[ctx_prof] Add analysis utility to fetch ID of a callsite (#104491)

This will be needed when maintaining the contextual profile for ICP or inlining - we'll need to first fetch the ID of a callsite, which is in an instrumentation instruction (intrinsic) preceding the callsite.

Author: mtrofin

llvm/include/llvm/Analysis/CtxProfAnalysis.h

@@ -9,6 +9,8 @@
 #ifndef LLVM_ANALYSIS_CTXPROFANALYSIS_H
 #define LLVM_ANALYSIS_CTXPROFANALYSIS_H
 
+#include "llvm/IR/InstrTypes.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/ProfileData/PGOCtxProfReader.h"
 
@@ -82,6 +84,8 @@ class CtxProfAnalysis : public AnalysisInfoMixin<CtxProfAnalysis> {
   using Result = PGOContextualProfile;
 
   PGOContextualProfile run(Module &M, ModuleAnalysisManager &MAM);
+
+  static InstrProfCallsite *getCallsiteInstrumentation(CallBase &CB);
 };
 
 class CtxProfAnalysisPrinterPass

llvm/lib/Analysis/CtxProfAnalysis.cpp

@@ -186,3 +186,10 @@ PreservedAnalyses CtxProfAnalysisPrinterPass::run(Module &M,
   OS << "\n";
   return PreservedAnalyses::all();
 }
+
+InstrProfCallsite *CtxProfAnalysis::getCallsiteInstrumentation(CallBase &CB) {
+  while (auto *Prev = CB.getPrevNode())
+    if (auto *IPC = dyn_cast<InstrProfCallsite>(Prev))
+      return IPC;
+  return nullptr;
+}

llvm/unittests/Analysis/CMakeLists.txt

@@ -22,6 +22,7 @@ set(ANALYSIS_TEST_SOURCES
   CFGTest.cpp
   CGSCCPassManagerTest.cpp
   ConstraintSystemTest.cpp
+  CtxProfAnalysisTest.cpp
   DDGTest.cpp
   DomTreeUpdaterTest.cpp
   DXILResourceTest.cpp

llvm/unittests/Analysis/CtxProfAnalysisTest.cpp

@@ -0,0 +1,135 @@
+//===--- CtxProfAnalysisTest.cpp ------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/CtxProfAnalysis.h"
+#include "llvm/Analysis/BlockFrequencyInfo.h"
+#include "llvm/Analysis/BranchProbabilityInfo.h"
+#include "llvm/Analysis/CGSCCPassManager.h"
+#include "llvm/Analysis/LoopAnalysisManager.h"
+#include "llvm/AsmParser/Parser.h"
+#include "llvm/IR/Analysis.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassInstrumentation.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/Passes/PassBuilder.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/Transforms/Instrumentation/PGOInstrumentation.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+class CtxProfAnalysisTest : public testing::Test {
+  static constexpr auto *IR = R"IR(
+declare void @bar()
+
+define private void @foo(i32 %a, ptr %fct) #0 !guid !0 {
+  %t = icmp eq i32 %a, 0
+  br i1 %t, label %yes, label %no
+yes:
+  call void %fct(i32 %a)
+  br label %exit
+no:
+  call void @bar()
+  br label %exit
+exit:
+  ret void
+}
+
+define void @an_entrypoint(i32 %a) {
+  %t = icmp eq i32 %a, 0
+  br i1 %t, label %yes, label %no
+
+yes:
+  call void @foo(i32 1, ptr null)
+  ret void
+no:
+  ret void
+}
+
+define void @another_entrypoint_no_callees(i32 %a) {
+  %t = icmp eq i32 %a, 0
+  br i1 %t, label %yes, label %no
+
+yes:
+  ret void
+no:
+  ret void
+}
+
+attributes #0 = { noinline }
+!0 = !{ i64 11872291593386833696 }
+)IR";
+
+protected:
+  LLVMContext C;
+  PassBuilder PB;
+  ModuleAnalysisManager MAM;
+  FunctionAnalysisManager FAM;
+  CGSCCAnalysisManager CGAM;
+  LoopAnalysisManager LAM;
+  std::unique_ptr<Module> M;
+
+  void SetUp() override {
+    SMDiagnostic Err;
+    M = parseAssemblyString(IR, Err, C);
+    ASSERT_TRUE(!!M);
+  }
+
+public:
+  CtxProfAnalysisTest() {
+    PB.registerModuleAnalyses(MAM);
+    PB.registerCGSCCAnalyses(CGAM);
+    PB.registerFunctionAnalyses(FAM);
+    PB.registerLoopAnalyses(LAM);
+    PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
+  }
+};
+
+TEST_F(CtxProfAnalysisTest, GetCallsiteIDTest) {
+  ModulePassManager MPM;
+  MPM.addPass(PGOInstrumentationGen(PGOInstrumentationType::CTXPROF));
+  EXPECT_FALSE(MPM.run(*M, MAM).areAllPreserved());
+  auto *F = M->getFunction("foo");
+  ASSERT_NE(F, nullptr);
+  std::vector<uint32_t> InsValues;
+
+  for (auto &BB : *F)
+    for (auto &I : BB)
+      if (auto *CB = dyn_cast<CallBase>(&I)) {
+        // Skip instrumentation inserted intrinsics.
+        if (CB->getCalledFunction() && CB->getCalledFunction()->isIntrinsic())
+          continue;
+        auto *Ins = CtxProfAnalysis::getCallsiteInstrumentation(*CB);
+        ASSERT_NE(Ins, nullptr);
+        InsValues.push_back(Ins->getIndex()->getZExtValue());
+      }
+
+  EXPECT_THAT(InsValues, testing::ElementsAre(0, 1));
+}
+
+TEST_F(CtxProfAnalysisTest, GetCallsiteIDNegativeTest) {
+  auto *F = M->getFunction("foo");
+  ASSERT_NE(F, nullptr);
+  CallBase *FirstCall = nullptr;
+  for (auto &BB : *F)
+    for (auto &I : BB)
+      if (auto *CB = dyn_cast<CallBase>(&I)) {
+        if (CB->isIndirectCall() || !CB->getCalledFunction()->isIntrinsic()) {
+          FirstCall = CB;
+          break;
+        }
+      }
+  ASSERT_NE(FirstCall, nullptr);
+  auto *IndIns = CtxProfAnalysis::getCallsiteInstrumentation(*FirstCall);
+  EXPECT_EQ(IndIns, nullptr);
+}
+
+} // namespace