[llvm] 562521e - [LoopBoundSplit] Update phi node in exit block

[Jingu Kang via llvm-commits]

Author: Jingu Kang
Date: 2021-09-03T09:10:50+01:00
New Revision: 562521e2d15aff38587aef8c6ea1baf3ed87513c

URL: https://github.com/llvm/llvm-project/commit/562521e2d15aff38587aef8c6ea1baf3ed87513c
DIFF: https://github.com/llvm/llvm-project/commit/562521e2d15aff38587aef8c6ea1baf3ed87513c.diff

LOG: [LoopBoundSplit] Update phi node in exit block

It fixes https://bugs.llvm.org/show_bug.cgi?id=51700

Differential Revision:

Added: 
    llvm/test/Transforms/LoopBoundSplit/bug-loop-bound-split-phi-in-exit-block.ll

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/LoopBoundSplit.cpp b/llvm/lib/Transforms/Scalar/LoopBoundSplit.cpp
index 993b154dc9a8c..a89f0aa9e9e7d 100644
--- a/llvm/lib/Transforms/Scalar/LoopBoundSplit.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopBoundSplit.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/Scalar/LoopBoundSplit.h"
+#include "llvm/ADT/Sequence.h"
 #include "llvm/Analysis/LoopAccessAnalysis.h"
 #include "llvm/Analysis/LoopAnalysisManager.h"
 #include "llvm/Analysis/LoopInfo.h"
@@ -398,6 +399,20 @@ static bool splitLoopBound(Loop &L, DominatorTree &DT, LoopInfo &LI,
   else
     ExitingCond.BI->setSuccessor(1, PostLoopPreHeader);
 
+  // Update phi node in exit block of post-loop.
+  for (PHINode &PN : PostLoop->getExitBlock()->phis()) {
+    for (auto i : seq<int>(0, PN.getNumOperands())) {
+      // Check incoming block is pre-loop's exiting block.
+      if (PN.getIncomingBlock(i) == L.getExitingBlock()) {
+        // Replace pre-loop's exiting block by post-loop's preheader.
+        PN.setIncomingBlock(i, PostLoopPreHeader);
+        // Add a new incoming value with post-loop's exiting block.
+        PN.addIncoming(VMap[PN.getIncomingValue(i)],
+                       PostLoop->getExitingBlock());
+      }
+    }
+  }
+
   // Update dominator tree.
   DT.changeImmediateDominator(PostLoopPreHeader, L.getExitingBlock());
   DT.changeImmediateDominator(PostLoop->getExitBlock(), PostLoopPreHeader);

