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Fix the predecessor removal logic in r193045.

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Additionally some small comment/stylistic fixes are included as well.

llvm-svn: 193068
This commit is contained in:
Michael Gottesman 2013-10-21 05:20:11 +00:00
parent ab46af5515
commit 80054d1ccd
1 changed files with 9 additions and 11 deletions
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20
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -3741,18 +3741,20 @@ static bool SwitchToLookupTable(SwitchInst *SI,
// Compute the maximum table size representable by the integer type we are
// switching upon.
const unsigned CaseSize = MinCaseVal->getType()->getPrimitiveSizeInBits();
const uint64_t MaxTableSize = CaseSize > 63? UINT64_MAX : 1ULL << CaseSize;
unsigned CaseSize = MinCaseVal->getType()->getPrimitiveSizeInBits();
uint64_t MaxTableSize = CaseSize > 63? UINT64_MAX : 1ULL << CaseSize;
assert(MaxTableSize >= TableSize &&
"It is impossible for a switch to have more entries than the max "
"representable value of its input integer type's size.");
// If we have a covered lookup table, unconditionally branch to the lookup table
// BB. Otherwise, check if the condition value is within the case range. If it
// is so, branch to the new BB. Otherwise branch to SI's default destination.
// If we have a fully covered lookup table, unconditionally branch to the
// lookup table BB. Otherwise, check if the condition value is within the case
// range. If it is so, branch to the new BB. Otherwise branch to SI's default
// destination.
const bool GeneratingCoveredLookupTable = MaxTableSize == TableSize;
if (GeneratingCoveredLookupTable) {
Builder.CreateBr(LookupBB);
SI->getDefaultDest()->removePredecessor(SI->getParent());
} else {
Value *Cmp = Builder.CreateICmpULT(TableIndex, ConstantInt::get(
MinCaseVal->getType(), TableSize));
@ -3786,14 +3788,10 @@ static bool SwitchToLookupTable(SwitchInst *SI,
Builder.CreateBr(CommonDest);
// Remove the switch.
for (unsigned i = 0; i < SI->getNumSuccessors(); ++i) {
for (unsigned i = 0, e = SI->getNumSuccessors(); i < e; ++i) {
BasicBlock *Succ = SI->getSuccessor(i);
// If we are not generating a covered lookup table, we will have a
// conditional branch from SI's parent BB to SI's default destination if our
// input value lies outside of our case range. Thus in that case leave the
// default destination BB as a predecessor of SI's parent BB.
if (Succ == SI->getDefaultDest() && !GeneratingCoveredLookupTable)
if (Succ == SI->getDefaultDest())
continue;
Succ->removePredecessor(SI->getParent());
}