[PGO] Simplify coverage mapping lowering

Coverage mapping data may reference names of functions
that are skipped by FE (e.g, unused inline functions). Since
those functions are skipped, normal instr-prof function lowering
pass won't put those names in the right section, so special 
handling is needed to walk through coverage mapping structure
and recollect the references.

With this patch, only names that are skipped are processed. This
simplifies the lowering code and it no longer needs to make 
assumptions coverage mapping data layout. It should also be 
more efficient.

llvm-svn: 257091

1 files changed, 11 insertions, 23 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp b/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
index 51ff95d9a74..28483e7e9b6 100644
--- a/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
+++ b/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
@@ -93,8 +93,8 @@ private:
   /// Replace instrprof_increment with an increment of the appropriate value.
   void lowerIncrement(InstrProfIncrementInst *Inc);
 
-  /// Set up the section and uses for coverage data and its references.
-  void lowerCoverageData(GlobalVariable *CoverageData);
+  /// Force emitting of name vars for unused functions.
+  void lowerCoverageData(GlobalVariable *CoverageNamesVar);
 
   /// Get the region counters for an increment, creating them if necessary.
   ///
@@ -156,9 +156,9 @@ bool InstrProfiling::runOnModule(Module &M) {
         }
       }
 
-  if (GlobalVariable *Coverage =
-          M.getNamedGlobal(getCoverageMappingVarName())) {
-    lowerCoverageData(Coverage);
+  if (GlobalVariable *CoverageNamesVar =
+          M.getNamedGlobal(getCoverageNamesVarName())) {
+    lowerCoverageData(CoverageNamesVar);
     MadeChange = true;
   }
 
@@ -233,28 +233,16 @@ void InstrProfiling::lowerIncrement(InstrProfIncrementInst *Inc) {
   Inc->eraseFromParent();
 }
 
-void InstrProfiling::lowerCoverageData(GlobalVariable *CoverageData) {
-
-  Constant *Init = CoverageData->getInitializer();
-  // We're expecting { [4 x 32], [n x { i8*, i32, i32 }], [m x i8] }
-  // for some C. If not, the frontend's given us something broken.
-  assert(Init->getNumOperands() == 3 && "bad number of fields in coverage map");
-  assert(isa<ConstantArray>(Init->getAggregateElement(1)) &&
-         "invalid function list in coverage map");
-  ConstantArray *Records = cast<ConstantArray>(Init->getAggregateElement(1));
-  for (unsigned I = 0, E = Records->getNumOperands(); I < E; ++I) {
-    Constant *Record = Records->getOperand(I);
-    Value *V = const_cast<Value *>(Record->getOperand(0))->stripPointerCasts();
+void InstrProfiling::lowerCoverageData(GlobalVariable *CoverageNamesVar) {
 
+  ConstantArray *Names =
+      cast<ConstantArray>(CoverageNamesVar->getInitializer());
+  for (unsigned I = 0, E = Names->getNumOperands(); I < E; ++I) {
+    Constant *NC = Names->getOperand(I);
+    Value *V = NC->stripPointerCasts();
     assert(isa<GlobalVariable>(V) && "Missing reference to function name");
     GlobalVariable *Name = cast<GlobalVariable>(V);
 
-    // If we have region counters for this name, we've already handled it.
-    auto It = ProfileDataMap.find(Name);
-    if (It != ProfileDataMap.end())
-      if (It->second.RegionCounters)
-        continue;
-
     // Move the name variable to the right section.
     Name->setSection(getNameSection());
     Name->setAlignment(1);