GCOV: Make sure that function idents in the .gcda and .gcno match

When generating gcov compatible profiling, we sometimes skip emitting
data for functions for one reason or another. However, this was
emitting different function IDs in the .gcno and .gcda files, because
the .gcno case was using the loop index before skipping functions and
the .gcda the array index after. This resulted in completely invalid
gcov data.

This fixes the problem by making the .gcno loop track the ID
separately from the loop index.

llvm-svn: 221441

llvm/lib/IR/GCOV.cpp

@@ -298,7 +298,8 @@ uint64_t GCOVFunction::getExitCount() const {
 
 /// dump - Dump GCOVFunction content to dbgs() for debugging purposes.
 void GCOVFunction::dump() const {
-  dbgs() <<  "===== " << Name << " @ " << Filename << ":" << LineNumber << "\n";
+  dbgs() << "===== " << Name << " (" << Ident << ") @ " << Filename << ":"
+         << LineNumber << "\n";
   for (const auto &Block : Blocks)
     Block->dump();
 }

llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp

@@ -485,6 +485,7 @@ void GCOVProfiler::emitProfileNotes() {
     std::string EdgeDestinations;
 
     DIArray SPs = CU.getSubprograms();
+    unsigned FunctionIdent = 0;
     for (unsigned i = 0, e = SPs.getNumElements(); i != e; ++i) {
       DISubprogram SP(SPs.getElement(i));
       assert((!SP || SP.isSubprogram()) &&
@@ -504,8 +505,8 @@ void GCOVProfiler::emitProfileNotes() {
         ++It;
       EntryBlock.splitBasicBlock(It);
 
-      Funcs.push_back(
+      Funcs.push_back(make_unique<GCOVFunction>(SP, &out, FunctionIdent++,
-          make_unique<GCOVFunction>(SP, &out, i, Options.UseCfgChecksum));
+                                                Options.UseCfgChecksum));
       GCOVFunction &Func = *Funcs.back();
 
       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {

llvm/test/Transforms/GCOVProfiling/function-numbering.ll

@@ -0,0 +1,56 @@
+; Test that GCOV instrumentation numbers functions correctly when some
+; functions aren't emitted.
+
+; Inject metadata to set the .gcno file location
+; RUN: echo '!14 = metadata !{metadata !"%/T/function-numbering.ll", metadata !0}' > %t1
+; RUN: cat %s %t1 > %t2
+
+; RUN: opt -insert-gcov-profiling -S < %t2 | FileCheck --check-prefix GCDA %s
+; RUN: llvm-cov -n -dump %T/function-numbering.gcno 2>&1 | FileCheck --check-prefix GCNO %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.10.0"
+
+; GCDA: @[[FOO:[0-9]+]] = private unnamed_addr constant [4 x i8] c"foo\00"
+; GCDA-NOT: @{{[0-9]+}} = private unnamed_addr constant .* c"bar\00"
+; GCDA: @[[BAZ:[0-9]+]] = private unnamed_addr constant [4 x i8] c"baz\00"
+; GCDA: define internal void @__llvm_gcov_writeout()
+; GCDA: call void @llvm_gcda_emit_function(i32 0, i8* getelementptr inbounds ([4 x i8]* @[[FOO]]
+; GCDA: call void @llvm_gcda_emit_function(i32 1, i8* getelementptr inbounds ([4 x i8]* @[[BAZ]]
+
+; GCNO: == foo (0) @
+; GCNO-NOT: == bar ({{[0-9]+}}) @
+; GCNO: == baz (1) @
+
+define void @foo() {
+  ret void, !dbg !12
+}
+
+define void @bar() {
+  ; This function is referenced by the debug info, but no lines have locations.
+  ret void
+}
+
+define void @baz() {
+  ret void, !dbg !13
+}
+
+!llvm.gcov = !{!14}
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!9, !10}
+!llvm.ident = !{!11}
+
+!0 = metadata !{metadata !"0x11\0012\00clang version 3.6.0 \000\00\000\00\002", metadata !1, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2} ; [ DW_TAG_compile_unit ] [function-numbering.ll] [DW_LANG_C99]
+!1 = metadata !{metadata !".../llvm/test/Transforms/GCOVProfiling/function-numbering.ll", metadata !""}
+!2 = metadata !{}
+!3 = metadata !{metadata !4, metadata !7, metadata !8}
+!4 = metadata !{metadata !"0x2e\00foo\00foo\00\001\000\001\000\000\000\000\001", metadata !1, metadata !5, metadata !6, null, void ()* @foo, null, null, metadata !2} ; [ DW_TAG_subprogram ] [line 1] [def] [foo]
+!5 = metadata !{metadata !"0x29", metadata !1}    ; [ DW_TAG_file_type ] [/Users/bogner/build/llvm-debug//tmp/foo.c]
+!6 = metadata !{metadata !"0x15\00\000\000\000\000\000\000", null, null, null, metadata !2, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = metadata !{metadata !"0x2e\00bar\00bar\00\002\000\001\000\000\000\000\002", metadata !1, metadata !5, metadata !6, null, void ()* @bar, null, null, metadata !2} ; [ DW_TAG_subprogram ] [line 2] [def] [bar]
+!8 = metadata !{metadata !"0x2e\00baz\00baz\00\003\000\001\000\000\000\000\003", metadata !1, metadata !5, metadata !6, null, void ()* @baz, null, null, metadata !2} ; [ DW_TAG_subprogram ] [line 3] [def] [baz]
+!9 = metadata !{i32 2, metadata !"Dwarf Version", i32 2}
+!10 = metadata !{i32 2, metadata !"Debug Info Version", i32 2}
+!11 = metadata !{metadata !"clang version 3.6.0 "}
+!12 = metadata !{i32 1, i32 13, metadata !4, null}
+!13 = metadata !{i32 3, i32 13, metadata !8, null}