[PATCH] D85538: [Clang options] Optimize optionMatches() runtime by removing mallocs

[Nadav Rotem via Phabricator via llvm-commits]

nadav created this revision.
nadav added a reviewer: modocache.
Herald added subscribers: llvm-commits, hiraditya.
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The method optionMatches() constructs 9865 std::string instances when comparing different
options. Many of these instances exceed the size of the internal storage and force memory
allocations. This patch adds an early exit check that eliminates almost most of the string allocations
while keeping the code simple.

Example inputs: 
Prefix: /, Name: Fr
Prefix: -, Name: Fr
Prefix: -, Name: fsanitize-address-field-padding=
Prefix: -, Name: fsanitize-address-globals-dead-stripping
Prefix: -, Name: fsanitize-address-poison-custom-array-cookie
Prefix: -, Name: fsanitize-address-use-after-scope
Prefix: -, Name: fsanitize-address-use-odr-indicator
Prefix: -, Name: fsanitize-blacklist=


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D85538

Files:
  llvm/lib/Option/OptTable.cpp


Index: llvm/lib/Option/OptTable.cpp
===================================================================
--- llvm/lib/Option/OptTable.cpp
+++ llvm/lib/Option/OptTable.cpp
@@ -198,8 +198,9 @@
 static bool optionMatches(const OptTable::Info &In, StringRef Option) {
   if (In.Prefixes)
     for (size_t I = 0; In.Prefixes[I]; I++)
-      if (Option == std::string(In.Prefixes[I]) + In.Name)
-        return true;
+      if (Option.endswith(In.Name))
+        if (Option == std::string(In.Prefixes[I]) + In.Name)
+          return true;
   return false;
 }
 


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