[MemProf] Merge all callee guids for indirect call VP metadata

When matching memprof profiles, for indirect calls we use the callee
guids recorded on callsites in the profile to synthesize indirect call
VP metadata when none exists. However, we only do this for the first
matching CallSiteEntry from the profile.

In some case there can be multiple, for example when the current
function was eventually inlined into multiple callers. Profile
generation propagates the CallSiteEntry from those callers into the
inlined callee's profile as it may not yet have been inlined in the
new compile.

To capture all of these potential indirect call targets, merge callee
guids across all matching CallSiteEntries.

Author: teresajohnson

llvm/lib/Transforms/Instrumentation/MemProfUse.cpp

@@ -528,35 +528,50 @@ static void handleCallSite(
     Module &M, std::set<std::vector<uint64_t>> &MatchedCallSites,
     OptimizationRemarkEmitter &ORE) {
   auto &Ctx = M.getContext();
+  // Set of Callee GUIDs to attach to indirect calls. We accumulate all of them
+  // to support cases where the instuction's inlined frames match multiple call
+  // site entries, which can happen if the profile was collected from a binary
+  // where this instruction was eventually inlined into multiple callers.
+  SetVector<GlobalValue::GUID> CalleeGuids;
+  bool CallsiteMDAdded = false;
   for (const auto &CallSiteEntry : CallSiteEntries) {
     // If we found and thus matched all frames on the call, create and
     // attach call stack metadata.
     if (stackFrameIncludesInlinedCallStack(CallSiteEntry.Frames,
                                            InlinedCallStack)) {
       NumOfMemProfMatchedCallSites++;
-      addCallsiteMetadata(I, InlinedCallStack, Ctx);
-
-      // Try to attach indirect call metadata if possible.
-      if (!CalledFunction)
-        addVPMetadata(M, I, CallSiteEntry.CalleeGuids);
-
       // Only need to find one with a matching call stack and add a single
       // callsite metadata.
-
-      // Accumulate call site matching information upon request.
-      if (ClPrintMemProfMatchInfo) {
-        std::vector<uint64_t> CallStack;
-        append_range(CallStack, InlinedCallStack);
-        MatchedCallSites.insert(std::move(CallStack));
+      if (!CallsiteMDAdded) {
+        addCallsiteMetadata(I, InlinedCallStack, Ctx);
+
+        // Accumulate call site matching information upon request.
+        if (ClPrintMemProfMatchInfo) {
+          std::vector<uint64_t> CallStack;
+          append_range(CallStack, InlinedCallStack);
+          MatchedCallSites.insert(std::move(CallStack));
+        }
+        ORE.emit(OptimizationRemark(DEBUG_TYPE, "MemProfUse", &I)
+                 << ore::NV("CallSite", &I) << " in function "
+                 << ore::NV("Caller", I.getFunction())
+                 << " matched callsite with frame count "
+                 << ore::NV("Frames", InlinedCallStack.size()));
+
+        // If this is a direct call, we're done.
+        if (CalledFunction)
+          break;
+        CallsiteMDAdded = true;
       }
-      ORE.emit(OptimizationRemark(DEBUG_TYPE, "MemProfUse", &I)
-               << ore::NV("CallSite", &I) << " in function "
-               << ore::NV("Caller", I.getFunction())
-               << " matched callsite with frame count "
-               << ore::NV("Frames", InlinedCallStack.size()));
-      break;
+
+      assert(!CalledFunction && "Didn't expect direct call");
+
+      // Collect Callee GUIDs from all matching CallSiteEntries.
+      CalleeGuids.insert(CallSiteEntry.CalleeGuids.begin(),
+                         CallSiteEntry.CalleeGuids.end());
     }
   }
+  // Try to attach indirect call metadata if possible.
+  addVPMetadata(M, I, CalleeGuids.getArrayRef());
 }
 
 static void readMemprof(Module &M, Function &F,

llvm/test/Transforms/PGOProfile/memprof_annotate_indirect_call.test

@@ -18,6 +18,18 @@ HeapProfileRecords:
       - Frames:
           - { Function: _Z3barv, LineOffset: 3, Column: 5, IsInlineFrame: false }
         CalleeGuids:   [0x123456789abcdef0, 0x23456789abcdef01]
+      # The next 2 sets of frames simulates the case where this function was
+      # eventually inlined into multiple callers. We would have propagated the
+      # resulting frames and callee guids here for matching with they not yet
+      # inlined bar. We should aggregate all callee guids into the metadata.
+      - Frames:
+          - { Function: _Z3barv, LineOffset: 3, Column: 5, IsInlineFrame: true }
+          - { Function: _Z3foov, LineOffset: 1, Column: 6, IsInlineFrame: false }
+        CalleeGuids:   [0x1234, 0x2345]
+      - Frames:
+          - { Function: _Z3barv, LineOffset: 3, Column: 5, IsInlineFrame: true }
+          - { Function: _Z3foov, LineOffset: 10, Column: 7, IsInlineFrame: false }
+        CalleeGuids:   [0x3456, 0x4567]
 ...
 
 ;--- basic.ll
@@ -31,7 +43,7 @@ entry:
   ret void
 }
 
-; CHECK-ENABLE: !6 = !{!"VP", i32 0, i64 2, i64 1311768467463790320, i64 1, i64 2541551405711093505, i64 1}
+; CHECK-ENABLE: !6 = !{!"VP", i32 0, i64 6, i64 13398, i64 1, i64 17767, i64 1, i64 4660, i64 1, i64 9029, i64 1, i64 1311768467463790320, i64 1, i64 2541551405711093505, i64 1}
 
 !llvm.module.flags = !{!2, !3}