[llvm] 094ccee - Reapply [Dominators] Add findNearestCommonDominator() for Instructions (NFC)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Tue Jan 10 03:20:08 PST 2023
Author: Nikita Popov
Date: 2023-01-10T12:16:31+01:00
New Revision: 094ccee2c89e9fa12a3439f5561f9472f98654e5
URL: https://github.com/llvm/llvm-project/commit/094ccee2c89e9fa12a3439f5561f9472f98654e5
DIFF: https://github.com/llvm/llvm-project/commit/094ccee2c89e9fa12a3439f5561f9472f98654e5.diff
LOG: Reapply [Dominators] Add findNearestCommonDominator() for Instructions (NFC)
Reapply with checks for instructions in unreachable blocks. A test
case for this was added in 1ee4a93b15bb.
-----
This is a recurring pattern: We want to find the nearest common
dominator (instruction) for two instructions, but currently only
provide an API for the nearest common dominator of two basic blocks.
Add an overload that accepts and return instructions.
Added:
Modified:
llvm/include/llvm/IR/Dominators.h
llvm/lib/Analysis/CaptureTracking.cpp
llvm/lib/IR/Dominators.cpp
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
llvm/lib/Transforms/Scalar/TLSVariableHoist.cpp
llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/IR/Dominators.h b/llvm/include/llvm/IR/Dominators.h
index 7fbc7608dea4e..c2d080bc20047 100644
--- a/llvm/include/llvm/IR/Dominators.h
+++ b/llvm/include/llvm/IR/Dominators.h
@@ -219,6 +219,14 @@ class DominatorTree : public DominatorTreeBase<BasicBlock, false> {
/// Provide an overload for a Use.
bool isReachableFromEntry(const Use &U) const;
+ // Ensure base class overloads are visible.
+ using Base::findNearestCommonDominator;
+
+ /// Find the nearest instruction I that dominates both I1 and I2, in the sense
+ /// that a result produced before I will be available at both I1 and I2.
+ Instruction *findNearestCommonDominator(Instruction *I1,
+ Instruction *I2) const;
+
// Pop up a GraphViz/gv window with the Dominator Tree rendered using `dot`.
void viewGraph(const Twine &Name, const Twine &Title);
void viewGraph();
diff --git a/llvm/lib/Analysis/CaptureTracking.cpp b/llvm/lib/Analysis/CaptureTracking.cpp
index f4fd660ac7e06..7f3a2b49aca94 100644
--- a/llvm/lib/Analysis/CaptureTracking.cpp
+++ b/llvm/lib/Analysis/CaptureTracking.cpp
@@ -179,25 +179,10 @@ namespace {
if (EphValues.contains(I))
return false;
- if (!EarliestCapture) {
+ if (!EarliestCapture)
EarliestCapture = I;
- } else if (EarliestCapture->getParent() == I->getParent()) {
- if (I->comesBefore(EarliestCapture))
- EarliestCapture = I;
- } else {
- BasicBlock *CurrentBB = I->getParent();
- BasicBlock *EarliestBB = EarliestCapture->getParent();
- if (DT.dominates(EarliestBB, CurrentBB)) {
- // EarliestCapture already comes before the current use.
- } else if (DT.dominates(CurrentBB, EarliestBB)) {
- EarliestCapture = I;
- } else {
- // Otherwise find the nearest common dominator and use its terminator.
