Use TargetTransformInfo to control switch-to-lookup table transformation
When the switch-to-lookup tables transform landed in SimplifyCFG, it
was pointed out that this could be inappropriate for some targets.
Since there was no way at the time for the pass to know anything about
the target, an awkward reverse-transform was added in CodeGenPrepare
that turned lookup tables back into switches for some targets.
This patch uses the new TargetTransformInfo to determine if a
switch should be transformed, and removes
CodeGenPrepare::ConvertLoadToSwitch.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167011 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index f05a8ba..04ffc90 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -14,6 +14,7 @@
#define DEBUG_TYPE "simplifycfg"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Constants.h"
+#include "llvm/DataLayout.h"
#include "llvm/DerivedTypes.h"
#include "llvm/GlobalVariable.h"
#include "llvm/IRBuilder.h"
@@ -39,7 +40,7 @@
#include "llvm/Support/Debug.h"
#include "llvm/Support/NoFolder.h"
#include "llvm/Support/raw_ostream.h"
-#include "llvm/DataLayout.h"
+#include "llvm/TargetTransformInfo.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include <algorithm>
#include <set>
@@ -82,6 +83,7 @@
class SimplifyCFGOpt {
const DataLayout *const TD;
+ const TargetTransformInfo *const TTI;
Value *isValueEqualityComparison(TerminatorInst *TI);
BasicBlock *GetValueEqualityComparisonCases(TerminatorInst *TI,
@@ -101,7 +103,8 @@
bool SimplifyCondBranch(BranchInst *BI, IRBuilder <>&Builder);
public:
- explicit SimplifyCFGOpt(const DataLayout *td) : TD(td) {}
+ SimplifyCFGOpt(const DataLayout *td, const TargetTransformInfo *tti)
+ : TD(td), TTI(tti) {}
bool run(BasicBlock *BB);
};
}
@@ -3459,8 +3462,13 @@
/// replace the switch with lookup tables.
static bool SwitchToLookupTable(SwitchInst *SI,
IRBuilder<> &Builder,
- const DataLayout* TD) {
+ const DataLayout* TD,
+ const TargetTransformInfo *TTI) {
assert(SI->getNumCases() > 1 && "Degenerate switch?");
+
+ if (TTI && !TTI->getScalarTargetTransformInfo()->shouldBuildLookupTables())
+ return false;
+
// FIXME: Handle unreachable cases.
// FIXME: If the switch is too sparse for a lookup table, perhaps we could
@@ -3619,7 +3627,7 @@
if (ForwardSwitchConditionToPHI(SI))
return SimplifyCFG(BB) | true;
- if (SwitchToLookupTable(SI, Builder, TD))
+ if (SwitchToLookupTable(SI, Builder, TD, TTI))
return SimplifyCFG(BB) | true;
return false;
@@ -3916,6 +3924,7 @@
/// eliminates unreachable basic blocks, and does other "peephole" optimization
/// of the CFG. It returns true if a modification was made.
///
-bool llvm::SimplifyCFG(BasicBlock *BB, const DataLayout *TD) {
- return SimplifyCFGOpt(TD).run(BB);
+bool llvm::SimplifyCFG(BasicBlock *BB, const DataLayout *TD,
+ const TargetTransformInfo *TTI) {
+ return SimplifyCFGOpt(TD, TTI).run(BB);
}