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

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.

Reviewers: sanjoy, mkazantsev

Reviewed By: mkazantsev

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58192

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354031 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Utils/LoopUnrollPeel.cpp b/lib/Transforms/Utils/LoopUnrollPeel.cpp
index f893921aca35a03fbd9a2fa74ea8d3be74feefab..fca05b7b6f2ba641caf1c7cc428297a927578914 100644 (file)
--- a/lib/Transforms/Utils/LoopUnrollPeel.cpp
+++ b/lib/Transforms/Utils/LoopUnrollPeel.cpp
@@ -664,16 +664,14 @@ bool llvm::peelLoop(Loop *L, unsigned PeelCount, LoopInfo *LI,
     LatchBR->setMetadata(LLVMContext::MD_prof, WeightNode);
   }
 
-  // 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;
+
+  // We modified the loop, update SE.
+  SE->forgetTopmostLoop(L);
+
+  // FIXME: Incrementally update loop-simplify
+  simplifyLoop(L, DT, LI, SE, AC, PreserveLCSSA);
 
   NumPeeled++;
 

diff --git a/test/Transforms/LoopUnroll/peel-loop-scev-invalidate.ll b/test/Transforms/LoopUnroll/peel-loop-scev-invalidate.ll
new file mode 100644 (file)
index 0000000..c44da31
--- /dev/null
+++ b/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
+}