[llvm] [AggressiveInstCombine] Expand strchr/memchr with small constant strings (PR #98501)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Sat Jul 13 10:00:07 PDT 2024
================
@@ -1103,6 +1108,85 @@ void StrNCmpInliner::inlineCompare(Value *LHS, StringRef RHS, uint64_t N,
}
}
+/// Convert strchr/memchr with a small constant string into a switch
+static bool foldStrChr(CallInst *Call, LibFunc Func, DomTreeUpdater *DTU,
+ const DataLayout &DL) {
+ assert((Func == LibFunc_strchr || Func == LibFunc_memchr) &&
+ "Unexpected LibFunc");
+ if (isa<Constant>(Call->getArgOperand(1)))
+ return false;
+
+ StringRef Str;
+ Value *Base = Call->getArgOperand(0);
+ if (!getConstantStringInfo(Base, Str, /*TrimAtNul=*/Func == LibFunc_strchr))
+ return false;
+
+ uint64_t N = Str.size();
+ if (Func == LibFunc_memchr) {
+ if (auto *ConstInt = dyn_cast<ConstantInt>(Call->getArgOperand(2))) {
+ uint64_t Val = ConstInt->getZExtValue();
+ /// Ignore the case that n is larger than the size of string.
----------------
nikic wrote:
```suggestion
// Ignore the case that n is larger than the size of string.
```
https://github.com/llvm/llvm-project/pull/98501
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