[BOLT] Support pre-aggregated returns

bolt/include/bolt/Profile/DataAggregator.h

@@ -99,16 +99,17 @@ class DataAggregator : public DataReader {
     uint64_t Addr;
   };
 
-  /// Container for the unit of branch data.
-  /// Backwards compatible with legacy use for branches and fall-throughs:
-  /// - if \p Branch is FT_ONLY or FT_EXTERNAL_ORIGIN, the trace only
-  ///   contains fall-through data,
-  /// - if \p To is BR_ONLY, the trace only contains branch data.
+  /// Container for the unit of branch data, matching pre-aggregated trace type.
+  /// Backwards compatible with branch and fall-through types:
+  /// - if \p To is < 0, the trace only contains branch data (BR_ONLY),
+  /// - if \p Branch is < 0, the trace only contains fall-through data
+  ///   (FT_ONLY, FT_EXTERNAL_ORIGIN, or FT_EXTERNAL_RETURN).
   struct Trace {
     static constexpr const uint64_t EXTERNAL = 0ULL;
     static constexpr const uint64_t BR_ONLY = -1ULL;
     static constexpr const uint64_t FT_ONLY = -1ULL;
     static constexpr const uint64_t FT_EXTERNAL_ORIGIN = -2ULL;
+    static constexpr const uint64_t FT_EXTERNAL_RETURN = -3ULL;
 
     uint64_t Branch;
     uint64_t From;
@@ -388,9 +389,9 @@ class DataAggregator : public DataReader {
   /// File format syntax:
   /// E <event>
   /// S <start> <count>
-  /// T <start> <end> <ft_end> <count>
+  /// [TR] <start> <end> <ft_end> <count>
   /// B <start> <end> <count> <mispred_count>
-  /// [Ff] <start> <end> <count>
+  /// [Ffr] <start> <end> <count>
   ///
   /// where <start>, <end>, <ft_end> have the format [<id>:]<offset>
   ///
@@ -401,8 +402,11 @@ class DataAggregator : public DataReader {
   /// f - an aggregated fall-through with external origin - used to disambiguate
   ///       between a return hitting a basic block head and a regular internal
   ///       jump to the block
+  /// r - an aggregated fall-through originating at an external return, no
+  ///       checks are performed for a fallthrough start
   /// T - an aggregated trace: branch from <start> to <end> with a fall-through
   ///       to <ft_end>
+  /// R - an aggregated trace originating at a return
   ///
   /// <id> - build id of the object containing the address. We can skip it for
   /// the main binary and use "X" for an unknown object. This will save some
@@ -530,7 +534,12 @@ inline raw_ostream &operator<<(raw_ostream &OS,
                                const DataAggregator::Trace &T) {
   switch (T.Branch) {
   case DataAggregator::Trace::FT_ONLY:
+    break;
   case DataAggregator::Trace::FT_EXTERNAL_ORIGIN:
+    OS << "X:0 -> ";
+    break;
+  case DataAggregator::Trace::FT_EXTERNAL_RETURN:
+    OS << "X:R -> ";
     break;
   default:
     OS << Twine::utohexstr(T.Branch) << " -> ";

bolt/lib/Profile/DataAggregator.cpp

@@ -524,8 +524,7 @@ Error DataAggregator::preprocessProfile(BinaryContext &BC) {
 
 heatmap:
   // Sort parsed traces for faster processing.
-  if (!opts::BasicAggregation)
-    llvm::sort(Traces, llvm::less_first());
+  llvm::sort(Traces, llvm::less_first());
 
   if (!opts::HeatmapMode)
     return Error::success();
@@ -870,13 +869,9 @@ DataAggregator::getFallthroughsInTrace(BinaryFunction &BF, const Trace &Trace,
 
