[OptTable] Precompute OptTable prefixes union table through tablegen

This avoid rediscovering this table when reading each options, providing
a sensible 2% speedup when processing and empty file, and a measurable
speedup on typical workloads, see:

This is optional, the legacy, on-the-fly, approach can still be used
through the GenericOptTable class, while the new one is used through
PrecomputedOptTable.

https://llvm-compile-time-tracker.com/compare.php?from=4da6cb3202817ee2897d6b690e4af950459caea4&to=19a492b704e8f5c1dea120b9c0d3859bd78796be&stat=instructions:u

Differential Revision: https://reviews.llvm.org/D140800

2 files changed, 4 insertions, 5 deletions

diff --git a/llvm/lib/ToolDrivers/llvm-dlltool/DlltoolDriver.cpp b/llvm/lib/ToolDrivers/llvm-dlltool/DlltoolDriver.cpp
index 375c455..7d8bf2b 100644
--- a/llvm/lib/ToolDrivers/llvm-dlltool/DlltoolDriver.cpp
+++ b/llvm/lib/ToolDrivers/llvm-dlltool/DlltoolDriver.cpp
@@ -52,9 +52,9 @@ static constexpr opt::OptTable::Info InfoTable[] = {
 #undef OPTION
 };
 
-class DllOptTable : public llvm::opt::OptTable {
+class DllOptTable : public opt::GenericOptTable {
 public:
-  DllOptTable() : OptTable(InfoTable, false) {}
+  DllOptTable() : opt::GenericOptTable(InfoTable, false) {}
 };
 
 // Opens a file. Path has to be resolved already.
diff --git a/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp b/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp
index b0046e0..ade753a 100644
--- a/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp
+++ b/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp
@@ -56,11 +56,10 @@ static constexpr opt::OptTable::Info InfoTable[] = {
 #undef OPTION
 };
 
-class LibOptTable : public opt::OptTable {
+class LibOptTable : public opt::GenericOptTable {
 public:
-  LibOptTable() : OptTable(InfoTable, true) {}
+  LibOptTable() : opt::GenericOptTable(InfoTable, true) {}
 };
-
 }
 
 static std::string getDefaultOutputPath(const NewArchiveMember &FirstMember) {