[ThinLTO] Compute the basic block count across modules.

Summary:
Count the per-module number of basic blocks when the module summary is computed
and sum them up during Thin LTO indexing.

This is used to estimate the working set size under the partial sample PGO.

This is split off of D79831.

Reviewers: davidxl, espindola

Subscribers: emaste, inglorion, hiraditya, MaskRay, steven_wu, dexonsmith, arphaman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D80403

3 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Bitcode/Reader/BitcodeAnalyzer.cpp b/llvm/lib/Bitcode/Reader/BitcodeAnalyzer.cpp
index 69ab822..a72a33a 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeAnalyzer.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeAnalyzer.cpp
@@ -305,6 +305,7 @@ static Optional<const char *> GetCodeName(unsigned CodeID, unsigned BlockID,
       STRINGIFY_CODE(FS, CFI_FUNCTION_DECLS)
       STRINGIFY_CODE(FS, TYPE_ID)
       STRINGIFY_CODE(FS, TYPE_ID_METADATA)
+      STRINGIFY_CODE(FS, BLOCK_COUNT)
     }
   case bitc::METADATA_ATTACHMENT_ID:
     switch (CodeID) {
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 4bad2b5..615b646 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -6239,6 +6239,9 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(unsigned ID) {
     case bitc::FS_TYPE_ID_METADATA:
       parseTypeIdCompatibleVtableSummaryRecord(Record);
       break;
+
+    case bitc::FS_BLOCK_COUNT:
+      TheIndex.addBlockCount(Record[0]);
     }
   }
   llvm_unreachable("Exit infinite loop");
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index a46339a..992cdfc 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -3906,6 +3906,9 @@ void ModuleBitcodeWriterBase::writePerModuleGlobalValueSummary() {
     NameVals.clear();
   }
 
+  Stream.EmitRecord(bitc::FS_BLOCK_COUNT,
+                    ArrayRef<uint64_t>{Index->getBlockCount()});
+
   Stream.ExitBlock();
 }
 
@@ -4189,6 +4192,9 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
     }
   }
 
+  Stream.EmitRecord(bitc::FS_BLOCK_COUNT,
+                    ArrayRef<uint64_t>{Index.getBlockCount()});
+
   Stream.ExitBlock();
 }