[PATCH] D91153: [IndVarSimplify] Fix Modified status when handling dead PHI nodes

[David Stenberg via Phabricator via llvm-commits]

dstenb updated this revision to Diff 307714.
dstenb added a comment.

Use X86 reproducer instead.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D91153/new/

https://reviews.llvm.org/D91153

Files:
  llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
  llvm/test/Transforms/IndVarSimplify/rewrite-loop-exit-values-phi.ll


Index: llvm/test/Transforms/IndVarSimplify/rewrite-loop-exit-values-phi.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/IndVarSimplify/rewrite-loop-exit-values-phi.ll
@@ -0,0 +1,51 @@
+; RUN: opt -indvars -S %s -o - | FileCheck %s
+
+; When bailing out in rewriteLoopExitValues() you would be left with a PHI node
+; that was not deleted, and the IndVar pass would return an incorrect modified
+; status. This was caught by the expensive check introduced in D86589.
+
+; CHECK-LABEL: header:
+; CHECK-NEXT: %idx = phi i64 [ %idx.next, %latch ], [ undef, %entry ]
+; CHECK-NEXT: %cond = icmp sgt i64 %n, %idx
+; CHECK-NEXT: br i1 %cond, label %end, label %inner.preheader
+
+; CHECK-LABEL: latch:
+; CHECK-NEXT: %idx.next = add nsw i64 %idx, -1
+; CHECK-NEXT: br label %header
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+ at ptr = external global i64
+
+define dso_local void @hoge() local_unnamed_addr {
+entry:                                            ; preds = %entry
+  %n = sdiv exact i64 undef, 40
+  br label %header
+
+header:                                           ; preds = %latch, %entry
+  %idx = phi i64 [ %idx.next, %latch ], [ undef, %entry ]
+  %cond = icmp sgt i64 %n, %idx
+  br i1 %cond, label %end, label %inner
+
+inner:                                            ; preds = %inner, %header
+  %i = phi i64 [ %i.next, %inner ], [ 0, %header ]
+  %j = phi i64 [ %j.next, %inner ], [ %n, %header ]
+  %i.next = add nsw i64 %i, 1
+  %j.next = add nsw i64 %j, 1
+  store i64 undef, i64* @ptr
+  %cond1 = icmp slt i64 %j, %idx
+  br i1 %cond1, label %inner, label %inner_exit
+
+inner_exit:                                       ; preds = %inner
+  %indvar = phi i64 [ %i.next, %inner ]
+  %indvar_use = add i64 %indvar, 1
+  br label %latch
+
+latch:                                            ; preds = %inner_exit
+  %idx.next = add nsw i64 %idx, -1
+  br label %header
+
+end:                                              ; preds = %header
+  ret void
+}
Index: llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -1869,11 +1869,15 @@
 
   // Now that we're done iterating through lists, clean up any instructions
   // which are now dead.
-  while (!DeadInsts.empty())
-    if (Instruction *Inst =
-            dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val()))
+  while (!DeadInsts.empty()) {
+    Value *V = DeadInsts.pop_back_val();
+
+    if (PHINode *PHI = dyn_cast_or_null<PHINode>(V))
+      Changed |= RecursivelyDeleteDeadPHINode(PHI, TLI, MSSAU.get());
+    else if (Instruction *Inst = dyn_cast_or_null<Instruction>(V))
       Changed |=
           RecursivelyDeleteTriviallyDeadInstructions(Inst, TLI, MSSAU.get());
+  }
 
   // The Rewriter may not be used from this point on.
 


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