Re-land "[MergeICmps] Disable mergeicmps if the target does not want to handle memcmp expansion."
(fixed unit tests by making comparisons stable)
This reverts commit 1b2d359ce256fd6737da4e93833346a0bd6d7583.
llvm-svn: 315056
diff --git a/llvm/lib/Transforms/Scalar/MergeICmps.cpp b/llvm/lib/Transforms/Scalar/MergeICmps.cpp
index a56cffc..1244a97 100644
--- a/llvm/lib/Transforms/Scalar/MergeICmps.cpp
+++ b/llvm/lib/Transforms/Scalar/MergeICmps.cpp
@@ -28,6 +28,8 @@
#include <vector>
#include "llvm/ADT/APSInt.h"
#include "llvm/Analysis/Loads.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/IntrinsicInst.h"
@@ -41,8 +43,6 @@
#define DEBUG_TYPE "mergeicmps"
-#define MERGEICMPS_DOT_ON
-
// A BCE atom.
struct BCEAtom {
BCEAtom() : GEP(nullptr), LoadI(nullptr), Offset() {}
@@ -50,7 +50,21 @@
const Value *Base() const { return GEP ? GEP->getPointerOperand() : nullptr; }
bool operator<(const BCEAtom &O) const {
- return Base() == O.Base() ? Offset.slt(O.Offset) : Base() < O.Base();
+ assert(Base() && "invalid atom");
+ assert(O.Base() && "invalid atom");
+ // Just ordering by (Base(), Offset) is sufficient. However because this
+ // means that the ordering will depend on the addresses of the base
+ // values, which are not reproducible from run to run. To guarantee
+ // stability, we use the names of the values if they exist; we sort by:
+ // (Base.getName(), Base(), Offset).
+ const int NameCmp = Base()->getName().compare(O.Base()->getName());
+ if (NameCmp == 0) {
+ if (Base() == O.Base()) {
+ return Offset.slt(O.Offset);
+ }
+ return Base() < O.Base();
+ }
+ return NameCmp < 0;
}
GetElementPtrInst *GEP;
@@ -99,7 +113,9 @@
// A basic block with a comparison between two BCE atoms.
// Note: the terminology is misleading: the comparison is symmetric, so there
-// is no real {l/r}hs. To break the symmetry, we use the smallest atom as Lhs.
+// is no real {l/r}hs. What we want though is to have the same base on the
+// left (resp. right), so that we can detect consecutive loads. To ensure this
+// we put the smallest atom on the left.
class BCECmpBlock {
public:
BCECmpBlock() {}
@@ -430,10 +446,9 @@
IRBuilder<> Builder(BB);
const auto &DL = Phi.getModule()->getDataLayout();
- Value *const MemCmpCall =
- emitMemCmp(FirstComparison.Lhs().GEP, FirstComparison.Rhs().GEP,
- ConstantInt::get(DL.getIntPtrType(Context), TotalSize),
- Builder, DL, TLI);
+ Value *const MemCmpCall = emitMemCmp(
+ FirstComparison.Lhs().GEP, FirstComparison.Rhs().GEP, ConstantInt::get(DL.getIntPtrType(Context), TotalSize),
+ Builder, DL, TLI);
Value *const MemCmpIsZero = Builder.CreateICmpEQ(
MemCmpCall, ConstantInt::get(Type::getInt32Ty(Context), 0));
@@ -589,22 +604,30 @@
bool runOnFunction(Function &F) override {
if (skipFunction(F)) return false;
const auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
- auto PA = runImpl(F, &TLI);
+ const auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
+ auto PA = runImpl(F, &TLI, &TTI);
return !PA.areAllPreserved();
}
private:
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<TargetLibraryInfoWrapperPass>();
+ AU.addRequired<TargetTransformInfoWrapperPass>();
}
- PreservedAnalyses runImpl(Function &F, const TargetLibraryInfo *TLI);
+ PreservedAnalyses runImpl(Function &F, const TargetLibraryInfo *TLI,
+ const TargetTransformInfo *TTI);
};
-PreservedAnalyses MergeICmps::runImpl(Function &F,
- const TargetLibraryInfo *TLI) {
+PreservedAnalyses MergeICmps::runImpl(Function &F, const TargetLibraryInfo *TLI,
+ const TargetTransformInfo *TTI) {
DEBUG(dbgs() << "MergeICmpsPass: " << F.getName() << "\n");
+ // We only try merging comparisons if the target wants to expand memcmp later.
+ // The rationale is to avoid turning small chains into memcmp calls.
+ unsigned MaxLoadSize;
+ if (!TTI->enableMemCmpExpansion(MaxLoadSize)) return PreservedAnalyses::all();
+
bool MadeChange = false;
for (auto BBIt = ++F.begin(); BBIt != F.end(); ++BBIt) {
@@ -623,6 +646,7 @@
INITIALIZE_PASS_BEGIN(MergeICmps, "mergeicmps",
"Merge contiguous icmps into a memcmp", false, false)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
INITIALIZE_PASS_END(MergeICmps, "mergeicmps",
"Merge contiguous icmps into a memcmp", false, false)