[PATCH] D146903: (WIP)[SimplifyCFG] add nsw on SwitchToLookupTable index calculation outside of BuildLookup
Kohei Asano via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Wed May 17 06:57:43 PDT 2023
khei4 updated this revision to Diff 523037.
khei4 added a comment.
temporary remove changes in BuildLookup
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D146903/new/
https://reviews.llvm.org/D146903
Files:
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
Index: llvm/lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -6471,6 +6471,21 @@
std::vector<DominatorTree::UpdateType> Updates;
+ // Compute the maximum table size representable by the integer type we are
+ // switching upon.
+ 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 the default destination is unreachable, or if the lookup table covers
+ // all values of the conditional variable, branch directly to the lookup table
+ // BB. Otherwise, check that the condition is within the case range.
+ const bool DefaultIsReachable =
+ !isa<UnreachableInst>(SI->getDefaultDest()->getFirstNonPHIOrDbg());
+ const bool GeneratingCoveredLookupTable = (MaxTableSize == TableSize);
+
// Create the BB that does the lookups.
Module &Mod = *CommonDest->getParent()->getParent();
BasicBlock *LookupBB = BasicBlock::Create(
@@ -6485,24 +6500,13 @@
TableIndex = SI->getCondition();
} else {
TableIndexOffset = MinCaseVal;
- TableIndex =
- Builder.CreateSub(SI->getCondition(), TableIndexOffset, "switch.tableidx");
+ // If the default is unreachable, all case values are s>= MinCaseVal, so the
+ // subtraction cannot wrap in a signed sense.
+ TableIndex = Builder.CreateSub(SI->getCondition(), TableIndexOffset,
+ "switch.tableidx", /*HasNUW =*/false,
+ /*HasNSW =*/!DefaultIsReachable);
}
- // Compute the maximum table size representable by the integer type we are
- // switching upon.
- 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 the default destination is unreachable, or if the lookup table covers
- // all values of the conditional variable, branch directly to the lookup table
- // BB. Otherwise, check that the condition is within the case range.
- const bool DefaultIsReachable =
- !isa<UnreachableInst>(SI->getDefaultDest()->getFirstNonPHIOrDbg());
- const bool GeneratingCoveredLookupTable = (MaxTableSize == TableSize);
BranchInst *RangeCheckBranch = nullptr;
if (!DefaultIsReachable || GeneratingCoveredLookupTable) {
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