Explicitly promote indirect calls before sample profile annotation.

Summary: In iterative sample pgo where profile is collected from PGOed binary, we may see indirect call targets promoted and inlined in the profile. Before profile annotation, we need to make this happen in order to annotate correctly on IR. This patch explicitly promotes these indirect calls and inlines them before profile annotation.

Reviewers: xur, davidxl

Reviewed By: davidxl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D29040

llvm-svn: 293657

lib/Transforms/IPO/SampleProfile.cpp

@@ -52,6 +52,7 @@
 #include "llvm/Support/Format.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/IPO.h"
+#include "llvm/Transforms/Instrumentation.h"
 #include "llvm/Transforms/Utils/Cloning.h"
 #include <cctype>
 
@@ -614,14 +615,14 @@ SampleProfileLoader::findFunctionSamples(const Instruction &Inst) const {
 /// Iteratively traverse all callsites of the function \p F, and find if
 /// the corresponding inlined instance exists and is hot in profile. If
 /// it is hot enough, inline the callsites and adds new callsites of the
-/// callee into the caller.
-///
-/// TODO: investigate the possibility of not invoking InlineFunction directly.
+/// callee into the caller. If the call is an indirect call, first promote
+/// it to direct call. Each indirect call is limited with a single target.
 ///
 /// \param F function to perform iterative inlining.
 ///
 /// \returns True if there is any inline happened.
 bool SampleProfileLoader::inlineHotFunctions(Function &F) {
+  DenseSet<Instruction *> PromotedInsns;
   bool Changed = false;
   LLVMContext &Ctx = F.getContext();
   std::function<AssumptionCache &(Function &)> GetAssumptionCache = [&](
@@ -647,10 +648,28 @@ bool SampleProfileLoader::inlineHotFunctions(Function &F) {
     }
     for (auto I : CIS) {
       InlineFunctionInfo IFI(nullptr, ACT ? &GetAssumptionCache : nullptr);
-      CallSite CS(I);
-      Function *CalledFunction = CS.getCalledFunction();
+      Function *CalledFunction = CallSite(I).getCalledFunction();
+      Instruction *DI = I;
+      if (!CalledFunction && !PromotedInsns.count(I)) {
+        auto CalleeFunctionName = findCalleeFunctionSamples(*I)->getName();
+        const char *Reason = "Callee function not available";
+        CalledFunction = F.getParent()->getFunction(CalleeFunctionName);
+        if (CalledFunction && isLegalToPromote(I, CalledFunction, &Reason)) {
+          // The indirect target was promoted and inlined in the profile, as a
+          // result, we do not have profile info for the branch probability.
+          // We set the probability to 80% taken to indicate that the static
+          // call is likely taken.
+          DI = promoteIndirectCall(I, CalledFunction, 80, 100);
+          PromotedInsns.insert(I);
+        } else {
+          DEBUG(dbgs() << "\nFailed to promote indirect call to "
+                       << CalleeFunctionName << " because " << Reason << "\n");
+          continue;
+        }
+      }
       if (!CalledFunction || !CalledFunction->getSubprogram())
         continue;
+      CallSite CS(DI);
       DebugLoc DLoc = I->getDebugLoc();
       uint64_t NumSamples = findCalleeFunctionSamples(*I)->getTotalSamples();
       if (InlineFunction(CS, IFI)) {

test/Transforms/SampleProfile/Inputs/indirect-call.prof

@@ -1,2 +1,8 @@
 test:63067:0
  4: 3345 _Z3barv:1398 _Z3foov:2059
+test_inline:3000:0
+ 5: foo_inline:3000
+  1: 3000
+test_noinline:3000:0
+ 5: foo_noinline:3000
+  1: 3000

test/Transforms/SampleProfile/indirect-call.ll

@@ -1,5 +1,6 @@
 ; RUN: opt < %s -sample-profile -sample-profile-file=%S/Inputs/indirect-call.prof -S | FileCheck %s
 
+; CHECK-LABEL: @test
 define void @test(void ()*) !dbg !3 {
   %2 = alloca void ()*
   store void ()* %0, void ()** %2
@@ -9,6 +10,41 @@ define void @test(void ()*) !dbg !3 {
   ret void
 }
 
+; CHECK-LABEL: @test_inline
+; If the indirect call is promoted and inlined in profile, we should promote and inline it.
+define void @test_inline(void ()*) !dbg !3 {
+  %2 = alloca void ()*
+  store void ()* %0, void ()** %2
+  %3 = load void ()*, void ()** %2
+; CHECK: icmp {{.*}} @foo_inline
+; CHECK: if.true.direct_targ:
+; CHECK-NOT: call
+; CHECK: if.false.orig_indirect:
+; CHECK: call
+  call void %3(), !dbg !5
+  ret void
+}
+
+; CHECK-LABEL: @test_noinline
+; If the indirect call target is not available, we should not promote it.
+define void @test_noinline(void ()*) !dbg !3 {
+  %2 = alloca void ()*
+  store void ()* %0, void ()** %2
+  %3 = load void ()*, void ()** %2
+; CHECK-NOT: icmp
+; CHECK: call
+  call void %3(), !dbg !5
+  ret void
+}
+
+define void @foo_inline() !dbg !3 {
+  ret void
+}
+
+define i32 @foo_noinline(i32 %x) !dbg !3 {
+  ret i32 %x
+}
+
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!2}
 
@@ -17,4 +53,5 @@ define void @test(void ()*) !dbg !3 {
 !2 = !{i32 2, !"Debug Info Version", i32 3}
 !3 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 1, unit: !0)
 !4 = !DILocation(line: 5, scope: !3)
+!5 = !DILocation(line: 6, scope: !3)
 ; CHECK: ![[PROF]] = !{!"VP", i32 0, i64 3457, i64 9191153033785521275, i64 2059, i64 -1069303473483922844, i64 1398}