[BOLT] Match functions with name similarity

[shawbyoung]

A mapping - from namespace to associated binary functions - is used to
match function profiles to binary based on the
'--name-similarity-function-matching-threshold' flag set edit distance
threshold. The flag is set to 0 (exact name matching) by default as it is
expensive, requiring the processing of all BFs.

Test Plan: Added name-similarity-function-matching.test. On a binary
with 5M functions, rewrite passes took ~520s without the flag and
~2018s with the flag set to 20.

[llvmbot]

@llvm/pr-subscribers-bolt

Author: shaw young (shawbyoung)

Changes

Matching functions based on edit
distance.

Test Plan: tbd

---

Full diff: https://github.com/llvm/llvm-project/pull/95884.diff

1 Files Affected:

• (modified) bolt/lib/Profile/YAMLProfileReader.cpp (+29)

diff --git a/bolt/lib/Profile/YAMLProfileReader.cpp b/bolt/lib/Profile/YAMLProfileReader.cpp
index f25f59201f1cd..a4f8ba9a440b6 100644
--- a/bolt/lib/Profile/YAMLProfileReader.cpp
+++ b/bolt/lib/Profile/YAMLProfileReader.cpp
@@ -13,6 +13,7 @@
 #include "bolt/Profile/ProfileYAMLMapping.h"
 #include "bolt/Utils/Utils.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/edit_distance.h"
 #include "llvm/Support/CommandLine.h"
 
 using namespace llvm;
@@ -23,6 +24,10 @@ extern cl::opt<unsigned> Verbosity;
 extern cl::OptionCategory BoltOptCategory;
 extern cl::opt<bool> InferStaleProfile;
 
+cl::opt<unsigned> NameSimilarityFunctionMatchingThreshold(
+    "name-similarity-function-matching-threshold", cl::desc("edit distance."),
+    cl::init(0), cl::Hidden, cl::cat(BoltOptCategory));
+
 static llvm::cl::opt<bool>
     IgnoreHash("profile-ignore-hash",
                cl::desc("ignore hash while reading function profile"),
@@ -415,6 +420,30 @@ Error YAMLProfileReader::readProfile(BinaryContext &BC) {
     if (!YamlBF.Used && BF && !ProfiledFunctions.count(BF))
       matchProfileToFunction(YamlBF, *BF);
 
+  // Uses name similarity to match functions that were not matched by name.
+  for (auto YamlBF : YamlBP.Functions) {
+    if (YamlBF.Used)
+      continue;
+
+    unsigned MinEditDistance = UINT_MAX;
+    BinaryFunction *ClosestNameBF = nullptr;
+
+    for (auto &[_, BF] : BC.getBinaryFunctions()) {
+      if (ProfiledFunctions.count(&BF))
+        continue;
+
+      unsigned BFEditDistance = BF.getOneName().edit_distance(YamlBF.Name);
+      if (BFEditDistance < MinEditDistance) {
+        MinEditDistance = BFEditDistance;
+        ClosestNameBF = &BF;
+      }
+    }
+
+    if (ClosestNameBF &&
+      MinEditDistance < opts::NameSimilarityFunctionMatchingThreshold)
+      matchProfileToFunction(YamlBF, *ClosestNameBF);
+  }
+
   for (yaml::bolt::BinaryFunctionProfile &YamlBF : YamlBP.Functions)
     if (!YamlBF.Used && opts::Verbosity >= 1)
       errs() << "BOLT-WARNING: profile ignored for function " << YamlBF.Name

[aaupov]

Can you please also note the runtime of the namespace-filtered pairwise checks? This would guide us in whether to add a BB count filtering.

[shawbyoung]

Can you please also note the runtime of the namespace-filtered pairwise checks? This would guide us in whether to add a BB count filtering.

Ran BOLT on a large binary with 4917369 functions with name similarity function matching - total execution time of rewrite passes was 2235.2883 seconds (1989.1823 wall clock) with an edit distance threshold of 20 and 2194.1708 seconds (1986.2007 wall clock) with an edit distance threshold of 10. Without name similarity matching, total execution time of rewrite passes was 520.4121 seconds (296.4178 wall clock).

[aaupov]

Thank you for checking the runtime, and it's quite high. We'll need extra filtering by block count to keep runtime low - please add it as we discussed.

[shawbyoung]

Thank you for checking the runtime, and it's quite high. We'll need extra filtering by block count to keep runtime low - please add it as we discussed.

if (BF->size() != YamlBF.NumBasicBlocks)
continue;

Functions are filtered by block size here @aaupov

[maksfb]

Please refactor new code into a separate function. Add a comment on how the matching is done such that the interface can be understood without reading the code.

[aaupov]

LG in general with some comments

[aaupov]

LG with a couple of nits.

