From 522bd2337a1804c0a4a80e1d33f5982dfe512266 Mon Sep 17 00:00:00 2001
From: Leonard Grey <lgrey@chromium.org>
Date: Thu, 17 Nov 2022 11:37:26 -0500
Subject: [PATCH] Speed up testing for multiple functions at an address on
 Posix

The way this was originally written blows up on large enough targets
(like...Chromium :/). This change adds a set for amortized constant
time lookup of whether a FUNC already exists at a given address.

Bug: google-breakpad:751
Change-Id: I10a322da70f769c106e1e5f5b2dc3dc3f79444fd
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/4031580
Reviewed-by: Mark Mentovai <mark@chromium.org>
---
 src/common/module.cc | 30 +++++++++++++-----------------
 src/common/module.h  |  2 ++
 2 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/src/common/module.cc b/src/common/module.cc
index 4c427da1..442b910d 100644
--- a/src/common/module.cc
+++ b/src/common/module.cc
@@ -174,26 +174,22 @@ bool Module::AddFunction(Function* function) {
     }
   }
 #endif
-  if (enable_multiple_field_) {
+  if (enable_multiple_field_ && function_addresses_.count(function->address)) {
     FunctionSet::iterator existing_function = std::find_if(
         functions_.begin(), functions_.end(),
         [&](Function* other) { return other->address == function->address; });
-    if (existing_function != functions_.end()) {
-      (*existing_function)->is_multiple = true;
-      // Free the duplicate that was not inserted because this Module
-      // now owns it.
-      return false;
-    }
-    std::pair<FunctionSet::iterator, bool> ret = functions_.insert(function);
-    // We just checked!
-    assert(ret.second);
-  } else {
-    std::pair<FunctionSet::iterator, bool> ret = functions_.insert(function);
-    if (!ret.second && (*ret.first != function)) {
-      // Free the duplicate that was not inserted because this Module
-      // now owns it.
-      return false;
-    }
+    assert(existing_function != functions_.end());
+    (*existing_function)->is_multiple = true;
+    // Free the duplicate that was not inserted because this Module
+    // now owns it.
+    return false;
+  }
+  function_addresses_.emplace(function->address);
+  std::pair<FunctionSet::iterator, bool> ret = functions_.insert(function);
+  if (!ret.second && (*ret.first != function)) {
+    // Free the duplicate that was not inserted because this Module
+    // now owns it.
+    return false;
   }
   return true;
 }
diff --git a/src/common/module.h b/src/common/module.h
index f5031ea6..a8fcc81e 100644
--- a/src/common/module.h
+++ b/src/common/module.h
@@ -472,6 +472,8 @@ class Module {
   // point to.
   FileByNameMap files_;    // This module's source files.
   FunctionSet functions_;  // This module's functions.
+  // Used to quickly look up whether a function exists at a particular address.
+  unordered_set<Address> function_addresses_;
 
   // The module owns all the call frame info entries that have been
   // added to it.