[PATCH] D15852: [PGO]: Simplify coverage data lowering code

[David Li via llvm-commits]

davidxl updated this revision to Diff 44235.
davidxl added a comment.

Update comments. Further improve efficiency by skipping redundant map lookup (unused functions are guaranteed to be not in the map). With recent updates, the patch will now improve overall compile time with coverage mapping turned on.


http://reviews.llvm.org/D15852

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

Index: lib/Transforms/Instrumentation/InstrProfiling.cpp
===================================================================
--- lib/Transforms/Instrumentation/InstrProfiling.cpp
+++ lib/Transforms/Instrumentation/InstrProfiling.cpp
@@ -93,8 +93,8 @@
   /// 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 @@
         }
       }
 
-  if (GlobalVariable *Coverage =
-          M.getNamedGlobal(getCoverageMappingVarName())) {
-    lowerCoverageData(Coverage);
+  if (GlobalVariable *CoverageNamesVar =
+          M.getNamedGlobal(getCoverageNamesVarName())) {
+    lowerCoverageData(CoverageNamesVar);
     MadeChange = true;
   }
 
@@ -233,28 +233,16 @@
   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);
Index: include/llvm/ProfileData/InstrProf.h
===================================================================
--- include/llvm/ProfileData/InstrProf.h
+++ include/llvm/ProfileData/InstrProf.h
@@ -89,6 +89,10 @@
   return "__llvm_coverage_mapping";
 }
 
+/// Return the name of the internal variable recording the array
+/// of pgo function name vars referenced by the coverage mapping.
+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


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