[PATCH] D46775: [LICM] Preserve DT and LoopInfo specifically

[Jun Bum Lim via Phabricator via llvm-commits]

junbuml created this revision.
junbuml added reviewers: uabelho, davide, dberlin, Ka-Ka.
Herald added a subscriber: mcrosier.

In LICM, CFG could be changed in splitPredecessorsOfLoopExit(), which update
only DT and LoopInfo. Therefore, we should preserve only DT and LoopInfo specifically,
instead of all analyses that depend on the CFG (setPreservesCFG()).

This change should fix PR37323.


https://reviews.llvm.org/D46775

Files:
  lib/Transforms/Scalar/LICM.cpp
  test/Transforms/LICM/pr37323.ll


Index: test/Transforms/LICM/pr37323.ll
===================================================================
--- /dev/null
+++ test/Transforms/LICM/pr37323.ll
@@ -0,0 +1,32 @@
+;RUN: opt -loop-simplify -postdomtree -licm -adce -S -o - %s | FileCheck %s
+;RUN: opt -passes='loop-simplify,require<postdomtree>,require<opt-remark-emit>,loop(licm),function(adce)' -S -o - %s | FileCheck %s
+
+target triple = "x86_64-unknown-linux-gnu"
+
+ at c = external global i16, align 1
+
+;Make sure this test do not crash while accessing PostDomTree which is not
+;preserved in LICM.
+;
+;CHECK-LABEL: fn1()
+;CHECK-LABEL: for.cond.loopexit.split.loop.exit
+;CHECK-LABEL: for.cond.loopexit.split.loop.exit1
+define void @fn1() {
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %if.end, %for.cond1, %entry
+  %0 = phi i16 [ undef, %entry ], [ ptrtoint (i16* @c to i16), %if.end ], [ %.mux, %for.cond1 ]
+  br i1 undef, label %for.cond1, label %for.end8
+
+for.cond1:                                        ; preds = %if.end, %for.cond
+  %.mux = select i1 undef, i16 undef, i16 ptrtoint (i16* @c to i16)
+  br i1 undef, label %for.cond, label %if.end
+
+if.end:                                           ; preds = %for.cond1
+  br i1 undef, label %for.cond, label %for.cond1
+
+for.end8:                                         ; preds = %for.cond
+  ret void
+}
+
Index: lib/Transforms/Scalar/LICM.cpp
===================================================================
--- lib/Transforms/Scalar/LICM.cpp
+++ lib/Transforms/Scalar/LICM.cpp
@@ -170,7 +170,8 @@
   /// loop preheaders be inserted into the CFG...
   ///
   void getAnalysisUsage(AnalysisUsage &AU) const override {
-    AU.setPreservesCFG();
+    AU.addPreserved<DominatorTreeWrapperPass>();
+    AU.addPreserved<LoopInfoWrapperPass>();
     AU.addRequired<TargetLibraryInfoWrapperPass>();
     if (EnableMSSALoopDependency)
       AU.addRequired<MemorySSAWrapperPass>();
@@ -220,7 +221,10 @@
     return PreservedAnalyses::all();
 
   auto PA = getLoopPassPreservedAnalyses();
-  PA.preserveSet<CFGAnalyses>();
+
+  PA.preserve<DominatorTreeAnalysis>();
+  PA.preserve<LoopAnalysis>();
+
   return PA;
 }
 


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