- auto *NearestCommonDom =
- DT.findNearestCommonDominator(CurrentBB, EarliestBB);
- EarliestCapture = NearestCommonDom->getTerminator();
- }
- }
+ else
+ EarliestCapture = DT.findNearestCommonDominator(EarliestCapture, I);
Captured = true;
// Return false to continue analysis; we need to see all potential
diff --git a/llvm/lib/IR/Dominators.cpp b/llvm/lib/IR/Dominators.cpp
index 09be2a8ef6056..7c620c3a9331a 100644
--- a/llvm/lib/IR/Dominators.cpp
+++ b/llvm/lib/IR/Dominators.cpp
@@ -355,6 +355,24 @@ bool DominatorTree::dominates(const BasicBlockEdge &BBE1,
return dominates(BBE1, BBE2.getStart());
}
+Instruction *DominatorTree::findNearestCommonDominator(Instruction *I1,
+ Instruction *I2) const {
+ BasicBlock *BB1 = I1->getParent();
+ BasicBlock *BB2 = I2->getParent();
+ if (BB1 == BB2)
+ return I1->comesBefore(I2) ? I1 : I2;
+ if (!isReachableFromEntry(BB2))
+ return I1;
+ if (!isReachableFromEntry(BB1))
+ return I2;
+ BasicBlock *DomBB = findNearestCommonDominator(BB1, BB2);
+ if (BB1 == DomBB)
+ return I1;
+ if (BB2 == DomBB)
+ return I2;
+ return DomBB->getTerminator();
+}
+
//===----------------------------------------------------------------------===//
// DominatorTreeAnalysis and related pass implementations
//===----------------------------------------------------------------------===//
diff --git a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 7b8bce6657382..6285298b537de 100644
--- a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -2557,15 +2557,8 @@ LSRInstance::OptimizeLoopTermCond() {
// must dominate all the post-inc comparisons we just set up, and it must
// dominate the loop latch edge.
IVIncInsertPos = L->getLoopLatch()->getTerminator();
- for (Instruction *Inst : PostIncs) {
- BasicBlock *BB =
- DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
- Inst->getParent());
- if (BB == Inst->getParent())
- IVIncInsertPos = Inst;
- else if (BB != IVIncInsertPos->getParent())
- IVIncInsertPos = BB->getTerminator();
- }
+ for (Instruction *Inst : PostIncs)
+ IVIncInsertPos = DT.findNearestCommonDominator(IVIncInsertPos, Inst);
}
/// Determine if the given use can accommodate a fixup at the given offset and
diff --git a/llvm/lib/Transforms/Scalar/TLSVariableHoist.cpp b/llvm/lib/Transforms/Scalar/TLSVariableHoist.cpp
index 59edc68684d73..4ec7181ad8595 100644
--- a/llvm/lib/Transforms/Scalar/TLSVariableHoist.cpp
+++ b/llvm/lib/Transforms/Scalar/TLSVariableHoist.cpp
@@ -187,19 +187,7 @@ Instruction *TLSVariableHoistPass::getDomInst(Instruction *I1,
Instruction *I2) {
if (!I1)
return I2;
- if (DT->dominates(I1, I2))
- return I1;
- if (DT->dominates(I2, I1))
- return I2;
-
- // If there is no dominance relation, use common dominator.
- BasicBlock *DomBB =
- DT->findNearestCommonDominator(I1->getParent(), I2->getParent());
-
- Instruction *Dom = DomBB->getTerminator();
- assert(Dom && "Common dominator not found!");
-
- return Dom;
+ return DT->findNearestCommonDominator(I1, I2);
}
BasicBlock::iterator TLSVariableHoistPass::findInsertPos(Function &Fn,
diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index a7fe065c989f0..4e83d2f6e3c61 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -106,13 +106,8 @@ static Instruction *findCommonDominator(ArrayRef<Instruction *> Instructions,
DominatorTree &DT) {
Instruction *CommonDom = nullptr;
for (auto *Insn : Instructions)
- if (!CommonDom || DT.dominates(Insn, CommonDom))
- CommonDom = Insn;
- else if (!DT.dominates(CommonDom, Insn))
- // If there is no dominance relation, use common dominator.
- CommonDom =
- DT.findNearestCommonDominator(CommonDom->getParent(),
- Insn->getParent())->getTerminator();
+ CommonDom =
+ CommonDom ? DT.findNearestCommonDominator(CommonDom, Insn) : Insn;
assert(CommonDom && "Common dominator not found?");
return CommonDom;
}
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