[PATCH] D48203: [SanitizerCoverage] Add associated metadata to pc-tables.

[Matt Morehouse via Phabricator via llvm-commits]

morehouse created this revision.
morehouse added a reviewer: eugenis.
Herald added a subscriber: hiraditya.

Using associated metadata rather than llvm.used allows linkers to
perform dead stripping with -fsanitize-coverage=pc-table.  Unfortunately
in my local tests, LLD was the only linker that made use of this metadata.


https://reviews.llvm.org/D48203

Files:
  compiler-rt/test/fuzzer/gc-sections.test
  llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp


Index: llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
+++ llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
@@ -598,7 +598,8 @@
   }
   if (Options.PCTable) {
     FunctionPCsArray = CreatePCArray(F, AllBlocks);
-    GlobalsToAppendToUsed.push_back(FunctionPCsArray);
+    MDNode *MD = MDNode::get(F.getContext(), ValueAsMetadata::get(&F));
+    FunctionPCsArray->addMetadata(LLVMContext::MD_associated, *MD);
   }
 }
 
Index: compiler-rt/test/fuzzer/gc-sections.test
===================================================================
--- compiler-rt/test/fuzzer/gc-sections.test
+++ compiler-rt/test/fuzzer/gc-sections.test
@@ -5,8 +5,8 @@
 RUN: nm %t | grep UnusedFunctionShouldBeRemovedByLinker | count 1
 
 With gc-sections. Currently, we can't remove unused code.
-DISABLED: %cpp_compiler %S/GcSectionsTest.cpp -o %t -ffunction-sections -Wl,-gc-sections
-DISABLED: nm %t | grep UnusedFunctionShouldBeRemovedByLinker | count 1
+RUN: %cpp_compiler %S/GcSectionsTest.cpp -o %t -ffunction-sections -Wl,-gc-sections -fuse-ld=lld
+RUN: nm %t | not grep UnusedFunctionShouldBeRemovedByLinker
 
 With gc sections, with trace-pc. Unused code is removed.
 RUN: %cpp_compiler %S/GcSectionsTest.cpp -o %t -fsanitize-coverage=0 -fsanitize-coverage=trace-pc -ffunction-sections -Wl,-gc-sections


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D48203.151447.patch
Type: text/x-patch
Size: 1436 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20180615/5ab32303/attachment.bin>