[compiler-rt] [llvm] [InstrPGO][TypeProf]Annotate vtable types when they are present in the profile (PR #99402)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-pgo

Author: Mingming Liu (minglotus-6)

<details>
<summary>Changes</summary>

Before this change, when `file.profdata` have vtable profiles but `--enable-vtable-value-profiling` is not on for optimized build, warnings [from this line](https://github.com/llvm/llvm-project/blob/464d321ee8dde1eaf14b5537eaf030e6df513849/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp#L1762-L1768) will show up. They are benign for performance but confusing.

It's better to automatically annotate vtable profiles if `file.profdata` has them. This change implements it in `pgo-instr-use` pass.
* If `--enable-vtable-profile-use` is explicitly set to false in the command line, vtable profiles won't be annotated.


---
Full diff: https://github.com/llvm/llvm-project/pull/99402.diff


2 Files Affected:

- (modified) compiler-rt/test/profile/Linux/instrprof-vtable-value-prof.cpp (+24-4) 
- (modified) llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp (+14-2) 


``````````diff
diff --git a/compiler-rt/test/profile/Linux/instrprof-vtable-value-prof.cpp b/compiler-rt/test/profile/Linux/instrprof-vtable-value-prof.cpp
index 24a96a227393a..83ceb9b0cf556 100644
--- a/compiler-rt/test/profile/Linux/instrprof-vtable-value-prof.cpp
+++ b/compiler-rt/test/profile/Linux/instrprof-vtable-value-prof.cpp
@@ -109,6 +109,26 @@
 // ICTEXT: {{.*}}instrprof-vtable-value-prof.cpp;_ZTVN12_GLOBAL__N_18Derived2E:750
 // ICTEXT: _ZTV8Derived1:250
 
+// When vtable value profiles exist, pgo-instr-use pass should annotate them
+// even if `-enable-vtable-value-profiling` is not explicitly on.
+// RUN: %clangxx -m64 -fprofile-use=test.profdata -fuse-ld=lld -O2 \
+// RUN:   -mllvm -print-after=pgo-instr-use -mllvm -filter-print-funcs=main \
+// RUN:   -mllvm -print-module-scope %s 2>&1 | FileCheck %s --check-prefix=ANNOTATE
+
+// ANNOTATE-NOT: Inconsistent number of value sites
+// ANNOTATE: !{!"VP", i32 2
+
+// When vtable value profiles exist, pgo-instr-use pass will not annotate them
+// if `-enable-vtable-profile-use` is explicitly set to false to discard vtable
+// value profiles.
+// RUN: %clangxx -m64 -fprofile-use=test.profdata -fuse-ld=lld -O2 \
+// RUN:   -mllvm -enable-vtable-profile-use=false -mllvm -print-after=pgo-instr-use \
+// RUN:   -mllvm -filter-print-funcs=main -mllvm -print-module-scope %s 2>&1 | \
+// RUN:   FileCheck %s --check-prefix=OMIT
+
+// OMIT: Inconsistent number of value sites
+// OMIT-NOT: !{!"VP", i32 2
+
 // Test indirect call promotion transformation using vtable profiles.
 // - Build with `-g` to enable debug information.
 // - In real world settings, ICP pass is disabled in prelink pipeline. In
@@ -128,12 +148,12 @@
 // RUN:    | FileCheck %s --check-prefixes=REMARK,IR --implicit-check-not="!VP"
 
 // For the indirect call site `ptr->func`
-// REMARK: instrprof-vtable-value-prof.cpp:205:19: Promote indirect call to _ZN12_GLOBAL__N_18Derived24funcEii with count 150 out of 200, sink 1 instruction(s) and compare 1 vtable(s): {_ZTVN12_GLOBAL__N_18Derived2E}
-// REMARK: instrprof-vtable-value-prof.cpp:205:19: Promote indirect call to _ZN8Derived14funcEii with count 50 out of 50, sink 1 instruction(s) and compare 1 vtable(s): {_ZTV8Derived1}
