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PR9446: RecursivelyDeleteTriviallyDeadInstructions can delete the instruction

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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
This commit is contained in:
Eli Friedman 2011-04-02 22:45:17 +00:00
parent 6bdd261df9
commit 71ad2c9eda
3 changed files with 36 additions and 5 deletions
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4
include/llvm/Transforms/Utils/Local.h
View File

@ -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);
//===----------------------------------------------------------------------===//

5
lib/Transforms/Utils/Local.cpp
View File

@ -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;
}

32
test/Transforms/JumpThreading/2011-04-02-SimplifyDeadBlock.ll Normal file
View File

@ -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
}