diff  --git a/llvm/test/Transforms/LoopBoundSplit/bug-loop-bound-split-phi-in-exit-block.ll b/llvm/test/Transforms/LoopBoundSplit/bug-loop-bound-split-phi-in-exit-block.ll
new file mode 100644
index 0000000000000..594919c2c82d4
--- /dev/null
+++ b/llvm/test/Transforms/LoopBoundSplit/bug-loop-bound-split-phi-in-exit-block.ll
@@ -0,0 +1,77 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes=loop-bound-split -S < %s | FileCheck %s
+
+; Previously, it caused compiler crash from verifier.
+; The phi node in exit block should be updated properly.
+
+define i16 @test_int() {
+; CHECK-LABEL: @test_int(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[ENTRY_SPLIT:%.*]]
+; CHECK:       entry.split:
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[I:%.*]] = phi i16 [ 0, [[ENTRY_SPLIT]] ], [ [[ADD:%.*]], [[COND_END:%.*]] ]
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp ult i16 [[I]], 3
+; CHECK-NEXT:    br i1 true, label [[COND_TRUE:%.*]], label [[COND_FALSE:%.*]]
+; CHECK:       cond.true:
+; CHECK-NEXT:    br label [[COND_END]]
+; CHECK:       cond.false:
+; CHECK-NEXT:    br label [[COND_END]]
+; CHECK:       cond.end:
+; CHECK-NEXT:    [[CALL:%.*]] = call i16 @foo()
+; CHECK-NEXT:    [[ADD]] = add nuw nsw i16 [[I]], 1
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp ult i16 [[I]], 3
+; CHECK-NEXT:    br i1 [[CMP2]], label [[FOR_BODY]], label [[ENTRY_SPLIT_SPLIT:%.*]]
+; CHECK:       entry.split.split:
+; CHECK-NEXT:    [[CALL_LCSSA1:%.*]] = phi i16 [ [[CALL]], [[COND_END]] ]
+; CHECK-NEXT:    [[I_LCSSA:%.*]] = phi i16 [ [[I]], [[COND_END]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = icmp ne i16 [[I_LCSSA]], 11
+; CHECK-NEXT:    br i1 [[TMP0]], label [[FOR_BODY_SPLIT_PREHEADER:%.*]], label [[END:%.*]]
+; CHECK:       for.body.split.preheader:
+; CHECK-NEXT:    br label [[FOR_BODY_SPLIT:%.*]]
+; CHECK:       for.body.split:
+; CHECK-NEXT:    [[I_SPLIT:%.*]] = phi i16 [ [[ADD_SPLIT:%.*]], [[COND_END_SPLIT:%.*]] ], [ 0, [[FOR_BODY_SPLIT_PREHEADER]] ]
+; CHECK-NEXT:    [[CMP1_SPLIT:%.*]] = icmp ult i16 [[I_SPLIT]], 3
+; CHECK-NEXT:    br i1 false, label [[COND_TRUE_SPLIT:%.*]], label [[COND_FALSE_SPLIT:%.*]]
+; CHECK:       cond.false.split:
+; CHECK-NEXT:    br label [[COND_END_SPLIT]]
+; CHECK:       cond.true.split:
+; CHECK-NEXT:    br label [[COND_END_SPLIT]]
+; CHECK:       cond.end.split:
+; CHECK-NEXT:    [[CALL_SPLIT:%.*]] = call i16 @foo()
+; CHECK-NEXT:    [[ADD_SPLIT]] = add nuw nsw i16 [[I_SPLIT]], 1
+; CHECK-NEXT:    [[CMP2_SPLIT:%.*]] = icmp ult i16 [[I_SPLIT]], 11
+; CHECK-NEXT:    br i1 [[CMP2_SPLIT]], label [[FOR_BODY_SPLIT]], label [[END_LOOPEXIT:%.*]]
+; CHECK:       end.loopexit:
+; CHECK-NEXT:    [[CALL_LCSSA_PH:%.*]] = phi i16 [ [[CALL_SPLIT]], [[COND_END_SPLIT]] ]
+; CHECK-NEXT:    br label [[END]]
+; CHECK:       end:
+; CHECK-NEXT:    [[CALL_LCSSA:%.*]] = phi i16 [ [[CALL_LCSSA1]], [[ENTRY_SPLIT_SPLIT]] ], [ [[CALL_LCSSA_PH]], [[END_LOOPEXIT]] ]
+; CHECK-NEXT:    ret i16 [[CALL_LCSSA]]
+;
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %cond.end
+  %i = phi i16 [ 0, %entry ], [ %add, %cond.end ]
+  %cmp1 = icmp ult i16 %i, 3
+  br i1 %cmp1, label %cond.true, label %cond.false
+
+cond.true:                                        ; preds = %for.body
+  br label %cond.end
+
+cond.false:                                       ; preds = %for.body
+  br label %cond.end
+
+cond.end:                                         ; preds = %cond.false, %cond.true
+  %call = call i16 @foo()
+  %add = add nuw nsw i16 %i, 1
+  %cmp2 = icmp ult i16 %i, 11
+  br i1 %cmp2, label %for.body, label %end
+
+end:                                              ; preds = %cond.end
+  ret i16 %call
+}
+
+declare i16 @foo()