+// REMARK: instrprof-vtable-value-prof.cpp:227:19: Promote indirect call to _ZN12_GLOBAL__N_18Derived24funcEii with count 150 out of 200, sink 1 instruction(s) and compare 1 vtable(s): {_ZTVN12_GLOBAL__N_18Derived2E}
+// REMARK: instrprof-vtable-value-prof.cpp:227:19: Promote indirect call to _ZN8Derived14funcEii with count 50 out of 50, sink 1 instruction(s) and compare 1 vtable(s): {_ZTV8Derived1}
 //
 // For the indirect call site `delete ptr`
-// REMARK: instrprof-vtable-value-prof.cpp:207:5: Promote indirect call to _ZN12_GLOBAL__N_18Derived2D0Ev with count 750 out of 1000, sink 2 instruction(s) and compare 1 vtable(s): {_ZTVN12_GLOBAL__N_18Derived2E}
-// REMARK: instrprof-vtable-value-prof.cpp:207:5: Promote indirect call to _ZN8Derived1D0Ev with count 250 out of 250, sink 2 instruction(s) and compare 1 vtable(s): {_ZTV8Derived1}
+// REMARK: instrprof-vtable-value-prof.cpp:229:5: Promote indirect call to _ZN12_GLOBAL__N_18Derived2D0Ev with count 750 out of 1000, sink 2 instruction(s) and compare 1 vtable(s): {_ZTVN12_GLOBAL__N_18Derived2E}
+// REMARK: instrprof-vtable-value-prof.cpp:229:5: Promote indirect call to _ZN8Derived1D0Ev with count 250 out of 250, sink 2 instruction(s) and compare 1 vtable(s): {_ZTV8Derived1}
 
 // The IR matchers for indirect callsite `ptr->func`.
 // IR-LABEL: @main
diff --git a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
index 35b1bbf21be97..2baca05988808 100644
--- a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
@@ -1096,7 +1096,7 @@ class PGOUseFunc {
       : F(Func), M(Modu), BFI(BFIin), PSI(PSI),
         FuncInfo(Func, TLI, ComdatMembers, false, BPI, BFIin, IsCS,
                  InstrumentFuncEntry, HasSingleByteCoverage),
-        FreqAttr(FFA_Normal), IsCS(IsCS) {}
+        FreqAttr(FFA_Normal), IsCS(IsCS), VPC(Func, TLI) {}
 
   void handleInstrProfError(Error Err, uint64_t MismatchedFuncSum);
 
@@ -1178,6 +1178,8 @@ class PGOUseFunc {
   // Is to use the context sensitive profile.
   bool IsCS;
 
+  ValueProfileCollector VPC;
+
   // Find the Instrumented BB and set the value. Return false on error.
   bool setInstrumentedCounts(const std::vector<uint64_t> &CountFromProfile);
 
@@ -1755,8 +1757,18 @@ void PGOUseFunc::annotateValueSites() {
 void PGOUseFunc::annotateValueSites(uint32_t Kind) {
   assert(Kind <= IPVK_Last);
   unsigned ValueSiteIndex = 0;
-  auto &ValueSites = FuncInfo.ValueSites[Kind];
   unsigned NumValueSites = ProfileRecord.getNumValueSites(Kind);
+  // FuncPGOInstrumentation ctor finds value sites for each kind. It runs on the
+  // common path of pgo-instr-gen and pgo-instr-use, and vtable kind path
+  // is gated by `-enable-vtable-value-profiling`. If vtable profiles are
+  // present, not explicitly discarded and vtable sites remain empty, try to
+  // find the sites again.
+  if (NumValueSites > 0 && Kind == IPVK_VTableTarget &&
+      FuncInfo.ValueSites[Kind].empty() &&
+      !(EnableVTableProfileUse.getNumOccurrences() &&
+        EnableVTableProfileUse == false))
+    FuncInfo.ValueSites[IPVK_VTableTarget] = VPC.get(IPVK_VTableTarget);
+  auto &ValueSites = FuncInfo.ValueSites[Kind];
   if (NumValueSites != ValueSites.size()) {
     auto &Ctx = M->getContext();
     Ctx.diagnose(DiagnosticInfoPGOProfile(

``````````

</details>


https://github.com/llvm/llvm-project/pull/99402