[PATCH] D32126: [CodeGenPrepare] Fix crash due to an invalid CFG

[Brendon Cahoon via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL300480: [CodeGenPrepare] Fix crash due to an invalid CFG (authored by bcahoon).

Changed prior to commit:
  https://reviews.llvm.org/D32126?vs=95447&id=95472#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D32126

Files:
  llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
  llvm/trunk/test/Transforms/CodeGenPrepare/split-indirect-loop.ll


Index: llvm/trunk/test/Transforms/CodeGenPrepare/split-indirect-loop.ll
===================================================================
--- llvm/trunk/test/Transforms/CodeGenPrepare/split-indirect-loop.ll
+++ llvm/trunk/test/Transforms/CodeGenPrepare/split-indirect-loop.ll
@@ -0,0 +1,37 @@
+; RUN: opt -codegenprepare -S < %s | FileCheck %s
+
+; Test that an invalid CFG is not created by splitIndirectCriticalEdges
+; transformation when the 'target' block is a loop to itself.
+
+; CHECK: .split:
+; CHECK: br label %while.body.clone
+; CHECK: if.else1:
+; CHECK: indirectbr
+; CHECK: while.body.clone:
+; CHECK: br label %.split
+
+define void @test() {
+entry:
+  br label %if.else
+
+if.else:
+  br i1 undef, label %while.body, label %preheader
+
+preheader:
+  br label %if.else1
+
+if.then:
+  unreachable
+
+while.body:
+  %dest.sroa = phi i32 [ %1, %while.body ], [ undef, %if.else1 ], [ undef, %if.else ]
+  %0 = inttoptr i32 %dest.sroa to i8*
+  %incdec.ptr = getelementptr inbounds i8, i8* %0, i32 -1
+  %1 = ptrtoint i8* %incdec.ptr to i32
+  store i8 undef, i8* %incdec.ptr, align 1
+  br label %while.body
+
+if.else1:
+  indirectbr i8* undef, [label %if.then, label %while.body, label %if.else, label %if.else1]
+}
+
Index: llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
+++ llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
@@ -570,8 +570,14 @@
     ValueToValueMapTy VMap;
     BasicBlock *DirectSucc = CloneBasicBlock(Target, VMap, ".clone", &F);
 
-    for (BasicBlock *Pred : OtherPreds)
-      Pred->getTerminator()->replaceUsesOfWith(Target, DirectSucc);
+    for (BasicBlock *Pred : OtherPreds) {
+      // If the target is a loop to itself, then the terminator of the split
+      // block needs to be updated.
+      if (Pred == Target)
+        BodyBlock->getTerminator()->replaceUsesOfWith(Target, DirectSucc);
+      else
+        Pred->getTerminator()->replaceUsesOfWith(Target, DirectSucc);
+    }
 
     // Ok, now fix up the PHIs. We know the two blocks only have PHIs, and that
     // they are clones, so the number of PHIs are the same.


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