[LV] Replace UncountableEdge with UncountableEarlyExitingBlock (NFC). #151311
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@llvm/pr-subscribers-vectorizers @llvm/pr-subscribers-llvm-transforms Author: Florian Hahn (fhahn) ChangesOnly the uncountable exiting BB is used. Store it instead of a piar of Exiting BB and Exit BB. Full diff: https://github.com/llvm/llvm-project/pull/151311.diff 2 Files Affected:
diff --git a/llvm/include/llvm/Transforms/Vectorize/LoopVectorizationLegality.h b/llvm/include/llvm/Transforms/Vectorize/LoopVectorizationLegality.h
index cba37363d0474..43ff084816d18 100644
--- a/llvm/include/llvm/Transforms/Vectorize/LoopVectorizationLegality.h
+++ b/llvm/include/llvm/Transforms/Vectorize/LoopVectorizationLegality.h
@@ -400,19 +400,11 @@ class LoopVectorizationLegality {
/// Returns true if the loop has exactly one uncountable early exit, i.e. an
/// uncountable exit that isn't the latch block.
- bool hasUncountableEarlyExit() const {
- return getUncountableEdge().has_value();
- }
+ bool hasUncountableEarlyExit() const { return UncountableExitingBB; }
/// Returns the uncountable early exiting block, if there is exactly one.
BasicBlock *getUncountableEarlyExitingBlock() const {
- return hasUncountableEarlyExit() ? getUncountableEdge()->first : nullptr;
- }
-
- /// Returns the destination of the uncountable early exiting block, if there
- /// is exactly one.
- BasicBlock *getUncountableEarlyExitBlock() const {
- return hasUncountableEarlyExit() ? getUncountableEdge()->second : nullptr;
+ return UncountableExitingBB;
}
/// Return true if there is store-load forwarding dependencies.
@@ -473,13 +465,6 @@ class LoopVectorizationLegality {
return CountableExitingBlocks;
}
- /// Returns the loop edge to an uncountable exit, or std::nullopt if there
- /// isn't a single such edge.
- std::optional<std::pair<BasicBlock *, BasicBlock *>>
- getUncountableEdge() const {
- return UncountableEdge;
- }
-
private:
/// Return true if the pre-header, exiting and latch blocks of \p Lp and all
/// its nested loops are considered legal for vectorization. These legal
@@ -659,9 +644,9 @@ class LoopVectorizationLegality {
/// the exact backedge taken count is not computable.
SmallVector<BasicBlock *, 4> CountableExitingBlocks;
- /// Keep track of the loop edge to an uncountable exit, comprising a pair
- /// of (Exiting, Exit) blocks, if there is exactly one early exit.
- std::optional<std::pair<BasicBlock *, BasicBlock *>> UncountableEdge;
+ /// Keep track of an uncountable exiting block, if there is exactly one early
+ /// exit.
+ BasicBlock *UncountableExitingBB = nullptr;
};
} // namespace llvm
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
index 969d225c6ef2e..1e9581c427c68 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -1665,7 +1665,7 @@ bool LoopVectorizationLegality::isVectorizableEarlyExitLoop() {
// Keep a record of all the exiting blocks.
SmallVector<const SCEVPredicate *, 4> Predicates;
- std::optional<std::pair<BasicBlock *, BasicBlock *>> SingleUncountableEdge;
+ BasicBlock *SingleUncountableExitingBlock;
for (BasicBlock *BB : ExitingBlocks) {
const SCEV *EC =
PSE.getSE()->getPredicatedExitCount(TheLoop, BB, &Predicates);
@@ -1687,7 +1687,7 @@ bool LoopVectorizationLegality::isVectorizableEarlyExitLoop() {
ExitBlock = Succs[1];
}
- if (SingleUncountableEdge) {
+ if (SingleUncountableExitingBlock) {
reportVectorizationFailure(
"Loop has too many uncountable exits",
"Cannot vectorize early exit loop with more than one early exit",
@@ -1695,7 +1695,7 @@ bool LoopVectorizationLegality::isVectorizableEarlyExitLoop() {
return false;
}
- SingleUncountableEdge = {BB, ExitBlock};
+ SingleUncountableExitingBlock = BB;
} else
CountableExitingBlocks.push_back(BB);
}
@@ -1705,7 +1705,7 @@ bool LoopVectorizationLegality::isVectorizableEarlyExitLoop() {
// PSE.getSymbolicMaxBackedgeTakenCount() below.
