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SimplifyCFG: Correctly handle switch lookup tables which fully cover the input type and use bit tests to check for holes

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When using bit tests for hole checks, we call AddPredecessorToBlock to give the
phi node a value from the bit test block. This would break if we've
previously called removePredecessor on the default destination because the
switch is fully covered.

Test case by Mark Lacey.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235771 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hans Wennborg 2015-04-24 20:57:56 +00:00
parent af8df399e1
commit 7a301c1b8c
2 changed files with 38 additions and 4 deletions
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13
lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -4159,10 +4159,8 @@ static bool SwitchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
if (!DefaultIsReachable || GeneratingCoveredLookupTable) {
Builder.CreateBr(LookupBB);
// We cached PHINodes in PHIs, to avoid accessing deleted PHINodes later,
// do not delete PHINodes here.
SI->getDefaultDest()->removePredecessor(SI->getParent(),
/*DontDeleteUselessPHIs=*/true);
// Note: We call removeProdecessor later since we need to be able to get the
// PHI value for the default case in case we're using a bit mask.
} else {
Value *Cmp = Builder.CreateICmpULT(TableIndex, ConstantInt::get(
MinCaseVal->getType(), TableSize));
@ -4214,6 +4212,13 @@ static bool SwitchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
AddPredecessorToBlock(SI->getDefaultDest(), MaskBB, SI->getParent());
}
if (!DefaultIsReachable || GeneratingCoveredLookupTable) {
// We cached PHINodes in PHIs, to avoid accessing deleted PHINodes later,
// do not delete PHINodes here.
SI->getDefaultDest()->removePredecessor(SI->getParent(),
/*DontDeleteUselessPHIs=*/true);
}
bool ReturnedEarly = false;
for (size_t I = 0, E = PHIs.size(); I != E; ++I) {
PHINode *PHI = PHIs[I];

29
test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
View File

@ -1273,3 +1273,32 @@ end:
; CHECK-LABEL: @pr20210
; CHECK: switch i8 %x
}
; Make sure we do not crash due to trying to generate an unguarded
; lookup (since i3 can only hold values in the range of explicit
; values) and simultaneously trying to generate a branch to deal with
; the fact that we have holes in the range.
define i32 @covered_switch_with_bit_tests(i3) {
entry:
switch i3 %0, label %l6 [
i3 -3, label %l5
i3 -4, label %l5
i3 3, label %l1
i3 2, label %l1
]
l1: br label %l2
l2:
%x = phi i32 [ 1, %l1 ], [ 2, %l5 ]
br label %l6
l5: br label %l2
l6:
%r = phi i32 [ %x, %l2 ], [ 0, %entry ]
ret i32 %r
; CHECK-LABEL: @covered_switch_with_bit_tests
; CHECK: entry
; CHECK-NEXT: switch
}