[llvm] r268406 - [LoopDeletion] Clear SCEV loop dispositions
Sanjoy Das via llvm-commits
llvm-commits at lists.llvm.org
Tue May 3 10:50:02 PDT 2016
Author: sanjoy
Date: Tue May 3 12:50:02 2016
New Revision: 268406
URL: http://llvm.org/viewvc/llvm-project?rev=268406&view=rev
Log:
[LoopDeletion] Clear SCEV loop dispositions
`Loop::makeLoopInvariant` can hoist instructions out of loops, so loop
dispositions for the loop it operated on may need to be cleared. We can
be smarter here (especially around how `forgetLoopDispositions` is
implemented), but let's be correct first.
Fixes PR27570.
Added:
llvm/trunk/test/Transforms/LoopDeletion/update-scev.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp?rev=268406&r1=268405&r2=268406&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopDeletion.cpp Tue May 3 12:50:02 2016
@@ -44,10 +44,10 @@ namespace {
}
private:
- bool isLoopDead(Loop *L, SmallVectorImpl<BasicBlock *> &exitingBlocks,
- SmallVectorImpl<BasicBlock *> &exitBlocks,
- bool &Changed, BasicBlock *Preheader);
-
+ bool isLoopDead(Loop *L, ScalarEvolution &SE,
+ SmallVectorImpl<BasicBlock *> &exitingBlocks,
+ SmallVectorImpl<BasicBlock *> &exitBlocks, bool &Changed,
+ BasicBlock *Preheader);
};
}
@@ -65,7 +65,7 @@ Pass *llvm::createLoopDeletionPass() {
/// isLoopDead - Determined if a loop is dead. This assumes that we've already
/// checked for unique exit and exiting blocks, and that the code is in LCSSA
/// form.
-bool LoopDeletion::isLoopDead(Loop *L,
+bool LoopDeletion::isLoopDead(Loop *L, ScalarEvolution &SE,
SmallVectorImpl<BasicBlock *> &exitingBlocks,
SmallVectorImpl<BasicBlock *> &exitBlocks,
bool &Changed, BasicBlock *Preheader) {
@@ -77,6 +77,8 @@ bool LoopDeletion::isLoopDead(Loop *L,
// sufficient to guarantee that no loop-variant values are used outside
// of the loop.
BasicBlock::iterator BI = exitBlock->begin();
+ bool AllEntriesInvariant = true;
+ bool AllOutgoingValuesSame = true;
while (PHINode *P = dyn_cast<PHINode>(BI)) {
Value *incoming = P->getIncomingValueForBlock(exitingBlocks[0]);
@@ -85,17 +87,30 @@ bool LoopDeletion::isLoopDead(Loop *L,
// blocks, then it is impossible to statically determine which value should
// be used.
for (unsigned i = 1, e = exitingBlocks.size(); i < e; ++i) {
- if (incoming != P->getIncomingValueForBlock(exitingBlocks[i]))
- return false;
+ if (incoming != P->getIncomingValueForBlock(exitingBlocks[i])) {
+ AllOutgoingValuesSame = false;
+ break;
+ }
}
+ if (!AllOutgoingValuesSame)
+ break;
+
if (Instruction *I = dyn_cast<Instruction>(incoming))
- if (!L->makeLoopInvariant(I, Changed, Preheader->getTerminator()))
- return false;
+ if (!L->makeLoopInvariant(I, Changed, Preheader->getTerminator())) {
+ AllEntriesInvariant = false;
+ break;
+ }
++BI;
}
+ if (Changed)
+ SE.forgetLoopDispositions(L);
+
+ if (!AllEntriesInvariant || !AllOutgoingValuesSame)
+ return false;
+
// Make sure that no instructions in the block have potential side-effects.