Predicates.clear();
- if (!SingleUncountableEdge) {
+ if (!SingleUncountableExitingBlock) {
LLVM_DEBUG(dbgs() << "LV: Cound not find any uncountable exits");
return false;
}
@@ -1713,7 +1713,7 @@ bool LoopVectorizationLegality::isVectorizableEarlyExitLoop() {
// The only supported early exit loops so far are ones where the early
// exiting block is a unique predecessor of the latch block.
BasicBlock *LatchPredBB = LatchBB->getUniquePredecessor();
- if (LatchPredBB != SingleUncountableEdge->first) {
+ if (LatchPredBB != SingleUncountableExitingBlock) {
reportVectorizationFailure("Early exit is not the latch predecessor",
"Cannot vectorize early exit loop",
"EarlyExitNotLatchPredecessor", ORE, TheLoop);
@@ -1766,7 +1766,7 @@ bool LoopVectorizationLegality::isVectorizableEarlyExitLoop() {
}
// The vectoriser cannot handle loads that occur after the early exit block.
- assert(LatchBB->getUniquePredecessor() == SingleUncountableEdge->first &&
+ assert(LatchBB->getUniquePredecessor() == SingleUncountableExitingBlock &&
"Expected latch predecessor to be the early exiting block");
// TODO: Handle loops that may fault.
@@ -1789,7 +1789,7 @@ bool LoopVectorizationLegality::isVectorizableEarlyExitLoop() {
LLVM_DEBUG(dbgs() << "LV: Found an early exit loop with symbolic max "
"backedge taken count: "
<< *SymbolicMaxBTC << '\n');
- UncountableEdge = SingleUncountableEdge;
+ UncountableExitingBB = SingleUncountableExitingBlock;
return true;
}
@@ -1861,7 +1861,8 @@ bool LoopVectorizationLegality::canVectorize(bool UseVPlanNativePath) {
return false;
} else {
if (!isVectorizableEarlyExitLoop()) {
- UncountableEdge = std::nullopt;
+ assert(!hasUncountableEarlyExit() &&
+ "Must be false without vectorizable early-exit loop");
if (DoExtraAnalysis)
Result = false;
else
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Looks like there are some failures on Linux/Windows, which I cannot reproduce on macOS. Will need to check what the issue is |
david-arm
reviewed
Jul 31, 2025
| @@ -1665,7 +1665,7 @@ bool LoopVectorizationLegality::isVectorizableEarlyExitLoop() { | |||
|
|
|||
| // Keep a record of all the exiting blocks. | |||
| SmallVector<const SCEVPredicate *, 4> Predicates; | |||
| std::optional<std::pair<BasicBlock *, BasicBlock *>> SingleUncountableEdge; | |||
| BasicBlock *SingleUncountableExitingBlock; | |||
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Could the build issue be due to this uninitialised variable?
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Ah yes, thanks, fixed. Looks like my local compiler was zero-initializing local variables...
Only the uncountable exiting BB is used. Store it instead of a piar of Exiting BB and Exit BB.
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/51/builds/20800 Here is the relevant piece of the build log for the reference |
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…lock (NFC). (#151311) Only the uncountable exiting BB is used. Store it instead of a piar of Exiting BB and Exit BB. PR: llvm/llvm-project#151311
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/168/builds/14806 Here is the relevant piece of the build log for the reference |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/72/builds/13716 Here is the relevant piece of the build log for the reference |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/66/builds/17331 Here is the relevant piece of the build log for the reference |
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Clean up unused/dead variables after 965231c (llvm/llvm-project#151311)
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Only the uncountable exiting BB is used. Store it instead of a piar of Exiting BB and Exit BB.