[sancov] using comdat only when it is enabled

[kcc]

LGTM
bogner@ FYI

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)});
 
+      if (TargetTriple.supportsCOMDAT()) {
         // Use comdat to dedup CtorFunc.
         CtorFunc->setComdat(M.getOrInsertComdat(SanCovModuleCtorName));
         appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority, CtorFunc);
+      } else {
+        appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
+      }
     }
   } 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),

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_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

test/Instrumentation/SanitizerCoverage/trace-pc-guard-comdat.ll

+; RUN: opt < %s -sancov -sanitizer-coverage-level=4 -sanitizer-coverage-trace-pc-guard  -S | FileCheck %s --check-prefix=CHECK_TRACE_PC_GUARD
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-unknown-linux-gnu"
+define void @foo(i32* %a) sanitize_address {
+entry:
+  %tobool = icmp eq i32* %a, null
+  br i1 %tobool, label %if.end, label %if.then
+
+  if.then:                                          ; preds = %entry
+  store i32 0, i32* %a, align 4
+  br label %if.end
+
+  if.end:                                           ; preds = %entry, %if.then
+  ret void
+}
+
+%struct.StructWithVptr = type { i32 (...)** }
+
+define void @CallViaVptr(%struct.StructWithVptr* %foo) uwtable sanitize_address {
+entry:
+  %0 = bitcast %struct.StructWithVptr* %foo to void (%struct.StructWithVptr*)***
+  %vtable = load void (%struct.StructWithVptr*)**, void (%struct.StructWithVptr*)*** %0, align 8
+  %1 = load void (%struct.StructWithVptr*)*, void (%struct.StructWithVptr*)** %vtable, align 8
+  tail call void %1(%struct.StructWithVptr* %foo)
+  tail call void %1(%struct.StructWithVptr* %foo)
+  tail call void asm sideeffect "", ""()
+  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
+

test/Instrumentation/SanitizerCoverage/trace-pc-guard-nocomdat.ll

+; RUN: opt < %s -sancov -sanitizer-coverage-level=4 -sanitizer-coverage-trace-pc-guard  -S | FileCheck %s --check-prefix=CHECK_TRACE_PC_GUARD
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-apple-darwin10.0.0"
+define void @foo(i32* %a) sanitize_address {
+entry:
+  %tobool = icmp eq i32* %a, null
+  br i1 %tobool, label %if.end, label %if.then
+
+  if.then:                                          ; preds = %entry
+  store i32 0, i32* %a, align 4
+  br label %if.end
+
+  if.end:                                           ; preds = %entry, %if.then
+  ret void
+}
+
+%struct.StructWithVptr = type { i32 (...)** }
+
+define void @CallViaVptr(%struct.StructWithVptr* %foo) uwtable sanitize_address {
+entry:
+  %0 = bitcast %struct.StructWithVptr* %foo to void (%struct.StructWithVptr*)***
+  %vtable = load void (%struct.StructWithVptr*)**, void (%struct.StructWithVptr*)*** %0, align 8
+  %1 = load void (%struct.StructWithVptr*)*, void (%struct.StructWithVptr*)** %vtable, align 8
+  tail call void %1(%struct.StructWithVptr* %foo)
+  tail call void %1(%struct.StructWithVptr* %foo)
+  tail call void asm sideeffect "", ""()
+  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() {
+