[llvm] r292332 - [PM] Teach LoopDeletion to correctly update the LPM when loops are
Chandler Carruth via llvm-commits
llvm-commits at lists.llvm.org
Tue Jan 17 18:41:26 PST 2017
Author: chandlerc
Date: Tue Jan 17 20:41:26 2017
New Revision: 292332
URL: http://llvm.org/viewvc/llvm-project?rev=292332&view=rev
Log:
[PM] Teach LoopDeletion to correctly update the LPM when loops are
deleted.
I've expanded its test coverage a bit including adding one test that
will crash clearly without this change.
Added:
llvm/trunk/test/Transforms/LoopDeletion/invalidation.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp
llvm/trunk/test/Transforms/LoopDeletion/multiple-exit-conditions.ll
llvm/trunk/test/Transforms/LoopDeletion/multiple-exits.ll
Modified: llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp?rev=292332&r1=292331&r2=292332&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp Tue Jan 17 20:41:26 2017
@@ -100,12 +100,16 @@ static bool isLoopDead(Loop *L, ScalarEv
/// This entire process relies pretty heavily on LoopSimplify form and LCSSA in
/// order to make various safety checks work.
///
-/// \returns true if any changes are made, even if the loop is not deleted.
+/// \returns true if the loop is deleted.
+///
+/// This also sets the \p Changed output parameter to `true` if any changes
+/// were made. This may mutate the loop even if it is unable to delete it due
+/// to hoisting trivially loop invariant instructions out of the loop.
///
/// This also updates the relevant analysis information in \p DT, \p SE, and \p
/// LI.
static bool deleteLoopIfDead(Loop *L, DominatorTree &DT, ScalarEvolution &SE,
- LoopInfo &LI) {
+ LoopInfo &LI, bool &Changed) {
assert(L->isLCSSAForm(DT) && "Expected LCSSA!");
// We can only remove the loop if there is a preheader that we can
@@ -135,15 +139,14 @@ static bool deleteLoopIfDead(Loop *L, Do
return false;
// Finally, we have to check that the loop really is dead.
- bool Changed = false;
if (!isLoopDead(L, SE, ExitingBlocks, ExitBlock, Changed, Preheader))
- return Changed;
+ return false;
// Don't remove loops for which we can't solve the trip count.
// They could be infinite, in which case we'd be changing program behavior.
const SCEV *S = SE.getMaxBackedgeTakenCount(L);
if (isa<SCEVCouldNotCompute>(S))
- return Changed;
+ return false;
// Now that we know the removal is safe, remove the loop by changing the
// branch from the preheader to go to the single exit block.
@@ -215,15 +218,21 @@ static bool deleteLoopIfDead(Loop *L, Do
++NumDeleted;
- return Changed;
+ return true;
}
PreservedAnalyses LoopDeletionPass::run(Loop &L, LoopAnalysisManager &AM,
LoopStandardAnalysisResults &AR,
- LPMUpdater &) {
- bool Changed = deleteLoopIfDead(&L, AR.DT, AR.SE, AR.LI);
- if (!Changed)
+ LPMUpdater &Updater) {
+ bool Changed = false;
+
+ if (deleteLoopIfDead(&L, AR.DT, AR.SE, AR.LI, Changed)) {
+ assert(Changed && "Cannot delete a loop without changing something!");
+ // Need to update the LPM about this loop going away.
+ Updater.markLoopAsDeleted(L);
+ } else if (!Changed) {
return PreservedAnalyses::all();
+ }
return getLoopPassPreservedAnalyses();
}
@@ -262,5 +271,6 @@ bool LoopDeletionLegacyPass::runOnLoop(L
ScalarEvolution &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
- return deleteLoopIfDead(L, DT, SE, LI);
+ bool Changed = false;
+ return deleteLoopIfDead(L, DT, SE, LI, Changed) || Changed;
}
Added: llvm/trunk/test/Transforms/LoopDeletion/invalidation.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopDeletion/invalidation.ll?rev=292332&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopDeletion/invalidation.ll (added)
+++ llvm/trunk/test/Transforms/LoopDeletion/invalidation.ll Tue Jan 17 20:41:26 2017
@@ -0,0 +1,42 @@
+; Ensure we don't run analyses over loops after they've been deleted. We run
+; one version with a no-op loop pass to make sure that the loop doesn't get
+; simplified away.
+;
+; RUN: opt < %s -passes='require<ivusers>,no-op-loop,require<ivusers>' -S \
+; RUN: | FileCheck %s --check-prefixes=CHECK,BEFORE
+; RUN: opt < %s -passes='require<ivusers>,loop-deletion,require<ivusers>' -S \
+; RUN: | FileCheck %s --check-prefixes=CHECK,AFTER
+
+
+define void @foo(i64 %n, i64 %m) nounwind {
+; CHECK-LABEL: @foo(
+
+entry:
+ br label %bb
+; CHECK: entry:
+; BEFORE-NEXT: br label %bb
+; AFTER-NEXT: br label %return
+
+bb:
+ %x.0 = phi i64 [ 0, %entry ], [ %t0, %bb2 ]
+ %t0 = add i64 %x.0, 1
+ %t1 = icmp slt i64 %x.0, %n
+ br i1 %t1, label %bb2, label %return
+; BEFORE: bb:
+; BEFORE: br i1 {{.*}}, label %bb2, label %return
+; AFTER-NOT: bb:
+; AFTER-NOT: br
+
+bb2:
+ %t2 = icmp slt i64 %x.0, %m
+ br i1 %t1, label %bb, label %return
+; BEFORE: bb2:
+; BEFORE: br i1 {{.*}}, label %bb, label %return
+; AFTER-NOT: bb2:
+; AFTER-NOT: br
+
+return:
+ ret void
+; CHECK: return:
+; CHECK-NEXT: ret void
+}
Modified: llvm/trunk/test/Transforms/LoopDeletion/multiple-exit-conditions.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopDeletion/multiple-exit-conditions.ll?rev=292332&r1=292331&r2=292332&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopDeletion/multiple-exit-conditions.ll (original)
+++ llvm/trunk/test/Transforms/LoopDeletion/multiple-exit-conditions.ll Tue Jan 17 20:41:26 2017
@@ -1,5 +1,5 @@
; RUN: opt < %s -loop-deletion -S | FileCheck %s
-; RUN: opt < %s -passes='require<scalar-evolution>,loop(loop-deletion)' -S | FileCheck %s
+; RUN: opt < %s -passes='loop(loop-deletion)' -S | FileCheck %s
; ScalarEvolution can prove the loop iteration is finite, even though
; it can't represent the exact trip count as an expression. That's
Modified: llvm/trunk/test/Transforms/LoopDeletion/multiple-exits.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopDeletion/multiple-exits.ll?rev=292332&r1=292331&r2=292332&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopDeletion/multiple-exits.ll (original)
+++ llvm/trunk/test/Transforms/LoopDeletion/multiple-exits.ll Tue Jan 17 20:41:26 2017
@@ -5,6 +5,9 @@
;
; RUN: opt < %s -loop-simplify -lcssa -S | FileCheck %s --check-prefixes=CHECK,BEFORE
; RUN: opt < %s -loop-deletion -S | FileCheck %s --check-prefixes=CHECK,AFTER
+;
+; RUN: opt < %s -passes=no-op-loop -S | FileCheck %s --check-prefixes=CHECK,BEFORE
+; RUN: opt < %s -passes=loop-deletion -S | FileCheck %s --check-prefixes=CHECK,AFTER
define void @foo(i64 %n, i64 %m) nounwind {
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