// This includes instructions that could write to memory, and loads that are
// marked volatile. This could be made more aggressive by using aliasing
@@ -153,14 +168,15 @@ bool LoopDeletion::runOnLoop(Loop *L, LP
if (exitBlocks.size() != 1)
return false;
+ ScalarEvolution &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
+
// Finally, we have to check that the loop really is dead.
bool Changed = false;
- if (!isLoopDead(L, exitingBlocks, exitBlocks, Changed, preheader))
+ if (!isLoopDead(L, SE, exitingBlocks, exitBlocks, Changed, preheader))
return Changed;
// 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.
- ScalarEvolution &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
const SCEV *S = SE.getMaxBackedgeTakenCount(L);
if (isa<SCEVCouldNotCompute>(S))
return Changed;
Added: llvm/trunk/test/Transforms/LoopDeletion/update-scev.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopDeletion/update-scev.ll?rev=268406&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopDeletion/update-scev.ll (added)
+++ llvm/trunk/test/Transforms/LoopDeletion/update-scev.ll Tue May 3 12:50:02 2016
@@ -0,0 +1,56 @@
+; RUN: opt -S -analyze -scalar-evolution -loop-deletion -scalar-evolution < %s | FileCheck %s --check-prefix=SCEV-EXPRS
+; RUN: opt -S -loop-deletion < %s | FileCheck %s --check-prefix=IR-AFTER-TRANSFORM
+; RUN: opt -S -indvars -loop-deletion -indvars < %s | FileCheck %s --check-prefix=ORIGINAL-CRASH
+
+; Checking for a crash. Loop-deletion would change the loop
+; disposition of an instruction, but not update SCEV.
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.11.0"
+
+define void @pr27570() {
+; IR-AFTER-TRANSFORM-LABEL: @pr27570(
+; ORIGINAL-CRASH: @pr27570(
+entry:
+ br label %for.cond
+
+for.cond: ; preds = %for.cond14, %entry
+ %f.0 = phi i32 [ 20, %entry ], [ 0, %for.cond14 ]
+ br label %for.body
+
+for.body: ; preds = %for.inc11, %for.cond
+; IR-AFTER-TRANSFORM: for.body:
+; IR-AFTER-TRANSFORM: %cmp = icmp eq i32 %val, -1
+; IR-AFTER-TRANSFORM: %conv7 = zext i1 %cmp to i32
+; IR-AFTER-TRANSFORM: for.body6:
+
+; SCEV-EXPRS: %conv7 = zext i1 %cmp to i32
+; SCEV-EXPRS: %conv7 = zext i1 %cmp to i32
+; SCEV-EXPRS-NEXT: --> {{.*}} LoopDispositions: { %for.body: Variant, %for.cond: Variant, %for.body6: Invariant }
+ %val = phi i32 [ -20, %for.cond ], [ %inc12, %for.inc11 ]
+ %g.040 = phi i32 [ -20, %for.cond ], [ %and.lcssa, %for.inc11 ]
+ br label %for.body6
+
+for.body6: ; preds = %for.body6, %for.body
+ %h.039 = phi i32 [ 1, %for.body ], [ %inc, %for.body6 ]
+ %g.138 = phi i32 [ %g.040, %for.body ], [ %and, %for.body6 ]
+ %cmp = icmp eq i32 %val, -1
+ %conv7 = zext i1 %cmp to i32
+ %add.i = add nsw i32 %conv7, %h.039
+ %sext = shl i32 %add.i, 24
+ %conv8 = ashr exact i32 %sext, 24
+ %cmp9 = icmp eq i32 %conv8, %f.0
+ %conv10 = zext i1 %cmp9 to i32
+ %and = and i32 %conv10, %g.138
+ %inc = add i32 %h.039, 1
+ br i1 undef, label %for.inc11, label %for.body6
+
+for.inc11: ; preds = %for.body6
+ %and.lcssa = phi i32 [ %and, %for.body6 ]
+ %inc12 = add nsw i32 %val, 1
+ %tobool = icmp eq i32 %inc12, 0
+ br i1 %tobool, label %for.cond14, label %for.body
+
+for.cond14: ; preds = %for.cond14, %for.inc11
+ br i1 undef, label %for.cond, label %for.cond14
+}
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