llvm-dwp: Add an abstraction for the DWP string pool
Also reference strings in the memory mapped file, reduces memory usage
on a large test case by 18.5%.
llvm-svn: 270449
diff --git a/llvm/tools/llvm-dwp/DWPStringPool.h b/llvm/tools/llvm-dwp/DWPStringPool.h
new file mode 100644
index 0000000..8923e4c
--- /dev/null
+++ b/llvm/tools/llvm-dwp/DWPStringPool.h
@@ -0,0 +1,54 @@
+#ifndef TOOLS_LLVM_DWP_DWPSTRINGPOOL
+#define TOOLS_LLVM_DWP_DWPSTRINGPOOL
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/MC/MCSection.h"
+#include "llvm/MC/MCStreamer.h"
+#include <cassert>
+
+class DWPStringPool {
+
+ struct CStrDenseMapInfo {
+ static inline const char *getEmptyKey() {
+ return reinterpret_cast<const char *>(~static_cast<uintptr_t>(0));
+ }
+ static inline const char *getTombstoneKey() {
+ return reinterpret_cast<const char *>(~static_cast<uintptr_t>(1));
+ }
+ static unsigned getHashValue(const char *Val) {
+ assert(Val != getEmptyKey() && "Cannot hash the empty key!");
+ assert(Val != getTombstoneKey() && "Cannot hash the tombstone key!");
+ return (unsigned)hash_value(StringRef(Val));
+ }
+ static bool isEqual(const char *LHS, const char *RHS) {
+ if (RHS == getEmptyKey())
+ return LHS == getEmptyKey();
+ if (RHS == getTombstoneKey())
+ return LHS == getTombstoneKey();
+ return strcmp(LHS, RHS) == 0;
+ }
+ };
+
+ MCStreamer &Out;
+ MCSection *Sec;
+ DenseMap<const char *, uint32_t, CStrDenseMapInfo> Pool;
+ uint32_t Offset = 0;
+
+public:
+ DWPStringPool(MCStreamer &Out, MCSection *Sec) : Out(Out), Sec(Sec) {}
+
+ uint32_t getOffset(const char *Str, unsigned Length) {
+ assert(strlen(Str) + 1 == Length && "Ensure length hint is correct");
+
+ auto Pair = Pool.insert(std::make_pair(Str, Offset));
+ if (Pair.second) {
+ Out.SwitchSection(Sec);
+ Out.EmitBytes(StringRef(Str, Length));
+ Offset += Length;
+ }
+
+ return Pair.first->second;
+ }
+};
+
+#endif