From efd319a2ad262e1ad3b4aa9c2f19ad36246ac0d5 Mon Sep 17 00:00:00 2001
From: Vedant Kumar <vsk@apple.com>
Date: Tue, 26 Jul 2016 00:24:59 +0000
Subject: [PATCH] [Coverage] Do not write out coverage mappings with zero
 entries

After r275121, we stopped mapping regions from system headers. Lambdas
declared in regions belonging to system headers started producing empty
coverage mappings, since the files corresponding to their spelling locs
were being ignored.

The coverage reader doesn't know what to do with these empty mappings.
This commit makes sure that we don't produce them and adds a test. I'll
make the reader stricter in a follow-up commit.

llvm-svn: 276716
---
 clang/lib/CodeGen/CoverageMappingGen.cpp              | 11 +++++++++++
 .../{system_macro.c => system_macro.cpp}              |  9 ++++++---
 2 files changed, 17 insertions(+), 3 deletions(-)
 rename clang/test/CoverageMapping/{system_macro.c => system_macro.cpp} (50%)

diff --git a/clang/lib/CodeGen/CoverageMappingGen.cpp b/clang/lib/CodeGen/CoverageMappingGen.cpp
index 4debc7e95065..da6fa2a37a3a 100644
--- a/clang/lib/CodeGen/CoverageMappingGen.cpp
+++ b/clang/lib/CodeGen/CoverageMappingGen.cpp
@@ -352,6 +352,9 @@ struct EmptyCoverageMappingBuilder : public CoverageMappingBuilder {
     gatherFileIDs(FileIDMapping);
     emitSourceRegions();
 
+    if (MappingRegions.empty())
+      return;
+
     CoverageMappingWriter Writer(FileIDMapping, None, MappingRegions);
     Writer.write(OS);
   }
@@ -605,6 +608,9 @@ struct CounterCoverageMappingBuilder
     emitExpansionRegions();
     gatherSkippedRegions();
 
+    if (MappingRegions.empty())
+      return;
+
     CoverageMappingWriter Writer(VirtualFileMapping, Builder.getExpressions(),
                                  MappingRegions);
     Writer.write(OS);
@@ -621,6 +627,11 @@ struct CounterCoverageMappingBuilder
 
   void VisitDecl(const Decl *D) {
     Stmt *Body = D->getBody();
+
+    // Do not propagate region counts into system headers.
+    if (Body && SM.isInSystemHeader(SM.getSpellingLoc(getStart(Body))))
+      return;
+
     propagateCounts(getRegionCounter(Body), Body);
   }
 
diff --git a/clang/test/CoverageMapping/system_macro.c b/clang/test/CoverageMapping/system_macro.cpp
similarity index 50%
rename from clang/test/CoverageMapping/system_macro.c
rename to clang/test/CoverageMapping/system_macro.cpp
index bddc822b0d90..ce0da17ce06c 100644
--- a/clang/test/CoverageMapping/system_macro.c
+++ b/clang/test/CoverageMapping/system_macro.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fprofile-instrument=clang -fcoverage-mapping -dump-coverage-mapping -emit-llvm-only -main-file-name system_macro.c -o - %s | FileCheck %s
+// RUN: %clang_cc1 -std=c++11 -fprofile-instrument=clang -fcoverage-mapping -dump-coverage-mapping -emit-llvm-only -main-file-name system_macro.cpp -o - %s | FileCheck %s
 
 #ifdef IS_SYSHEADER
 
@@ -11,13 +11,16 @@
 #define IS_SYSHEADER
 #include __FILE__
 
-// CHECK-LABEL: doSomething:
+// CHECK-LABEL: doSomething
 void doSomething(int x) { // CHECK: File 0, [[@LINE]]:25 -> {{[0-9:]+}} = #0
   Func(x);
   return;
   SomeType *f; // CHECK: File 0, [[@LINE]]:11 -> {{[0-9:]+}} = 0
 }
 
-int main() {}
+// CHECK-LABEL: main
+int main() { // CHECK: File 0, [[@LINE]]:12 -> [[@LINE+2]]:2 = #0
+  Func([] { return true; }());
+}
 
 #endif