[llvm] 9e93143 - [SCEV] Support clearing Block/LoopDispositions for a single value.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Fri Oct 7 08:07:46 PDT 2022
Author: Florian Hahn
Date: 2022-10-07T16:07:17+01:00
New Revision: 9e931439ddb9b6b8f655940b9d8ed6db50c2a7e2
URL: https://github.com/llvm/llvm-project/commit/9e931439ddb9b6b8f655940b9d8ed6db50c2a7e2
DIFF: https://github.com/llvm/llvm-project/commit/9e931439ddb9b6b8f655940b9d8ed6db50c2a7e2.diff
LOG: [SCEV] Support clearing Block/LoopDispositions for a single value.
Extend forgetBlockAndLoopDisposition to allow clearing information for a
single value. This can be useful when only a single value is changed,
e.g. because the instruction is moved.
We also need to clear the cached values for all SCEV users, because they
may depend on the starting value's disposition.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D134614
Added:
Modified:
llvm/include/llvm/Analysis/ScalarEvolution.h
llvm/lib/Analysis/ScalarEvolution.cpp
llvm/lib/Transforms/Scalar/LoopDeletion.cpp
llvm/lib/Transforms/Scalar/LoopSink.cpp
llvm/lib/Transforms/Utils/LoopSimplify.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/Analysis/ScalarEvolution.h b/llvm/include/llvm/Analysis/ScalarEvolution.h
index 83f8a9e94bfe6..580fef9f7a5d6 100644
--- a/llvm/include/llvm/Analysis/ScalarEvolution.h
+++ b/llvm/include/llvm/Analysis/ScalarEvolution.h
@@ -944,7 +944,7 @@ class ScalarEvolution {
///
/// We don't have a way to invalidate per-loop/per-block dispositions. Clear
/// and recompute is simpler.
- void forgetBlockAndLoopDispositions();
+ void forgetBlockAndLoopDispositions(Value *V = nullptr);
/// Determine the minimum number of zero bits that S is guaranteed to end in
/// (at every loop iteration). It is, at the same time, the minimum number
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index ac36aba386682..932be39358656 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -8384,9 +8384,36 @@ void ScalarEvolution::forgetValue(Value *V) {
void ScalarEvolution::forgetLoopDispositions() { LoopDispositions.clear(); }
-void ScalarEvolution::forgetBlockAndLoopDispositions() {
- BlockDispositions.clear();
- LoopDispositions.clear();
+void ScalarEvolution::forgetBlockAndLoopDispositions(Value *V) {
+ // Unless a specific value is passed to invalidation, completely clear both
+ // caches.
+ if (!V) {
+ BlockDispositions.clear();
+ LoopDispositions.clear();
+ return;
+ }
+
+ const SCEV *S = getExistingSCEV(V);
+ if (!S)
+ return;
+
+ // Invalidate the block and loop dispositions cached for S. Dispositions of
+ // S's users may change if S's disposition changes (i.e. a user may change to
+ // loop-invariant, if S changes to loop invariant), so also invalidate
+ // dispositions of S's users recursively.
+ SmallVector<const SCEV *, 8> Worklist = {S};
+ SmallPtrSet<const SCEV *, 8> Seen = {S};
+ while (!Worklist.empty()) {
+ const SCEV *Curr = Worklist.pop_back_val();
+ if (!LoopDispositions.erase(Curr) && !BlockDispositions.erase(S))
+ continue;
+
+ auto Users = SCEVUsers.find(Curr);
+ if (Users != SCEVUsers.end())
+ for (const auto *User : Users->second)
+ if (Seen.insert(User).second)
+ Worklist.push_back(User);
+ }
}
/// Get the exact loop backedge taken count considering all loop exits. A
diff --git a/llvm/lib/Transforms/Scalar/LoopDeletion.cpp b/llvm/lib/Transforms/Scalar/LoopDeletion.cpp
index d969126b3ad26..f19f53e8153d3 100644
--- a/llvm/lib/Transforms/Scalar/LoopDeletion.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopDeletion.cpp
@@ -90,22 +90,21 @@ static bool isLoopDead(Loop *L, ScalarEvolution &SE,
break;
if (Instruction *I = dyn_cast<Instruction>(incoming)) {
- if (!L->makeLoopInvariant(I, Changed, Preheader->getTerminator())) {
+ bool InstrMoved = false;
+ if (!L->makeLoopInvariant(I, InstrMoved, Preheader->getTerminator())) {
AllEntriesInvariant = false;
break;
}
- if (Changed) {
+ Changed |= InstrMoved;
+ if (InstrMoved) {
// Moving I to a
diff erent location may change its block disposition,
// so invalidate its SCEV.
- SE.forgetValue(I);
+ SE.forgetBlockAndLoopDispositions(I);
}
}
}
}
- if (Changed)
- SE.forgetLoopDispositions();
-
if (!AllEntriesInvariant || !AllOutgoingValuesSame)
return false;
diff --git a/llvm/lib/Transforms/Scalar/LoopSink.cpp b/llvm/lib/Transforms/Scalar/LoopSink.cpp
index 131af32e870db..ff937273428e4 100644
--- a/llvm/lib/Transforms/Scalar/LoopSink.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopSink.cpp
@@ -312,12 +312,13 @@ static bool sinkLoopInvariantInstructions(Loop &L, AAResults &AA, LoopInfo &LI,
if (!canSinkOrHoistInst(I, &AA, &DT, &L, MSSAU, false, LICMFlags))
continue;
if (sinkInstruction(L, I, ColdLoopBBs, LoopBlockNumber, LI, DT, BFI,
- &MSSAU))
+ &MSSAU)) {
Changed = true;
+ if (SE)
+ SE->forgetBlockAndLoopDispositions(&I);
+ }
}
- if (Changed && SE)
- SE->forgetLoopDispositions();
return Changed;
}
diff --git a/llvm/lib/Transforms/Utils/LoopSimplify.cpp b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
index 16085f47449a5..f247a7eb33f87 100644
--- a/llvm/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
@@ -647,20 +647,22 @@ static bool simplifyOneLoop(Loop *L, SmallVectorImpl<Loop *> &Worklist,
Instruction *Inst = &*I++;
if (Inst == CI)
continue;
+ bool InstInvariant = false;
if (!L->makeLoopInvariant(
- Inst, AnyInvariant,
+ Inst, InstInvariant,
Preheader ? Preheader->getTerminator() : nullptr, MSSAU)) {
AllInvariant = false;
break;
}
+ if (InstInvariant && SE) {
+ // The loop disposition of all SCEV expressions that depend on any
+ // hoisted values have also changed.
+ SE->forgetBlockAndLoopDispositions(Inst);
+ }
+ AnyInvariant |= InstInvariant;
}
- if (AnyInvariant) {
+ if (AnyInvariant)
Changed = true;
- // The loop disposition of all SCEV expressions that depend on any
- // hoisted values have also changed.
- if (SE)
- SE->forgetLoopDispositions();
- }
if (!AllInvariant) continue;
// The block has now been cleared of all instructions except for
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