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[LowerSwitch] Fixed faulty PHI node update 

Summary:
When lowerswitch merge several cases into a new default block it's not
updating the PHI nodes accordingly. The code that update the PHI nodes
for the default edge only update the first entry and do not remove the
remaining ones, to make sure the number of entries match the number of
predecessors.

This is easily fixed by replacing the code that update the PHI node with
the already existing utility function for updating PHI nodes.

Reviewers: hans, reames, arsenm

Reviewed By: arsenm

Subscribers: wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D47055

llvm-svn: 332960
This commit is contained in:
Karl-Johan Karlsson 2018-05-22 08:46:48 +00:00
parent cf377a1434
commit 11d68a619e
2 changed files with 66 additions and 10 deletions
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18
llvm/lib/Transforms/Utils/LowerSwitch.cpp
View File

@ -512,25 +512,25 @@ void LowerSwitch::processSwitchInst(SwitchInst *SI,
}
}
unsigned NrOfDefaults = (SI->getDefaultDest() == Default) ? 1 : 0;
for (const auto &Case : SI->cases())
if (Case.getCaseSuccessor() == Default)
NrOfDefaults++;
// Create a new, empty default block so that the new hierarchy of
// if-then statements go to this and the PHI nodes are happy.
BasicBlock *NewDefault = BasicBlock::Create(SI->getContext(), "NewDefault");
F->getBasicBlockList().insert(Default->getIterator(), NewDefault);
BranchInst::Create(Default, NewDefault);
// If there is an entry in any PHI nodes for the default edge, make sure
// to update them as well.
for (BasicBlock::iterator I = Default->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
int BlockIdx = PN->getBasicBlockIndex(OrigBlock);
assert(BlockIdx != -1 && "Switch didn't go to this successor??");
PN->setIncomingBlock((unsigned)BlockIdx, NewDefault);
}
BasicBlock *SwitchBlock =
switchConvert(Cases.begin(), Cases.end(), LowerBound, UpperBound, Val,
OrigBlock, OrigBlock, NewDefault, UnreachableRanges);
// If there are entries in any PHI nodes for the default edge, make sure
// to update them as well.
fixPhis(Default, OrigBlock, NewDefault, NrOfDefaults);
// Branch to our shiny new if-then stuff...
BranchInst::Create(SwitchBlock, OrigBlock);

58
llvm/test/Transforms/Util/lowerswitch.ll
View File

@ -3,7 +3,7 @@
; Test that we don't crash and have a different basic block for each incoming edge.
define void @test0() {
; CHECK-LABEL: @test0
; CHECK: %merge = phi i64 [ 1, %BB3 ], [ 0, %NewDefault ], [ 0, %NodeBlock5 ], [ 0, %LeafBlock1 ]
; CHECK: %merge = phi i64 [ 1, %BB3 ], [ 0, %NodeBlock5 ], [ 0, %LeafBlock1 ], [ 0, %NewDefault ]
BB1:
switch i32 undef, label %BB2 [
i32 3, label %BB2
@ -186,3 +186,59 @@ define void @test2(i32 %mode) {
._crit_edge: ; preds = %34, %0
ret void
}
; Test that the PHI node in for.cond should have one entry for each predecessor
; of its parent basic block after lowerswitch merged several cases into a new
; default block.
define void @test3() {
; CHECK-LABEL: @test3
entry:
br label %lbl1
lbl1: ; preds = %cleanup, %entry
br label %lbl2
lbl2: ; preds = %cleanup, %lbl1
br label %for.cond
for.cond: ; preds = %cleanup, %cleanup, %lbl2
; CHECK: for.cond:
; CHECK: phi i16 [ undef, %lbl2 ], [ %b.3, %NewDefault ]{{$}}
; CHECK: for.cond1:
%b.2 = phi i16 [ undef, %lbl2 ], [ %b.3, %cleanup ], [ %b.3, %cleanup ]
br label %for.cond1
for.cond1: ; preds = %for.inc, %for.cond
%b.3 = phi i16 [ %b.2, %for.cond ], [ undef, %for.inc ]
%tobool = icmp ne i16 %b.3, 0
br i1 %tobool, label %for.body, label %for.end
for.body: ; preds = %for.cond1
br i1 undef, label %if.then, label %for.inc
if.then: ; preds = %for.body
br label %cleanup
for.inc: ; preds = %for.body
br label %for.cond1
for.end: ; preds = %for.cond1
br i1 undef, label %if.then4, label %for.body7
if.then4: ; preds = %for.end
br label %cleanup
for.body7: ; preds = %for.end
br label %cleanup
cleanup: ; preds = %for.body7, %if.then4, %if.then
switch i32 undef, label %unreachable [
i32 0, label %for.cond
i32 2, label %lbl1
i32 5, label %for.cond
i32 3, label %lbl2
]
unreachable: ; preds = %cleanup
unreachable
}