[llvm] r257091 - [PGO] Simplify coverage mapping lowering

[Xinliang David Li via llvm-commits]

Author: davidxl
Date: Thu Jan  7 14:05:49 2016
New Revision: 257091

URL: http://llvm.org/viewvc/llvm-project?rev=257091&view=rev
Log:
[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.


Modified:
    llvm/trunk/include/llvm/ProfileData/InstrProf.h
    llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp

Modified: llvm/trunk/include/llvm/ProfileData/InstrProf.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ProfileData/InstrProf.h?rev=257091&r1=257090&r2=257091&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ProfileData/InstrProf.h (original)
+++ llvm/trunk/include/llvm/ProfileData/InstrProf.h Thu Jan  7 14:05:49 2016
@@ -89,6 +89,12 @@ inline StringRef getCoverageMappingVarNa
   return "__llvm_coverage_mapping";
 }
 
+/// Return the name of the internal variable recording the array
+/// of PGO name vars referenced by the coverage mapping, The owning
+/// functions of those names are not emitted by FE (e.g, unused inline
+/// functions.)
+inline StringRef getCoverageNamesVarName() { return "__llvm_coverage_names"; }
+
 /// Return the name of function that registers all the per-function control
 /// data at program startup time by calling __llvm_register_function. This
 /// function has internal linkage and is called by  __llvm_profile_init

Modified: llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp?rev=257091&r1=257090&r2=257091&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp Thu Jan  7 14:05:49 2016
@@ -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
         }
       }
 
-  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(Inst
   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);