[llvm-ci]

LLVM Buildbot has detected a new failure on builder bolt-x86_64-ubuntu-shared running on bolt-worker while building bolt at step 5 "build-bolt".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/151/builds/775

Here is the relevant piece of the build log for the reference:

Step 5 (build-bolt) failure: build (failure)
0.010 [90/2/1] Performing build step for 'bolt_rt'
ninja: no work to do.
0.013 [89/2/2] Generating VCSRevision.h
0.020 [7/4/3] No install step for 'bolt_rt'
0.035 [6/4/4] Completed 'bolt_rt'
6.100 [6/3/5] Building CXX object tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/StaleProfileMatching.cpp.o
6.692 [6/2/6] Building CXX object tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/YAMLProfileReader.cpp.o
6.728 [5/2/7] Linking CXX shared library lib/libLLVMBOLTProfile.so.19.0git
FAILED: lib/libLLVMBOLTProfile.so.19.0git 
: && /usr/bin/c++ -fPIC -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -fno-lifetime-dse -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-uninitialized -Wno-nonnull -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG  -Wl,-z,defs -Wl,-z,nodelete -fuse-ld=lld -Wl,--color-diagnostics   -Wl,--gc-sections -shared -Wl,-soname,libLLVMBOLTProfile.so.19.0git -o lib/libLLVMBOLTProfile.so.19.0git tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/BoltAddressTranslation.cpp.o tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/DataAggregator.cpp.o tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/DataReader.cpp.o tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/Heatmap.cpp.o tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/StaleProfileMatching.cpp.o tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/YAMLProfileReader.cpp.o tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/YAMLProfileWriter.cpp.o  -Wl,-rpath,"\$ORIGIN/../lib:/home/worker/bolt-worker2/bolt-x86_64-ubuntu-shared/build/lib:"  lib/libLLVMBOLTCore.so.19.0git  lib/libLLVMBOLTUtils.so.19.0git  lib/libLLVMTransformUtils.so.19.0git  lib/libLLVMSupport.so.19.0git  -Wl,-rpath-link,/home/worker/bolt-worker2/bolt-x86_64-ubuntu-shared/build/lib && :
ld.lld: error: undefined symbol: llvm::ItaniumPartialDemangler::ItaniumPartialDemangler()
>>> referenced by YAMLProfileReader.cpp
>>>               tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/YAMLProfileReader.cpp.o:(llvm::bolt::YAMLProfileReader::matchWithNameSimilarity(llvm::bolt::BinaryContext&) (.localalias))

ld.lld: error: undefined symbol: llvm::demangle[abi:cxx11](std::basic_string_view<char, std::char_traits<char>>)
>>> referenced by YAMLProfileReader.cpp
>>>               tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/YAMLProfileReader.cpp.o:(llvm::bolt::YAMLProfileReader::matchWithNameSimilarity(llvm::bolt::BinaryContext&) (.localalias))

ld.lld: error: undefined symbol: llvm::ItaniumPartialDemangler::partialDemangle(char const*)
>>> referenced by YAMLProfileReader.cpp
>>>               tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/YAMLProfileReader.cpp.o:(llvm::bolt::YAMLProfileReader::matchWithNameSimilarity(llvm::bolt::BinaryContext&) (.localalias))
>>> referenced by YAMLProfileReader.cpp
>>>               tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/YAMLProfileReader.cpp.o:(llvm::bolt::YAMLProfileReader::matchWithNameSimilarity(llvm::bolt::BinaryContext&) (.localalias))

ld.lld: error: undefined symbol: llvm::ItaniumPartialDemangler::getFunctionDeclContextName(char*, unsigned long*) const
>>> referenced by YAMLProfileReader.cpp
>>>               tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/YAMLProfileReader.cpp.o:(llvm::bolt::YAMLProfileReader::matchWithNameSimilarity(llvm::bolt::BinaryContext&) (.localalias))
>>> referenced by YAMLProfileReader.cpp
>>>               tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/YAMLProfileReader.cpp.o:(llvm::bolt::YAMLProfileReader::matchWithNameSimilarity(llvm::bolt::BinaryContext&) (.localalias))

ld.lld: error: undefined symbol: llvm::ItaniumPartialDemangler::~ItaniumPartialDemangler()
>>> referenced by YAMLProfileReader.cpp
>>>               tools/bolt/lib/Profile/CMakeFiles/LLVMBOLTProfile.dir/YAMLProfileReader.cpp.o:(llvm::bolt::YAMLProfileReader::matchWithNameSimilarity(llvm::bolt::BinaryContext&) (.localalias))
collect2: error: ld returned 1 exit status
19.233 [5/1/8] Building CXX object tools/bolt/lib/Rewrite/CMakeFiles/LLVMBOLTRewrite.dir/RewriteInstance.cpp.o
ninja: build stopped: subcommand failed.