[PATCH] D91325: [IndVarSimplify] Drop any stored trip count value before IndVarSimplify

[guopeilin via Phabricator via llvm-commits]

guopeilin created this revision.
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Some nested loops may share the same ExitingBB, so after we finishing FoldExit,
we need to notify OuterLoop and SCEV to drop any stored trip count.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D91325

Files:
  llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
  llvm/test/Transforms/IndVarSimplify/shared-exit-between-nested-loop.ll


Index: llvm/test/Transforms/IndVarSimplify/shared-exit-between-nested-loop.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/IndVarSimplify/shared-exit-between-nested-loop.ll
@@ -0,0 +1,64 @@
+; RUN: opt -indvars -S < %s | FileCheck %s
+
+ at __const.e.f = private unnamed_addr constant <{ <{ [2 x i32], [2 x i32], [8 x [2 x i32]] }>, [10 x [2 x i32]] }> <{ <{ [2 x i32], [2 x i32], [8 x [2 x i32]] }> <{ [2 x i32] [i32 4, i32 8], [2 x i32] [i32 3, i32 10], [8 x [2 x i32]] zeroinitializer }>, [10 x [2 x i32]] [[2 x i32] zeroinitializer, [2 x i32] zeroinitializer, [2 x i32] [i32 1, i32 5], [2 x i32] [i32 2080555007, i32 0], [2 x i32] zeroinitializer, [2 x i32] zeroinitializer, [2 x i32] zeroinitializer, [2 x i32] zeroinitializer, [2 x i32] zeroinitializer, [2 x i32] zeroinitializer] }>, align 4
+
+define dso_local i8 @main() local_unnamed_addr {
+entry:
+  br label %for.cond1.preheader
+
+for.cond1.preheader:                              ; preds = %for.inc15, %entry
+  %storemerge32 = phi i32 [ 0, %entry ], [ %inc16, %for.inc15 ]
+  br label %for.cond4
+
+for.cond4:                                        ; preds = %for.inc, %for.cond1.preheader
+  %storemerge2531 = phi i32 [ 0, %for.cond1.preheader ], [ %inc, %for.inc ]
+  %tobool = icmp eq i32 1, 0
+  br i1 %tobool, label %cleanup, label %if.then
+
+if.then:                                          ; preds = %for.cond4
+; CHECK:        if.then:                                          ; preds = %for.cond4
+; CHECK-NEXT:     br i1 false, label %cleanup, label %for.inc
+  %add = add nuw nsw i32 %storemerge2531, 2
+  %idxprom8 = zext i32 %add to i64
+  %arrayidx10 = getelementptr inbounds <{ <{ [2 x i32], [2 x i32], [8 x [2 x i32]] }>, [10 x [2 x i32]] }>, <{ <{ [2 x i32], [2 x i32], [8 x [2 x i32]] }>, [10 x [2 x i32]] }>* @__const.e.f, i64 0, i32 1, i64 %idxprom8, i64 0
+  %0 = load i32, i32* %arrayidx10, align 4
+  %tobool11 = icmp eq i32 %0, 0
+  br i1 %tobool11, label %cleanup, label %for.inc
+
+for.inc:                                          ; preds = %if.then
+  %inc = add nuw nsw i32 %storemerge2531, 1
+  %cmp2 = icmp ult i32 %inc, 2
+  br i1 %cmp2, label %for.cond4, label %for.inc15
+
+cleanup:                                          ; preds = %if.then, %for.cond4
+  br label %return
+
+for.inc15:                                        ; preds = %for.inc
+; CHECK:        for.inc15:
+; CHECK-NEXT:     %inc16 = add nuw nsw i32 %storemerge32, 1
+; CHECK-NEXT:     %cmp = icmp eq i32 %inc16, 4
+; CHECK-NEXT:     br i1 %cmp, label %for.cond18thread-pre-split, label %for.cond1.preheader
+  %inc16 = add nuw nsw i32 %storemerge32, 1
+  %cmp = icmp eq i32 %inc16, 4
+  br i1 %cmp, label %for.cond18thread-pre-split, label %for.cond1.preheader
+
+for.cond18thread-pre-split:                       ; preds = %for.inc15
+  br i1 1, label %return.loopexit, label %for.inc21.lr.ph
+
+for.inc21.lr.ph:                                  ; preds = %for.cond18thread-pre-split
+  br label %for.inc21
+
+for.inc21:                                        ; preds = %for.inc21, %for.inc21.lr.ph
+  %1 = phi i32 [ undef, %for.inc21.lr.ph ], [ %inc22, %for.inc21 ]
+  %inc22 = add nsw i32 %1, 1
+  br i1 true, label %for.cond18.return.loopexit_crit_edge, label %for.inc21
+
+for.cond18.return.loopexit_crit_edge:             ; preds = %for.inc21
+  br label %return.loopexit
+
+return.loopexit:                                  ; preds = %for.cond18.return.loopexit_crit_edge, %for.cond18thread-pre-split
+  br label %return
+
+return:                                           ; preds = %return.loopexit, %cleanup
+  ret i8 undef
+}
Index: llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -1418,6 +1418,22 @@
     auto *NewCond = ConstantInt::get(OldCond->getType(),
                                      IsTaken ? ExitIfTrue : !ExitIfTrue);
     ReplaceExitCond(BI, NewCond);
+
+    // Some nested loops may share the same ExitingBB. So we need to
+    // forgetTopmostLoop to notify the OuterLoop that the
+    // ExitCount has been changed.
+    Loop *Parent = L->getParentLoop();
+    bool HasSharedExit = false;
+    while (Parent && !HasSharedExit) {
+      SmallVector<BasicBlock *, 16> ParentExitingBlocks;
+      Parent->getExitingBlocks(ParentExitingBlocks);
+      if (std::any_of(ParentExitingBlocks.begin(), ParentExitingBlocks.end(),
+                      [&](BasicBlock *BB) { return BB == ExitingBB; })) {
+        SE->forgetTopmostLoop(Parent);
+        HasSharedExit = true;
+      }
+      Parent = Parent->getParentLoop();
+    }
   };
 
   bool Changed = false;


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