[sancov] specifying comdat for sancov constructors

[aizatsky]

Updated ctor registration.

[aizatsky]

update

[aizatsky]

Related test and documentation update:

https://reviews.llvm.org/D29721
https://reviews.llvm.org/D29722

[kcc]

code ok, but please add a lit test, e.g. extend test/Instrumentation/SanitizerCoverage/coverage.ll or some other nearby

[aizatsky]

added .ll test

[aizatsky]

I've added the test. PTAL.

[kcc]

LGTM

[aizatsky]

Grhhh. Fails on mac :(

fatal error: error in backend: MachO doesn't support COMDATs, 'sancov.module_ctor' cannot be lowered.

I'll rollback and will see what I can do.

llvm/trunk/lib/Transforms/Instrumentation/SanitizerCoverage.cpp

if (HasSancovGuardsSection) {
       SecEnd->setVisibility(GlobalValue::HiddenVisibility);
 
       std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
           M, SanCovModuleCtorName, SanCovTracePCGuardInitName,
           {Int32PtrTy, Int32PtrTy},
           {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;
     std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
         M, SanCovModuleCtorName, SanCovModuleInitName,
         {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
         {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
          ConstantInt::get(IntptrTy, N),

llvm/trunk/test/Instrumentation/SanitizerCoverage/coverage.ll

 ; RUN: opt < %s -sancov -sanitizer-coverage-level=0 -S | FileCheck %s --check-prefix=CHECK0
 ; RUN: opt < %s -sancov -sanitizer-coverage-level=1 -S | FileCheck %s --check-prefix=CHECK1
 ; RUN: opt < %s -sancov -sanitizer-coverage-level=2 -S | FileCheck %s --check-prefix=CHECK_WITH_CHECK
 ; RUN: opt < %s -sancov -sanitizer-coverage-level=2 -sanitizer-coverage-block-threshold=10 -S | FileCheck %s --check-prefix=CHECK2
 ; RUN: opt < %s -sancov -sanitizer-coverage-level=2 -sanitizer-coverage-block-threshold=0  -S | FileCheck %s --check-prefix=CHECK_WITH_CHECK
 ; RUN: opt < %s -sancov -sanitizer-coverage-level=2 -sanitizer-coverage-block-threshold=1  -S | FileCheck %s --check-prefix=CHECK_WITH_CHECK
 ; 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 \
 ; RUN:      -S | FileCheck %s --check-prefix=CHECK2
 ; RUN: opt < %s -sancov -sanitizer-coverage-level=2 -sanitizer-coverage-block-threshold=1 \
 ; RUN:      -S | FileCheck %s --check-prefix=CHECK_WITH_CHECK
 ; RUN: opt < %s -sancov -sanitizer-coverage-level=3 -sanitizer-coverage-prune-blocks=1 -S | FileCheck %s --check-prefix=CHECKPRUNE
 

 ; CHECK_TRACE_PC: call void asm sideeffect "", ""()
 ; CHECK_TRACE_PC: ret void
 
 ; CHECK_TRACE_PC-LABEL: define void @CallViaVptr
 ; CHECK_TRACE_PC: call void @__sanitizer_cov_trace_pc_indir
 ; 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
 }
 
 ; CHECK4-LABEL: define void @call_unreachable
 ; CHECK4-NOT: __sanitizer_cov
 ; CHECK4: unreachable
 
 ; CHECKPRUNE-LABEL: define void @foo
 ; CHECKPRUNE: call void @__sanitizer_cov
 ; CHECKPRUNE: call void @__sanitizer_cov
 ; CHECKPRUNE: call void @__sanitizer_cov
 ; CHECKPRUNE-NOT: call void @__sanitizer_cov
 ; CHECKPRUNE: ret void