[PATCH] D92066: [LAA] Relax restrictions on early exits in loop structure
Philip Reames via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 14 12:44:30 PST 2020
This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGf5fe8493e5ac: [LAA] Relax restrictions on early exits in loop structure (authored by reames).
Changed prior to commit:
https://reviews.llvm.org/D92066?vs=307490&id=311674#toc
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D92066/new/
https://reviews.llvm.org/D92066
Files:
llvm/lib/Analysis/LoopAccessAnalysis.cpp
llvm/lib/Transforms/Scalar/LoopDistribute.cpp
llvm/lib/Transforms/Scalar/LoopLoadElimination.cpp
llvm/lib/Transforms/Utils/LoopVersioning.cpp
Index: llvm/lib/Transforms/Utils/LoopVersioning.cpp
===================================================================
--- llvm/lib/Transforms/Utils/LoopVersioning.cpp
+++ llvm/lib/Transforms/Utils/LoopVersioning.cpp
@@ -269,8 +269,11 @@
// Now walk the identified inner loops.
bool Changed = false;
for (Loop *L : Worklist) {
+ if (!L->isLoopSimplifyForm() || !L->isRotatedForm() ||
+ !L->getExitingBlock())
+ continue;
const LoopAccessInfo &LAI = GetLAA(*L);
- if (L->isLoopSimplifyForm() && !LAI.hasConvergentOp() &&
+ if (!LAI.hasConvergentOp() &&
(LAI.getNumRuntimePointerChecks() ||
!LAI.getPSE().getUnionPredicate().isAlwaysTrue())) {
LoopVersioning LVer(LAI, LAI.getRuntimePointerChecking()->getChecks(), L,
Index: llvm/lib/Transforms/Scalar/LoopLoadElimination.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopLoadElimination.cpp
+++ llvm/lib/Transforms/Scalar/LoopLoadElimination.cpp
@@ -632,6 +632,9 @@
// Now walk the identified inner loops.
for (Loop *L : Worklist) {
+ // Match historical behavior
+ if (!L->isRotatedForm() || !L->getExitingBlock())
+ continue;
// The actual work is performed by LoadEliminationForLoop.
LoadEliminationForLoop LEL(L, &LI, GetLAI(*L), &DT, BFI, PSI);
Changed |= LEL.processLoop();
Index: llvm/lib/Transforms/Scalar/LoopDistribute.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopDistribute.cpp
+++ llvm/lib/Transforms/Scalar/LoopDistribute.cpp
@@ -670,15 +670,17 @@
<< L->getHeader()->getParent()->getName()
<< "\" checking " << *L << "\n");
+ // Having a single exit block implies there's also one exiting block.
if (!L->getExitBlock())
return fail("MultipleExitBlocks", "multiple exit blocks");
if (!L->isLoopSimplifyForm())
return fail("NotLoopSimplifyForm",
"loop is not in loop-simplify form");
+ if (!L->isRotatedForm())
+ return fail("NotBottomTested", "loop is not bottom tested");
BasicBlock *PH = L->getLoopPreheader();
- // LAA will check that we only have a single exiting block.
LAI = &GetLAA(*L);
// Currently, we only distribute to isolate the part of the loop with
Index: llvm/lib/Analysis/LoopAccessAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -1781,26 +1781,6 @@
return false;
}
- // We must have a single exiting block.
- if (!TheLoop->getExitingBlock()) {
- LLVM_DEBUG(
- dbgs() << "LAA: loop control flow is not understood by analyzer\n");
- recordAnalysis("CFGNotUnderstood")
- << "loop control flow is not understood by analyzer";
- return false;
- }
-
- // We only handle bottom-tested loops, i.e. loop in which the condition is
- // checked at the end of each iteration. With that we can assume that all
- // instructions in the loop are executed the same number of times.
- if (TheLoop->getExitingBlock() != TheLoop->getLoopLatch()) {
- LLVM_DEBUG(
- dbgs() << "LAA: loop control flow is not understood by analyzer\n");
- recordAnalysis("CFGNotUnderstood")
- << "loop control flow is not understood by analyzer";
- return false;
- }
-
// ScalarEvolution needs to be able to find the exit count.
const SCEV *ExitCount = PSE->getBackedgeTakenCount();
if (isa<SCEVCouldNotCompute>(ExitCount)) {
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