[llvm] e83e289 - [SCEVExpander] Forget SCEV when replacing congruent phi.

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2022-11-01T17:49:38Z
New Revision: e83e289fd1aabac9253a04fc8ae6051759ccb20e

URL: https://github.com/llvm/llvm-project/commit/e83e289fd1aabac9253a04fc8ae6051759ccb20e
DIFF: https://github.com/llvm/llvm-project/commit/e83e289fd1aabac9253a04fc8ae6051759ccb20e.diff

LOG: [SCEVExpander] Forget SCEV when replacing congruent phi.

Otherwise there may be stale values left over in the cache, causing a
SCEV verification failure.

Fixes #58702.

Added: 
    llvm/test/Transforms/IndVarSimplify/pr58702-invalidate-scev-when-replacing-congruent-phis.ll

Modified: 
    llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp b/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
index 84db277b2aa1b..29829bc2b5d04 100644
--- a/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
+++ b/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
@@ -1926,6 +1926,7 @@ SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
     if (Value *V = SimplifyPHINode(Phi)) {
       if (V->getType() != Phi->getType())
         continue;
+      SE.forgetValue(Phi);
       Phi->replaceAllUsesWith(V);
       DeadInsts.emplace_back(Phi);
       ++NumElim;

diff  --git a/llvm/test/Transforms/IndVarSimplify/pr58702-invalidate-scev-when-replacing-congruent-phis.ll b/llvm/test/Transforms/IndVarSimplify/pr58702-invalidate-scev-when-replacing-congruent-phis.ll
new file mode 100644
index 0000000000000..e12dd288b624f
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/pr58702-invalidate-scev-when-replacing-congruent-phis.ll
@@ -0,0 +1,59 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes="loop(indvars,loop-deletion,loop-unroll-full)" -verify-scev -S %s | FileCheck %s
+
+define i32 @test(i32 %p_16, i1 %c) {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[OR:%.*]] = or i32 0, [[P_16:%.*]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[OR]], 6
+; CHECK-NEXT:    [[OR_1:%.*]] = or i32 [[XOR]], [[P_16]]
+; CHECK-NEXT:    [[XOR_1:%.*]] = xor i32 [[OR_1]], 6
+; CHECK-NEXT:    [[OR_2:%.*]] = or i32 [[XOR_1]], [[P_16]]
+; CHECK-NEXT:    [[XOR_2:%.*]] = xor i32 [[OR_2]], 6
+; CHECK-NEXT:    br label [[OUTER_HEADER:%.*]]
+; CHECK:       outer.header:
+; CHECK-NEXT:    br label [[INNER_HEADER:%.*]]
+; CHECK:       inner.header:
+; CHECK-NEXT:    br i1 [[C:%.*]], label [[OUTER_LATCH:%.*]], label [[INNER_LATCH:%.*]]
+; CHECK:       inner.latch:
+; CHECK-NEXT:    br i1 [[C]], label [[OUTER_LATCH]], label [[INNER_LATCH_1:%.*]]
+; CHECK:       inner.latch.1:
+; CHECK-NEXT:    br i1 [[C]], label [[OUTER_LATCH]], label [[INNER_LATCH_2:%.*]]
+; CHECK:       inner.latch.2:
+; CHECK-NEXT:    br i1 [[C]], label [[OUTER_LATCH]], label [[INNER_LATCH_3:%.*]]
+; CHECK:       inner.latch.3:
+; CHECK-NEXT:    [[XOR_2_LCSSA:%.*]] = phi i32 [ [[XOR_2]], [[INNER_LATCH_2]] ]
+; CHECK-NEXT:    [[OR_3:%.*]] = or i32 [[XOR_2_LCSSA]], [[P_16]]
+; CHECK-NEXT:    [[XOR_3:%.*]] = xor i32 [[OR_3]], 6
+; CHECK-NEXT:    ret i32 [[XOR_3]]
+; CHECK:       outer.latch:
+; CHECK-NEXT:    br label [[OUTER_HEADER]]
+;
+entry:
+  br label %outer.header
+
+outer.header:
+  %p.1 = phi i32 [ 0, %entry ], [ %p.2.lcssa, %outer.latch ]
+  br label %inner.header
+
+inner.header:
+  %p.2 = phi i32 [ %p.1, %outer.header ], [ %xor, %inner.latch]
+  %p.3 = phi i32 [ 0, %outer.header ], [ %add, %inner.latch ]
+  br i1 %c, label %outer.latch, label %inner.latch
+
+inner.latch:
+  %or = or i32 %p.2, %p_16
+  %xor = xor i32 %or, 6
+  %add = add nuw nsw i32 %p.3, 1
+  %cmp = icmp ult i32 %p.3, 3
+  br i1 %cmp, label %inner.header, label %exit
+
+outer.latch:                                ; preds = %for.body2928
+  %p.2.lcssa = phi i32 [ %p.2, %inner.header ]
+  br label %outer.header
+
+exit:
+  %xor.lcssa = phi i32 [ %xor, %inner.latch ]
+  ret i32 %xor.lcssa
+}
+