Handle more edge cases in intrinsic name binary search

I tried to make the AMDGPU intrinsic info table use this instead of
another StringMatcher, and some issues arose.

llvm-svn: 258871

1 files changed, 39 insertions, 0 deletions

diff --git a/llvm/lib/IR/IntrinsicInst.cpp b/llvm/lib/IR/IntrinsicInst.cpp
index b9b5a29091d..427cfef5fa3 100644
--- a/llvm/lib/IR/IntrinsicInst.cpp
+++ b/llvm/lib/IR/IntrinsicInst.cpp
@@ -25,6 +25,7 @@
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/Metadata.h"
+#include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 
 //===----------------------------------------------------------------------===//
@@ -79,3 +80,41 @@ const Value *DbgValueInst::getValue() const {
 }
 
 Value *DbgValueInst::getValue() { return getValueImpl(getArgOperand(0)); }
+
+int llvm::Intrinsic::lookupLLVMIntrinsicByName(ArrayRef<const char *> NameTable,
+                                               StringRef Name) {
+  assert(Name.startswith("llvm."));
+
+  // Do successive binary searches of the dotted name components. For
+  // "llvm.gc.experimental.statepoint.p1i8.p1i32", we will find the range of
+  // intrinsics starting with "llvm.gc", then "llvm.gc.experimental", then
+  // "llvm.gc.experimental.statepoint", and then we will stop as the range is
+  // size 1. During the search, we can skip the prefix that we already know is
+  // identical. By using strncmp we consider names with differing suffixes to
+  // be part of the equal range.
+  size_t CmpStart = 0;
+  size_t CmpEnd = 4; // Skip the "llvm" component.
+  const char *const *Low = NameTable.begin();
+  const char *const *High = NameTable.end();
+  const char *const *LastLow = Low;
+  while (CmpEnd < Name.size() && High - Low > 0) {
+    CmpStart = CmpEnd;
+    CmpEnd = Name.find('.', CmpStart + 1);
+    CmpEnd = CmpEnd == StringRef::npos ? Name.size() : CmpEnd;
+    auto Cmp = [CmpStart, CmpEnd](const char *LHS, const char *RHS) {
+      return strncmp(LHS + CmpStart, RHS + CmpStart, CmpEnd - CmpStart) < 0;
+    };
+    LastLow = Low;
+    std::tie(Low, High) = std::equal_range(Low, High, Name.data(), Cmp);
+  }
+  if (High - Low > 0)
+    LastLow = Low;
+
+  if (LastLow == NameTable.end())
+    return -1;
+  StringRef NameFound = *LastLow;
+  if (Name == NameFound ||
+      (Name.startswith(NameFound) && Name[NameFound.size()] == '.'))
+    return LastLow - NameTable.begin();
+  return -1;
+}