Rename CountingFunctionInserter and use for both mcount and cygprofile calls, before and after inlining

Clang implements the -finstrument-functions flag inherited from GCC, which
inserts calls to __cyg_profile_func_{enter,exit} on function entry and exit.

This is useful for getting a trace of how the functions in a program are
executed. Normally, the calls remain even if a function is inlined into another
function, but it is useful to be able to turn this off for users who are
interested in a lower-level trace, i.e. one that reflects what functions are
called post-inlining. (We use this to generate link order files for Chromium.)

LLVM already has a pass for inserting similar instrumentation calls to
mcount(), which it does after inlining. This patch renames and extends that
pass to handle calls both to mcount and the cygprofile functions, before and/or
after inlining as controlled by function attributes.

Differential Revision: https://reviews.llvm.org/D39287

llvm-svn: 318195

1 files changed, 148 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp b/llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp
new file mode 100644
index 00000000000..ba6f67e15ca
--- /dev/null
+++ b/llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp
@@ -0,0 +1,148 @@
+//===- EntryExitInstrumenter.cpp - Function Entry/Exit Instrumentation ----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/EntryExitInstrumenter.h"
+#include "llvm/Analysis/GlobalsModRef.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/Scalar.h"
+using namespace llvm;
+
+static void insertCall(Function &CurFn, StringRef Func,
+                       Instruction *InsertionPt) {
+  Module &M = *InsertionPt->getParent()->getParent()->getParent();
+  LLVMContext &C = InsertionPt->getParent()->getContext();
+
+  if (Func == "mcount" ||
+      Func == ".mcount" ||
+      Func == "\01__gnu_mcount_nc" ||
+      Func == "\01_mcount" ||
+      Func == "\01mcount" ||
+      Func == "__mcount" ||
+      Func == "_mcount") {
+    Constant *Fn = M.getOrInsertFunction(Func, Type::getVoidTy(C));
+    CallInst::Create(Fn, "", InsertionPt);
+    return;
+  }
+
+  if (Func == "__cyg_profile_func_enter" || Func == "__cyg_profile_func_exit") {
+    Type *ArgTypes[] = {Type::getInt8PtrTy(C), Type::getInt8PtrTy(C)};
+
+    Constant *Fn = M.getOrInsertFunction(
+        Func, FunctionType::get(Type::getVoidTy(C), ArgTypes, false));
+
+    Instruction *RetAddr = CallInst::Create(
+        Intrinsic::getDeclaration(&M, Intrinsic::returnaddress),
+        ArrayRef<Value *>(ConstantInt::get(Type::getInt32Ty(C), 0)), "",
+        InsertionPt);
+
+    Value *Args[] = {ConstantExpr::getBitCast(&CurFn, Type::getInt8PtrTy(C)),
+                     RetAddr};
+
+    CallInst::Create(Fn, ArrayRef<Value *>(Args), "", InsertionPt);
+    return;
+  }
+
+  // We only know how to call a fixed set of instrumentation functions, because
+  // they all expect different arguments, etc.
+  report_fatal_error(Twine("Unknown instrumentation function: '") + Func + "'");
+}
+
+static bool runOnFunction(Function &F, bool PostInlining) {
+  StringRef EntryAttr = PostInlining ? "instrument-function-entry-inlined"
+                                     : "instrument-function-entry";
+
+  StringRef ExitAttr = PostInlining ? "instrument-function-exit-inlined"
+                                    : "instrument-function-exit";
+
+  StringRef EntryFunc = F.getFnAttribute(EntryAttr).getValueAsString();
+  StringRef ExitFunc = F.getFnAttribute(ExitAttr).getValueAsString();
+
+  bool Changed = false;
+
+  // If the attribute is specified, insert instrumentation and then "consume"
+  // the attribute so that it's not inserted again if the pass should happen to
+  // run later for some reason.
+
+  if (!EntryFunc.empty()) {
+    insertCall(F, EntryFunc, &*F.begin()->getFirstInsertionPt());
+    Changed = true;
+    F.removeAttribute(AttributeList::FunctionIndex, EntryAttr);
+  }
+
+  if (!ExitFunc.empty()) {
+    for (BasicBlock &BB : F) {
+      TerminatorInst *T = BB.getTerminator();
+      if (isa<ReturnInst>(T)) {
+        insertCall(F, ExitFunc, T);
+        Changed = true;
+      }
+    }
+    F.removeAttribute(AttributeList::FunctionIndex, ExitAttr);
+  }
+
+  return Changed;
+}
+
+namespace {
+struct EntryExitInstrumenter : public FunctionPass {
+  static char ID;
+  EntryExitInstrumenter() : FunctionPass(ID) {
+    initializeEntryExitInstrumenterPass(*PassRegistry::getPassRegistry());
+  }
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.addPreserved<GlobalsAAWrapperPass>();
+  }
+  bool runOnFunction(Function &F) override { return ::runOnFunction(F, false); }
+};
+char EntryExitInstrumenter::ID = 0;
+
+struct PostInlineEntryExitInstrumenter : public FunctionPass {
+  static char ID;
+  PostInlineEntryExitInstrumenter() : FunctionPass(ID) {
+    initializePostInlineEntryExitInstrumenterPass(
+        *PassRegistry::getPassRegistry());
+  }
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.addPreserved<GlobalsAAWrapperPass>();
+  }
+  bool runOnFunction(Function &F) override { return ::runOnFunction(F, true); }
+};
+char PostInlineEntryExitInstrumenter::ID = 0;
+}
+
+INITIALIZE_PASS(
+    EntryExitInstrumenter, "ee-instrument",
+    "Instrument function entry/exit with calls to e.g. mcount() (pre inlining)",
+    false, false);
+
+INITIALIZE_PASS(PostInlineEntryExitInstrumenter, "post-inline-ee-instrument",
+                "Instrument function entry/exit with calls to e.g. mcount() "
+                "(post inlining)",
+                false, false);
+
+FunctionPass *llvm::createEntryExitInstrumenterPass() {
+  return new EntryExitInstrumenter();
+}
+
+FunctionPass *llvm::createPostInlineEntryExitInstrumenterPass() {
+  return new PostInlineEntryExitInstrumenter();
+}
+
+PreservedAnalyses
+llvm::EntryExitInstrumenterPass::run(Function &F, FunctionAnalysisManager &AM) {
+  runOnFunction(F, PostInlining);
+  PreservedAnalyses PA;
+  PA.preserveSet<CFGAnalyses>();
+  return PA;
+}