[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

1 files changed, 5 insertions, 4 deletions

diff --git a/llvm/tools/llvm-objdump/llvm-objdump.cpp b/llvm/tools/llvm-objdump/llvm-objdump.cpp
index bf8487b..4e78e26 100644
--- a/llvm/tools/llvm-objdump/llvm-objdump.cpp
+++ b/llvm/tools/llvm-objdump/llvm-objdump.cpp
@@ -97,18 +97,19 @@ using namespace llvm::opt;
 
 namespace {
 
-class CommonOptTable : public opt::OptTable {
+class CommonOptTable : public opt::GenericOptTable {
 public:
   CommonOptTable(ArrayRef<Info> OptionInfos, const char *Usage,
                  const char *Description)
-      : OptTable(OptionInfos), Usage(Usage), Description(Description) {
+      : opt::GenericOptTable(OptionInfos), Usage(Usage),
+        Description(Description) {
     setGroupedShortOptions(true);
   }
 
   void printHelp(StringRef Argv0, bool ShowHidden = false) const {
     Argv0 = sys::path::filename(Argv0);
-    opt::OptTable::printHelp(outs(), (Argv0 + Usage).str().c_str(), Description,
-                             ShowHidden, ShowHidden);
+    opt::GenericOptTable::printHelp(outs(), (Argv0 + Usage).str().c_str(),
+                                    Description, ShowHidden, ShowHidden);
     // TODO Replace this with OptTable API once it adds extrahelp support.
     outs() << "\nPass @FILE as argument to read options from FILE.\n";
   }