[BOLT] Support pre-aggregated returns #143296
Open
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Created using spr 1.3.4
Created using spr 1.3.4
aaupov
requested review from
maksfb,
rafaelauler,
ayermolo,
yota9 and
paschalis-mpeis
as code owners
|
@llvm/pr-subscribers-bolt Author: Amir Ayupov (aaupov) ChangesIntel's Architectural LBR supports capturing branch type information Linux kernel can preserve branch type when > - save_type: save branch type during sampling in case binary is not available later. This information is needed to disambiguate external returns (from This patch adds new pre-aggregated trace type (R). Test Plan: updated callcont-fallthru.s Full diff: https://github.com/llvm/llvm-project/pull/143296.diff 4 Files Affected:
diff --git a/bolt/include/bolt/Profile/DataAggregator.h b/bolt/include/bolt/Profile/DataAggregator.h
index 96969cf53baca..ae66c58e127cd 100644
--- a/bolt/include/bolt/Profile/DataAggregator.h
+++ b/bolt/include/bolt/Profile/DataAggregator.h
@@ -109,6 +109,7 @@ class DataAggregator : public DataReader {
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 BR_EXTERNAL_RETURN = -3ULL;
uint64_t Branch;
uint64_t From;
@@ -388,7 +389,7 @@ 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>
///
@@ -403,6 +404,7 @@ class DataAggregator : public DataReader {
/// jump to the block
/// 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
@@ -532,6 +534,9 @@ inline raw_ostream &operator<<(raw_ostream &OS,
case DataAggregator::Trace::FT_ONLY:
case DataAggregator::Trace::FT_EXTERNAL_ORIGIN:
break;
+ case DataAggregator::Trace::BR_EXTERNAL_RETURN:
+ OS << "0 -> ";
+ break;
default:
OS << Twine::utohexstr(T.Branch) << " -> ";
}
diff --git a/bolt/lib/Profile/DataAggregator.cpp b/bolt/lib/Profile/DataAggregator.cpp
index 11d282e98413b..c28dd6e57f8e4 100644
--- a/bolt/lib/Profile/DataAggregator.cpp
+++ b/bolt/lib/Profile/DataAggregator.cpp
@@ -1194,6 +1194,7 @@ std::error_code DataAggregator::parseAggregatedLBREntry() {
INVALID = 0,
EVENT_NAME, // E
TRACE, // T
+ RETURN, // R
SAMPLE, // S
BRANCH, // B
FT, // F
@@ -1224,6 +1225,7 @@ 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)
@@ -1237,7 +1239,7 @@ std::error_code DataAggregator::parseAggregatedLBREntry() {
}
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);
}
@@ -1295,8 +1297,13 @@ std::error_code DataAggregator::parseAggregatedLBREntry() {
Addr[0] = Location(Type == FT ? Trace::FT_ONLY : Trace::FT_EXTERNAL_ORIGIN);
}
- if (Type == BRANCH) {
+ if (Type == BRANCH)
Addr[2] = Location(Trace::BR_ONLY);
+
+ if (Type == RETURN) {
+ if (!Addr[0]->Offset)
+ Addr[0]->Offset = Trace::BR_EXTERNAL_RETURN;
+ Returns.emplace(Addr[0]->Offset);
}
Trace T{Addr[0]->Offset, Addr[1]->Offset, Addr[2]->Offset};
diff --git a/bolt/test/X86/callcont-fallthru.s b/bolt/test/X86/callcont-fallthru.s
index c2ef024db9475..63142903c80d2 100644
--- a/bolt/test/X86/callcont-fallthru.s
+++ b/bolt/test/X86/callcont-fallthru.s
@@ -10,6 +10,8 @@
# 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
# RUN-DISABLED: link_fdata %s %t %t.pa-plt PREAGG-PLT
# RUN: llvm-strip --strip-unneeded %t -o %t.strip
@@ -38,6 +40,15 @@
# 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
+
## 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 +103,8 @@ 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
# CHECK-ATTACH: callq foo
# CHECK-ATTACH-NEXT: count: 1
diff --git a/bolt/test/link_fdata.py b/bolt/test/link_fdata.py
index 5a9752068bb9f..cb6b3c7baaab5 100755
--- a/bolt/test/link_fdata.py
+++ b/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} <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>[TRSBFf]) (?P<offsets_count>.*)")
# No-LBR profile:
# <is symbol?> <closest elf symbol or DSO name> <relative address> <count>
|
# for free
to join this conversation on GitHub.
Already have an account?
# to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Intel's Architectural LBR supports capturing branch type information
as part of LBR stack (SDM Vol 3B, part 2, October 2024):
Linux kernel can preserve branch type when
save_typeis enabled,even if CPU does not support Architectural LBR:
https://github.com/torvalds/linux/blob/f09079bd04a924c72d555cd97942d5f8d7eca98c/tools/perf/Documentation/perf-record.txt#L457-L460
This information is needed to disambiguate external returns (from
DSO/JIT) to an entry point or a landing pad, when BOLT can't
disassemble the branch source.
This patch adds new pre-aggregated trace type (R).
Depends on #143295.
Test Plan: updated callcont-fallthru.s