[PATCH] D58192: [LoopUnrollPeel] Add case where we should forget the peeled loop from SCEV.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: sanjoy, mkazantsev.
Herald added subscribers: dmgreen, javed.absar, zzheng, hiraditya.
Herald added a project: LLVM.

The test case requires the peeled loop to be forgotten after peeling,
even though it does not have a parent. When called via the unroller,
SE->forgetTopmostLoop is also called, so the test case would also pass
without any SCEV invalidation, but peelLoop is exposed as utility
function. Also, in the test case, simplifyLoop will make changes,
removing the loop from SCEV, but it is better to not rely on this
behavior.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D58192

Files:
  llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
  llvm/test/Transforms/LoopUnroll/peel-loop-scev-invalidate.ll


Index: llvm/test/Transforms/LoopUnroll/peel-loop-scev-invalidate.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LoopUnroll/peel-loop-scev-invalidate.ll
@@ -0,0 +1,42 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -S -loop-unroll -unroll-force-peel-count=1 -verify-scev -verify-dom-info | FileCheck %s
+
+
+define void @test1(i32 %k) {
+; CHECK-LABEL: @test1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL_BEGIN:%.*]]
+; CHECK:       for.body.peel.begin:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL:%.*]]
+; CHECK:       for.body.peel:
+; CHECK-NEXT:    [[INC_PEEL:%.*]] = add nsw i32 0, 1
+; CHECK-NEXT:    [[CMP_PEEL:%.*]] = icmp ult i32 0, [[K:%.*]]
+; CHECK-NEXT:    br i1 [[CMP_PEEL]], label [[FOR_BODY_PEEL_NEXT:%.*]], label [[FOR_END:%.*]]
+; CHECK:       for.body.peel.next:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL_NEXT1:%.*]]
+; CHECK:       for.body.peel.next1:
+; CHECK-NEXT:    br label [[ENTRY_PEEL_NEWPH:%.*]]
+; CHECK:       entry.peel.newph:
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[I_05:%.*]] = phi i32 [ [[INC_PEEL]], [[ENTRY_PEEL_NEWPH]] ], [ [[INC:%.*]], [[FOR_BODY]] ]
+; CHECK-NEXT:    [[INC]] = add nuw nsw i32 [[I_05]], 1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i32 [[I_05]], [[K]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END_LOOPEXIT:%.*]], !llvm.loop !0
+; CHECK:       for.end.loopexit:
+; CHECK-NEXT:    br label [[FOR_END]]
+; CHECK:       for.end:
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %for.body
+
+for.body:
+  %i.05 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %inc = add nsw i32 %i.05, 1
+  %cmp = icmp ult i32 %i.05, %k
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:
+  ret void
+}
Index: llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
===================================================================
--- llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
+++ llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
@@ -665,15 +665,12 @@
   }
 
   // If the loop is nested, we changed the parent loop, update SE.
-  if (Loop *ParentLoop = L->getParentLoop()) {
-    SE->forgetLoop(ParentLoop);
-
-    // FIXME: Incrementally update loop-simplify
-    simplifyLoop(ParentLoop, DT, LI, SE, AC, PreserveLCSSA);
-  } else {
-    // FIXME: Incrementally update loop-simplify
-    simplifyLoop(L, DT, LI, SE, AC, PreserveLCSSA);
-  }
+  if (Loop *ParentLoop = L->getParentLoop())
+    L = ParentLoop;
+
+  SE->forgetLoop(L);
+  // FIXME: Incrementally update loop-simplify
+  simplifyLoop(L, DT, LI, SE, AC, PreserveLCSSA);
 
   NumPeeled++;
 


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