[llvm] 4b6bd1c - [LoopSimplifyCFG] Clear SCEV dispositions when removing dead blocks.

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2022-10-10T18:08:35+01:00
New Revision: 4b6bd1c9d56909b3f25b8dc3ea5b49e0b32d107a

URL: https://github.com/llvm/llvm-project/commit/4b6bd1c9d56909b3f25b8dc3ea5b49e0b32d107a
DIFF: https://github.com/llvm/llvm-project/commit/4b6bd1c9d56909b3f25b8dc3ea5b49e0b32d107a.diff

LOG: [LoopSimplifyCFG] Clear SCEV dispositions when removing dead blocks.

When removing loops & blocks we also need to clear the SCEV dispositions
as they may now contain incorrect values.

Fixes #58262.

Added: 
    llvm/test/Transforms/LoopSimplifyCFG/invalidate-scev-dispositions-2.ll

Modified: 
    llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp b/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
index 686d122ca51a..4348067c9073 100644
--- a/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
@@ -417,6 +417,7 @@ class ConstantTerminatorFoldingImpl {
           DTU.applyUpdates(DTUpdates);
         DTUpdates.clear();
         formLCSSARecursively(*FixLCSSALoop, DT, &LI, &SE);
+        SE.forgetBlockAndLoopDispositions();
       }
     }
 

diff  --git a/llvm/test/Transforms/LoopSimplifyCFG/invalidate-scev-dispositions-2.ll b/llvm/test/Transforms/LoopSimplifyCFG/invalidate-scev-dispositions-2.ll
new file mode 100644
index 000000000000..3d5de47ad001
--- /dev/null
+++ b/llvm/test/Transforms/LoopSimplifyCFG/invalidate-scev-dispositions-2.ll
@@ -0,0 +1,51 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -verify-scev -passes="print<scalar-evolution>,loop-simplifycfg" -S %s 2>&1 | FileCheck %s
+
+; print<scalar-evolution> is used to compute SCEVs for all values & loops in
+; the function
+
+define void @test_pr58262(ptr %src) {
+; CHECK-LABEL: @test_pr58262(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LOOP_1_HEADER:%.*]]
+; CHECK:       loop.1.header.loopexit:
+; CHECK-NEXT:    br label [[LOOP_1_HEADER]]
+; CHECK:       loop.1.header:
+; CHECK-NEXT:    switch i32 0, label [[LOOP_1_HEADER_SPLIT:%.*]] [
+; CHECK-NEXT:    i32 1, label [[LOOP_1_HEADER_LOOPEXIT:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       loop.1.header.split:
+; CHECK-NEXT:    br label [[LOOP_2_HEADER:%.*]]
+; CHECK:       loop.2.header:
+; CHECK-NEXT:    call void @clobber()
+; CHECK-NEXT:    [[L:%.*]] = load i16, ptr [[SRC:%.*]], align 1
+; CHECK-NEXT:    [[C:%.*]] = icmp ult i16 0, [[L]]
+; CHECK-NEXT:    br i1 [[C]], label [[TRAP:%.*]], label [[LOOP_2_LATCH:%.*]]
+; CHECK:       loop.2.latch:
+; CHECK-NEXT:    br label [[LOOP_2_HEADER]]
+; CHECK:       trap:
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %loop.1.header
+
+loop.1.header:
+  br label %loop.2.header
+
+loop.2.header:
+  br i1 true, label %then, label %loop.1.header
+
+then:
+  call void @clobber()
+  %l = load i16, ptr %src, align 1
+  %c = icmp ult i16 0, %l
+  br i1 %c, label %trap, label %loop.2.latch
+
+loop.2.latch:
+  br label %loop.2.header
+
+trap:                                             ; preds = %for.body
+  ret void
+}
+
+declare void @clobber()