[sancov] specifying comdat for sancov constructors

Differential Revision: https://reviews.llvm.org/D29662

llvm-svn: 294517

llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp

@@ -382,7 +382,9 @@ bool SanitizerCoverageModule::runOnModule(Module &M) {
           {IRB.CreatePointerCast(SecStart, Int32PtrTy),
             IRB.CreatePointerCast(SecEnd, Int32PtrTy)});
 
-      appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
+      // Use comdat to dedup CtorFunc.
+      CtorFunc->setComdat(M.getOrInsertComdat(SanCovModuleCtorName));
+      appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority, CtorFunc);
     }
   } else if (!Options.TracePC) {
     Function *CtorFunc;

llvm/test/Instrumentation/SanitizerCoverage/coverage.ll

@@ -7,7 +7,7 @@
 ; RUN: opt < %s -sancov -sanitizer-coverage-level=3 -sanitizer-coverage-block-threshold=10 -S | FileCheck %s --check-prefix=CHECK3
 ; RUN: opt < %s -sancov -sanitizer-coverage-level=4 -S | FileCheck %s --check-prefix=CHECK4
 ; RUN: opt < %s -sancov -sanitizer-coverage-level=4 -sanitizer-coverage-trace-pc  -S | FileCheck %s --check-prefix=CHECK_TRACE_PC
-; RUN: opt < %s -sancov -sanitizer-coverage-level=4 -sanitizer-coverage-trace-pc-guard  -S | FileCheck %s --check-prefix=CHECK_TRACE_PC
+; RUN: opt < %s -sancov -sanitizer-coverage-level=4 -sanitizer-coverage-trace-pc-guard  -S | FileCheck %s --check-prefix=CHECK_TRACE_PC_GUARD
 ; RUN: opt < %s -sancov -sanitizer-coverage-level=3 -sanitizer-coverage-8bit-counters=1  -S | FileCheck %s --check-prefix=CHECK-8BIT
 
 ; RUN: opt < %s -sancov -sanitizer-coverage-level=2 -sanitizer-coverage-block-threshold=10 \
@@ -131,6 +131,18 @@ entry:
 ; CHECK_TRACE_PC: call void @__sanitizer_cov_trace_pc_indir
 ; CHECK_TRACE_PC: ret void
 
+; CHECK_TRACE_PC_GUARD-LABEL: define void @foo
+; CHECK_TRACE_PC_GUARD: call void @__sanitizer_cov_trace_pc
+; CHECK_TRACE_PC_GUARD: call void asm sideeffect "", ""()
+; CHECK_TRACE_PC_GUARD: ret void
+
+; CHECK_TRACE_PC_GUARD-LABEL: define void @CallViaVptr
+; CHECK_TRACE_PC_GUARD: call void @__sanitizer_cov_trace_pc_indir
+; CHECK_TRACE_PC_GUARD: call void @__sanitizer_cov_trace_pc_indir
+; CHECK_TRACE_PC_GUARD: ret void
+
+; CHECK_TRACE_PC_GUARD-LABEL: define internal void @sancov.module_ctor() comdat
+
 define void @call_unreachable() uwtable sanitize_address {
 entry:
   unreachable