[PATCH] D137651: [LoopFlatten] Forget SCEV value for removed incomming values of phi

[luxufan via Phabricator via llvm-commits]

StephenFan created this revision.
StephenFan added reviewers: nikic, fhahn.
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Fixes: https://github.com/llvm/llvm-project/issues/58865


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D137651

Files:
  llvm/lib/Transforms/Scalar/LoopFlatten.cpp
  llvm/test/Transforms/LoopFlatten/pr58865.ll


Index: llvm/test/Transforms/LoopFlatten/pr58865.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LoopFlatten/pr58865.ll
@@ -0,0 +1,28 @@
+; RUN: opt -loop-flatten -verify-scev < %s
+
+define void @sum_2d(ptr %p) {
+entry:
+  br label %outer
+
+outer:                                         ; preds = %outer.latch, %entry
+  %sum.04 = phi i16 [ 0, %entry ], [ %0, %outer.latch ]
+  %outer.iv = phi i16 [ 0, %entry ], [ %outer.iv.next, %outer.latch ]
+  br label %inner
+
+inner:                                        ; preds = %inner, %outer
+  %sum.12 = phi i16 [ %sum.04, %outer ], [ %0, %inner ]
+  %inner.iv = phi i16 [ 0, %outer ], [ %inner.iv.next, %inner ]
+  %0 = load i16, ptr %p, align 1
+  %inner.iv.next = add nsw i16 %inner.iv, 1
+  %cmp2 = icmp slt i16 %inner.iv, 0
+  br i1 %cmp2, label %inner, label %outer.latch
+
+outer.latch:                                         ; preds = %inner
+  %outer.iv.next = add nsw i16 %outer.iv, 1
+  %cmp = icmp slt i16 %outer.iv.next, 0
+  br i1 %cmp, label %outer, label %exit
+
+exit:                                         ; preds = %outer.latch
+  ret void
+
+}
Index: llvm/lib/Transforms/Scalar/LoopFlatten.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopFlatten.cpp
+++ llvm/lib/Transforms/Scalar/LoopFlatten.cpp
@@ -722,12 +722,13 @@
 
   // Fix up PHI nodes that take values from the inner loop back-edge, which
   // we are about to remove.
-  FI.InnerInductionPHI->removeIncomingValue(FI.InnerLoop->getLoopLatch());
+  SE->forgetValue(
+      FI.InnerInductionPHI->removeIncomingValue(FI.InnerLoop->getLoopLatch()));
 
   // The old Phi will be optimised away later, but for now we can't leave
   // leave it in an invalid state, so are updating them too.
   for (PHINode *PHI : FI.InnerPHIsToTransform)
-    PHI->removeIncomingValue(FI.InnerLoop->getLoopLatch());
+    SE->forgetValue(PHI->removeIncomingValue(FI.InnerLoop->getLoopLatch()));
 
   // Modify the trip count of the outer loop to be the product of the two
   // trip counts.


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