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

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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
This commit is contained in:
Bob Wilson 2009-05-12 03:48:10 +00:00
parent 81db61a2e6
commit 74b0ccc577
2 changed files with 33 additions and 3 deletions
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6
lib/CodeGen/CodePlacementOpt.cpp
View File

@ -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;
}
}

30
test/CodeGen/ARM/2009-05-11-CodePlacementCrash.ll Normal file
View File

@ -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