[PATCH] D87392: [JumpThreading] Fix an incorrect Modified status

[David Stenberg via Phabricator via llvm-commits]

dstenb updated this revision to Diff 290894.
dstenb edited the summary of this revision.
dstenb added a comment.

Continue using a bool return instead of a tri-state.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D87392/new/

https://reviews.llvm.org/D87392

Files:
  llvm/lib/Transforms/Scalar/JumpThreading.cpp
  llvm/test/Transforms/JumpThreading/constant-fold-status.ll


Index: llvm/test/Transforms/JumpThreading/constant-fold-status.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/JumpThreading/constant-fold-status.ll
@@ -0,0 +1,28 @@
+; RUN: opt -jump-threading < %s -S -o - | FileCheck %s
+
+; Reproducer for PR47297.
+
+; The pass did previously not report a correct Modified status in the case
+; where a terminator's condition was successfully constant folded, but there
+; were no other transformations done. This was caught by the pass return
+; status check that is hidden under EXPENSIVE_CHECKS.
+
+; CHECK-LABEL: entry:
+; CHECK-NEXT: br i1 icmp eq (i32 ptrtoint (i16* @a to i32), i32 0), label %overflow, label %cont
+
+ at a = internal global i16 0
+
+define void @foo(i16 %d) {
+entry:
+  %.not = icmp eq i16 zext (i1 icmp ne (i32 ptrtoint (i16* @a to i32), i32 0) to i16), 0
+  br i1 %.not, label %overflow, label %cont
+
+overflow:                                         ; preds = %entry
+  call void @bar()
+  br label %cont
+
+cont:                                             ; preds = %overflow, %entry
+  ret void
+}
+
+declare void @bar()
Index: llvm/lib/Transforms/Scalar/JumpThreading.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -1040,6 +1040,9 @@
     return false; // Must be an invoke or callbr.
   }
 
+  // Keep track if we constant folded the condition in this invocation.
+  bool ConstantFolded = false;
+
   // Run constant folding to see if we can reduce the condition to a simple
   // constant.
   if (Instruction *I = dyn_cast<Instruction>(Condition)) {
@@ -1050,6 +1053,7 @@
       if (isInstructionTriviallyDead(I, TLI))
         I->eraseFromParent();
       Condition = SimpleVal;
+      ConstantFolded = true;
     }
   }
 
@@ -1100,7 +1104,7 @@
     // FIXME: Unify this with code below.
     if (ProcessThreadableEdges(Condition, BB, Preference, Terminator))
       return true;
-    return false;
+    return ConstantFolded;
   }
 
   if (CmpInst *CondCmp = dyn_cast<CmpInst>(CondInst)) {


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