.then ], [ %y1, %if.else ]
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%ret = add i32 %xx, %yy
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ret i32 %ret
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}
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; CHECK-LABEL: test3
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; CHECK: select
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; CHECK: call
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; CHECK: call
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; CHECK: add
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; CHECK-NOT: br
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