From: David Majnemer <david.majnemer@gmail.com>
Date: Mon, 16 May 2016 20:30:03 +0000 (+0000)
Subject: [Lex] inferModuleFromLocation should do no work if there are no modules
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=bd4a20bc9c477ee19112ea4d9440d0823bfa38b1;p=clang

[Lex] inferModuleFromLocation should do no work if there are no modules

getModuleContainingLocation ends up on the hot-path for typical C code
which can lead to calls to getFileIDSlow.

To speed this up, short circuit inferModuleFromLocation when there
aren't any modules, implicit or otherwise.

This shaves 4-5% build time when building the linux kernel.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@269687 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Lex/ModuleMap.cpp b/lib/Lex/ModuleMap.cpp
index 51477185ae..3e3215dee8 100644
--- a/lib/Lex/ModuleMap.cpp
+++ b/lib/Lex/ModuleMap.cpp
@@ -917,6 +917,9 @@ Module *ModuleMap::inferModuleFromLocation(FullSourceLoc Loc) {
   if (Loc.isInvalid())
     return nullptr;
 
+  if (UmbrellaDirs.empty() && Headers.empty())
+    return nullptr;
+
   // Use the expansion location to determine which module we're in.
   FullSourceLoc ExpansionLoc = Loc.getExpansionLoc();
   if (!ExpansionLoc.isFileID())