Fix pr4195: When iterating through predecessor blocks, break out of the loop

after finding the (unique) layout predecessor.  Sometimes a block may be listed
more than once, and processing it more than once in this loop can lead to
inconsistent values for FtTBB/FtFBB, since the AnalyzeBranch method does not
clear these values.  There's no point in continuing the loop regardless.
The testcase for this is reduced from the 2003-05-02-DependentPHI SingleSource
test.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71536 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 33 insertions, 3 deletions

diff --git a/lib/CodeGen/CodePlacementOpt.cpp b/lib/CodeGen/CodePlacementOpt.cpp
index 77d23eed6c..2e1d12d234 100644
--- a/lib/CodeGen/CodePlacementOpt.cpp
+++ b/lib/CodeGen/CodePlacementOpt.cpp
@@ -155,10 +155,10 @@ bool CodePlacementOpt::OptimizeIntraLoopEdges() {
         // A fallthrough.
         FtMBB = PredMBB;
         MachineLoop *PL = MLI->getLoopFor(PredMBB);
-        if (PL && (PL == L || PL->getLoopDepth() >= L->getLoopDepth())) {
+        if (PL && (PL == L || PL->getLoopDepth() >= L->getLoopDepth()))
           OkToMove = false;
-          break;
-        }
+
+        break;
       }
     }
 
diff --git a/test/CodeGen/ARM/2009-05-11-CodePlacementCrash.ll b/test/CodeGen/ARM/2009-05-11-CodePlacementCrash.ll
new file mode 100644
index 0000000000..35d4306e9d
--- /dev/null
+++ b/test/CodeGen/ARM/2009-05-11-CodePlacementCrash.ll
@@ -0,0 +1,30 @@
+; RUN: llvm-as < %s | llc -march=arm
+	%struct.List = type { %struct.List*, i32 }
+@Node5 = external constant %struct.List		; <%struct.List*> [#uses=1]
+@"\01LC" = external constant [7 x i8]		; <[7 x i8]*> [#uses=1]
+
+define i32 @main() nounwind {
+entry:
+	br label %bb
+
+bb:		; preds = %bb3, %entry
+	%CurL.02 = phi %struct.List* [ @Node5, %entry ], [ %2, %bb3 ]		; <%struct.List*> [#uses=1]
+	%PrevL.01 = phi %struct.List* [ null, %entry ], [ %CurL.02, %bb3 ]		; <%struct.List*> [#uses=1]
+	%0 = icmp eq %struct.List* %PrevL.01, null		; <i1> [#uses=1]
+	br i1 %0, label %bb3, label %bb1
+
+bb1:		; preds = %bb
+	br label %bb3
+
+bb3:		; preds = %bb1, %bb
+	%iftmp.0.0 = phi i32 [ 0, %bb1 ], [ -1, %bb ]		; <i32> [#uses=1]
+	%1 = tail call i32 (i8*, ...)* @printf(i8* getelementptr ([7 x i8]* @"\01LC", i32 0, i32 0), i32 0, i32 %iftmp.0.0) nounwind		; <i32> [#uses=0]
+	%2 = load %struct.List** null, align 4		; <%struct.List*> [#uses=2]
+	%phitmp = icmp eq %struct.List* %2, null		; <i1> [#uses=1]
+	br i1 %phitmp, label %bb5, label %bb
+
+bb5:		; preds = %bb3
+	ret i32 0
+}
+
+declare i32 @printf(i8* nocapture, ...) nounwind