   // Adjust FromBB if the first LBR is a return from the last instruction in
   // the previous block (that instruction should be a call).
-  if (IsReturn) {
-    if (From)
-      FromBB = BF.getBasicBlockContainingOffset(From - 1);
-    else
-      LLVM_DEBUG(dbgs() << "return to the function start: " << Trace << '\n');
-  } else if (Trace.Branch == Trace::EXTERNAL && From == FromBB->getOffset() &&
-             !FromBB->isEntryPoint() && !FromBB->isLandingPad()) {
+  if (Trace.Branch != Trace::FT_ONLY && !BF.containsAddress(Trace.Branch) &&
+      From == FromBB->getOffset() &&
+      (IsReturn ? From : !(FromBB->isEntryPoint() || FromBB->isLandingPad()))) {
     const BinaryBasicBlock *PrevBB =
         BF.getLayout().getBlock(FromBB->getIndex() - 1);
     if (PrevBB->getSuccessor(FromBB->getLabel())) {
@@ -1202,12 +1197,14 @@ ErrorOr<Location> DataAggregator::parseLocationOrOffset() {
 std::error_code DataAggregator::parseAggregatedLBREntry() {
   enum AggregatedLBREntry : char {
     INVALID = 0,
-    EVENT_NAME,        // E
-    TRACE,             // T
-    SAMPLE,            // S
-    BRANCH,            // B
-    FT,                // F
-    FT_EXTERNAL_ORIGIN // f
+    EVENT_NAME,         // E
+    TRACE,              // T
+    RETURN,             // R
+    SAMPLE,             // S
+    BRANCH,             // B
+    FT,                 // F
+    FT_EXTERNAL_ORIGIN, // f
+    FT_EXTERNAL_RETURN  // r
   } Type = INVALID;
 
   /// The number of fields to parse, set based on \p Type.
@@ -1235,20 +1232,22 @@ std::error_code DataAggregator::parseAggregatedLBREntry() {
 
     Type = StringSwitch<AggregatedLBREntry>(Str)
                .Case("T", TRACE)
+               .Case("R", RETURN)
                .Case("S", SAMPLE)
                .Case("E", EVENT_NAME)
                .Case("B", BRANCH)
                .Case("F", FT)
                .Case("f", FT_EXTERNAL_ORIGIN)
+               .Case("r", FT_EXTERNAL_RETURN)
                .Default(INVALID);
 
     if (Type == INVALID) {
-      reportError("expected T, S, E, B, F or f");
+      reportError("expected T, R, S, E, B, F, f or r");
       return make_error_code(llvm::errc::io_error);
     }
 
     using SSI = StringSwitch<int>;
-    AddrNum = SSI(Str).Case("T", 3).Case("S", 1).Case("E", 0).Default(2);
+    AddrNum = SSI(Str).Cases("T", "R", 3).Case("S", 1).Case("E", 0).Default(2);
     CounterNum = SSI(Str).Case("B", 2).Case("E", 0).Default(1);
   }
 
@@ -1305,17 +1304,30 @@ std::error_code DataAggregator::parseAggregatedLBREntry() {
   if (ToFunc)
     ToFunc->setHasProfileAvailable();
 
-  /// For legacy fall-through types, adjust locations to match Trace container.
-  if (Type == FT || Type == FT_EXTERNAL_ORIGIN) {
+  /// For fall-through types, adjust locations to match Trace container.
+  if (Type == FT || Type == FT_EXTERNAL_ORIGIN || Type == FT_EXTERNAL_RETURN) {
     Addr[2] = Location(Addr[1]->Offset); // Trace To
     Addr[1] = Location(Addr[0]->Offset); // Trace From
-    // Put a magic value into Trace Branch to differentiate from a full trace.
-    Addr[0] = Location(Type == FT ? Trace::FT_ONLY : Trace::FT_EXTERNAL_ORIGIN);
+    // Put a magic value into Trace Branch to differentiate from a full trace:
+    if (Type == FT)
+      Addr[0] = Location(Trace::FT_ONLY);
+    else if (Type == FT_EXTERNAL_ORIGIN)
+      Addr[0] = Location(Trace::FT_EXTERNAL_ORIGIN);
+    else if (Type == FT_EXTERNAL_RETURN)
+      Addr[0] = Location(Trace::FT_EXTERNAL_RETURN);
+    else
+      llvm_unreachable("Unexpected fall-through type");
   }
 
-  /// For legacy branch type, mark Trace To to differentite from a full trace.
-  if (Type == BRANCH) {
+  /// For branch type, mark Trace To to differentiate from a full trace.
+  if (Type == BRANCH)
     Addr[2] = Location(Trace::BR_ONLY);
+
+  if (Type == RETURN) {
+    if (!Addr[0]->Offset)
+      Addr[0]->Offset = Trace::FT_EXTERNAL_RETURN;
+    else
+      Returns.emplace(Addr[0]->Offset);
   }
 
