[PATCH] D61904: [LICM] Allow AliasSetMap to contain top-level loops.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: asbirlea, sanjoy, chandlerc.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

When an outer loop gets deleted by a different pass, before LICM visits
it, we cannot clean up its sub-loops in AliasSetMap, because at the
point we receive the deleteAnalysisLoop callback for the outer loop, the loop
object is already invalid and we cannot access its sub-loops any longer.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D61904

Files:
  llvm/lib/Transforms/Scalar/LICM.cpp
  llvm/test/Transforms/LICM/outer-loop-deleted-before-licm.ll


Index: llvm/test/Transforms/LICM/outer-loop-deleted-before-licm.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LICM/outer-loop-deleted-before-licm.ll
@@ -0,0 +1,46 @@
+; RUN: opt %s -S -loop-unroll -licm | FileCheck %s
+
+; Check that we can deal with loops where a parent loop gets deleted before it
+; is visited by LICM.
+define void @test() {
+; CHECK-LABEL: define void @test() {
+; CHECK-LABEL: entry:
+; CHECK-NEXT:    br label %for.body43
+
+; CHECK-LABEL: for.body43:                                       ; preds = %entry
+; CHECK-NEXT:    br label %if.else75
+
+; CHECK-LABEL: if.else75:                                        ; preds = %for.body43
+; CHECK-NEXT:    br label %for.body467
+
+; CHECK-LABEL: for.body467:                                      ; preds = %for.body467.for.body467_crit_edge, %if.else75
+; CHECK-NEXT:    br label %for.body467.for.body467_crit_edge
+
+; CHECK-LABEL: for.body467.for.body467_crit_edge:                ; preds = %for.body467
+; CHECK-NEXT:    br i1 false, label %for.end539, label %for.body467
+
+; CHECK-LABEL: for.end539:                                       ; preds = %for.body467.for.body467_crit_edge
+; CHECK-NEXT:    ret void
+;
+
+entry:
+  br label %for.body43
+
+for.body43:                                       ; preds = %for.end539, %entry
+  br label %if.else75
+
+if.else75:                                        ; preds = %for.body43
+  br label %for.body467
+
+for.body467:                                      ; preds = %for.body467.for.body467_crit_edge, %if.else75
+  br label %for.body467.for.body467_crit_edge
+
+for.body467.for.body467_crit_edge:                ; preds = %for.body467
+  br i1 false, label %for.end539, label %for.body467
+
+for.end539:                                       ; preds = %for.body467
+  br i1 undef, label %for.body43, label %for.end547
+
+for.end547:                                       ; preds = %for.body43
+  ret void
+}
Index: llvm/lib/Transforms/Scalar/LICM.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LICM.cpp
+++ llvm/lib/Transforms/Scalar/LICM.cpp
@@ -244,8 +244,16 @@
   using llvm::Pass::doFinalization;
 
   bool doFinalization() override {
-    assert(LICM.getLoopToAliasSetMap().empty() &&
+    auto &AliasSetMap = LICM.getLoopToAliasSetMap();
+    // All loops in the AliasSetMap should be cleaned up already. The only case
+    // where we fail to do so is if an outer loop gets deleted before LICM
+    // visits it.
+    assert(all_of(AliasSetMap,
+                  [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) {
+                    return !KV.first->getParentLoop();
+                  }) &&
            "Didn't free loop alias sets");
+    AliasSetMap.clear();
     return false;
   }
 


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