PR9446: RecursivelyDeleteTriviallyDeadInstructions can delete the instruction

after the given instruction; make sure to handle that case correctly.
(It's difficult to trigger; the included testcase involves a dead
block, but I don't think that's a requirement.)

While I'm here, get rid of the unnecessary warning about
SimplifyInstructionsInBlock, since it should work correctly as far as I know.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128782 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Transforms/Utils/Local.h b/include/llvm/Transforms/Utils/Local.h
index f63796c4eab5a4dea6d515e4be498555a1517990..e61dcb347c85d24dae1aafaaba35c64ea6f0fb93 100644 (file)
--- a/include/llvm/Transforms/Utils/Local.h
+++ b/include/llvm/Transforms/Utils/Local.h
@@ -74,10 +74,6 @@ bool RecursivelyDeleteDeadPHINode(PHINode *PN);
 ///
 /// This returns true if it changed the code, note that it can delete
 /// instructions in other blocks as well in this block.
-///
-/// WARNING: Do not use this function on unreachable blocks, as recursive
-/// simplification is not able to handle corner-case scenarios that can
-/// arise in them.
 bool SimplifyInstructionsInBlock(BasicBlock *BB, const TargetData *TD = 0);
     
 //===----------------------------------------------------------------------===//

diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index 47ef1c91749ce3a451d4ac7dd3749435403d00f3..26ae295d5dc0c94da5c5e4283a1046154737dcf6 100644 (file)
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -332,8 +332,11 @@ bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, const TargetData *TD) {
         BI = BB->begin();
       continue;
     }
-    
+
+    WeakVH BIHandle(BI);
     MadeChange |= RecursivelyDeleteTriviallyDeadInstructions(Inst);
+    if (BIHandle != BI)
+      BI = BB->begin();
   }
   return MadeChange;
 }

diff --git a/test/Transforms/JumpThreading/2011-04-02-SimplifyDeadBlock.ll b/test/Transforms/JumpThreading/2011-04-02-SimplifyDeadBlock.ll
new file mode 100644 (file)
index 0000000..76dd2d1
--- /dev/null
+++ b/test/Transforms/JumpThreading/2011-04-02-SimplifyDeadBlock.ll
@@ -0,0 +1,32 @@
+; RUN: opt < %s -jump-threading
+; PR9446
+; Just check that it doesn't crash
+
+define void @int327() nounwind {
+entry:
+  unreachable
+
+for.cond:                                         ; preds = %for.cond4
+  %tobool3 = icmp eq i8 undef, 0
+  br i1 %tobool3, label %for.cond23, label %for.cond4
+
+for.cond4:                                        ; preds = %for.cond
+  br label %for.cond
+
+for.cond23:                                       ; preds = %for.body28, %for.cond23, %for.cond
+  %conv321 = phi i32 [ %conv32, %for.body28 ], [ 0, %for.cond ], [ %conv321, %for.cond23 ]
+  %l_266.0 = phi i32 [ %phitmp, %for.body28 ], [ 0, %for.cond ], [ 0, %for.cond23 ]
+  %cmp26 = icmp eq i32 %l_266.0, 0
+  br i1 %cmp26, label %for.body28, label %for.cond23
+
+for.body28:                                       ; preds = %for.cond23
+  %and = and i32 %conv321, 1
+  %conv32 = zext i8 undef to i32
+  %add = add nsw i32 %l_266.0, 1
+  %phitmp = and i32 %add, 255
+  br label %for.cond23
+
+if.end43:                                         ; No predecessors!
+  ret void
+}
+