   /// Record a trace.
@@ -1565,6 +1577,7 @@ void DataAggregator::processBranchEvents() {
   NamedRegionTimer T("processBranch", "Processing branch events",
                      TimerGroupName, TimerGroupDesc, opts::TimeAggregator);
 
+  Returns.emplace(Trace::FT_EXTERNAL_RETURN);
   for (const auto &[Trace, Info] : Traces) {
     bool IsReturn = checkReturn(Trace.Branch);
     // Ignore returns.

bolt/test/X86/callcont-fallthru.s

@@ -10,6 +10,10 @@
 # RUN: link_fdata %s %t %t.pa-ret PREAGG-RET
 # Trace from an external location to a landing pad/entry point call continuation
 # RUN: link_fdata %s %t %t.pa-ext PREAGG-EXT
+# Return trace to a landing pad/entry point call continuation
+# RUN: link_fdata %s %t %t.pa-pret PREAGG-PRET
+# External return to a landing pad/entry point call continuation
+# RUN: link_fdata %s %t %t.pa-eret PREAGG-ERET
 # RUN-DISABLED: link_fdata %s %t %t.pa-plt PREAGG-PLT
 
 # RUN: llvm-strip --strip-unneeded %t -o %t.strip
@@ -38,6 +42,21 @@
 # RUN: llvm-bolt %t.strip --pa -p %t.pa-ext -o %t.out \
 # RUN:   --print-cfg --print-only=main | FileCheck %s --check-prefix=CHECK-SKIP
 
+## Check pre-aggregated return traces from external location attach call
+## continuation fallthrough count to secondary entry point (unstripped)
+# RUN: llvm-bolt %t --pa -p %t.pa-pret -o %t.out \
+# RUN:   --print-cfg --print-only=main | FileCheck %s --check-prefix=CHECK-ATTACH
+## Check pre-aggregated return traces from external location attach call
+## continuation fallthrough count to landing pad (stripped, landing pad)
+# RUN: llvm-bolt %t.strip --pa -p %t.pa-pret -o %t.out \
+# RUN:   --print-cfg --print-only=main | FileCheck %s --check-prefix=CHECK-ATTACH
+
+## Same for external return type
+# RUN: llvm-bolt %t --pa -p %t.pa-eret -o %t.out \
+# RUN:   --print-cfg --print-only=main | FileCheck %s --check-prefix=CHECK-ATTACH
+# RUN: llvm-bolt %t.strip --pa -p %t.pa-eret -o %t.out \
+# RUN:   --print-cfg --print-only=main | FileCheck %s --check-prefix=CHECK-ATTACH
+
 ## Check pre-aggregated traces don't report zero-sized PLT fall-through as
 ## invalid trace
 # RUN-DISABLED: llvm-bolt %t.strip --pa -p %t.pa-plt -o %t.out | FileCheck %s \
@@ -92,6 +111,10 @@ Ltmp4_br:
 # PREAGG-RET: T #Lfoo_ret# #Ltmp3# #Ltmp3_br# 1
 ## Target is a secondary entry point (unstripped) or a landing pad (stripped)
 # PREAGG-EXT: T X:0 #Ltmp3# #Ltmp3_br# 1
+## Pre-aggregated return trace
+# PREAGG-PRET: R X:0 #Ltmp3# #Ltmp3_br# 1
+## External return
+# PREAGG-ERET: r #Ltmp3# #Ltmp3_br# 1
 
 # CHECK-ATTACH:      callq foo
 # CHECK-ATTACH-NEXT: count: 1

bolt/test/link_fdata.py

@@ -36,9 +36,9 @@
 fdata_pat = re.compile(r"([01].*) (?P<mispred>\d+) (?P<exec>\d+)")
 
 # Pre-aggregated profile:
-# {T|S|E|B|F|f} <start> [<end>] [<ft_end>] <count> [<mispred_count>]
+# {T|R|S|E|B|F|f|r} <start> [<end>] [<ft_end>] <count> [<mispred_count>]
 # <loc>: [<id>:]<offset>
-preagg_pat = re.compile(r"(?P<type>[TSBFf]) (?P<offsets_count>.*)")
+preagg_pat = re.compile(r"(?P<type>[TRSBFfr]) (?P<offsets_count>.*)")
 
 # No-LBR profile:
 # <is symbol?> <closest elf symbol or DSO name> <relative address> <count>