Add a -finstrument-functions-size=n option to control basic block

filtering. If omitted entirely, the original behavior is restored.
This also undos the string and __pnacl_profile stuff from the previous
CL. Finally, it fixes and updates the -finstrument-function tests.

BUG=none
R=bradnelson@google.com, dschuff@chromium.org

Review URL: https://codereview.chromium.org/19793007

1 files changed, 16 insertions, 6 deletions

diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp
index 75c60edbba..a3c39649b7 100644
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/lib/CodeGen/CodeGenFunction.cpp
@@ -222,8 +222,18 @@ void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
   // Emit function epilog (to return).
   EmitReturnBlock();
 
-  if (ShouldInstrumentFunction())
-    EmitFunctionInstrumentation("__cyg_profile_func_exit");
+  if (ShouldInstrumentFunction()) {
+      // The size of the function isn't known during StartFunction, so in order
+      // to instrument selectively based on function size, we need to wait
+      // until the end and insert both the entry and exit instrumentation
+      llvm::BasicBlock *CurBlock = Builder.GetInsertBlock();
+      llvm::BasicBlock *BeginBlock = &CurFn->getEntryBlock();
+
+      Builder.SetInsertPoint(BeginBlock, BeginBlock->begin());
+      EmitFunctionInstrumentation("__cyg_profile_func_enter");
+      Builder.SetInsertPoint(CurBlock);
+      EmitFunctionInstrumentation("__cyg_profile_func_exit");
+  }
 
   // Emit debug descriptor for function end.
   if (CGDebugInfo *DI = getDebugInfo()) {
@@ -274,7 +284,10 @@ bool CodeGenFunction::ShouldInstrumentFunction() {
     return false;
   if (!CurFuncDecl || CurFuncDecl->hasAttr<NoInstrumentFunctionAttr>())
     return false;
-  return true;
+
+  // If not specified, defaults to 0.
+  int Size = CGM.getCodeGenOpts().InstrumentFunctionsSize;
+  return CurFn->getBasicBlockList().size() >= Size;
 }
 
 /// EmitFunctionInstrumentation - Emit LLVM code to call the specified
@@ -541,9 +554,6 @@ void CodeGenFunction::StartFunction(GlobalDecl GD,
     DI->EmitFunctionStart(GD, FnType, CurFn, Builder);
   }
 
-  if (ShouldInstrumentFunction())
-    EmitFunctionInstrumentation("__cyg_profile_func_enter");
-
   if (CGM.getCodeGenOpts().InstrumentForProfiling)
     EmitMCountInstrumentation();