From 105adf2cd9588b4839fbdc7287bb76a962fdb8ca Mon Sep 17 00:00:00 2001
From: Micah Weston <micahsweston@gmail.com>
Date: Tue, 12 Dec 2023 10:23:16 -0500
Subject: [SHT_LLVM_BB_ADDR_MAP] Implements PGOAnalysisMap in Object and
 ObjectYAML with tests.

Reviewed in PR (#71750). A part of [RFC - PGO Accuracy Metrics: Emitting and Evaluating Branch
and Block
Analysis](https://discourse.llvm.org/t/rfc-pgo-accuracy-metrics-emitting-and-evaluating-branch-and-block-analysis/73902).

This PR adds the PGOAnalysisMap data structure and implements encoding and
decoding through Object and ObjectYAML along with associated tests. When
emitted into the bb-addr-map section, each function is followed by the associated
pgo-analysis-map for that function. The emitting of each analysis in the map is
controlled by a bit in the bb-addr-map feature byte. All existing bb-addr-map
code can ignore the pgo-analysis-map if the caller does not request the data.
---
 llvm/lib/Object/ELFObjectFile.cpp | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

(limited to 'llvm/lib/Object/ELFObjectFile.cpp')

diff --git a/llvm/lib/Object/ELFObjectFile.cpp b/llvm/lib/Object/ELFObjectFile.cpp
index 25dbcbd..3c86b0f 100644
--- a/llvm/lib/Object/ELFObjectFile.cpp
+++ b/llvm/lib/Object/ELFObjectFile.cpp
@@ -716,10 +716,13 @@ std::vector<ELFPltEntry> ELFObjectFileBase::getPltEntries() const {
 
 template <class ELFT>
 Expected<std::vector<BBAddrMap>> static readBBAddrMapImpl(
-    const ELFFile<ELFT> &EF, std::optional<unsigned> TextSectionIndex) {
+    const ELFFile<ELFT> &EF, std::optional<unsigned> TextSectionIndex,
+    std::vector<PGOAnalysisMap> *PGOAnalyses) {
   using Elf_Shdr = typename ELFT::Shdr;
   bool IsRelocatable = EF.getHeader().e_type == ELF::ET_REL;
   std::vector<BBAddrMap> BBAddrMaps;
+  if (PGOAnalyses)
+    PGOAnalyses->clear();
 
   const auto &Sections = cantFail(EF.sections());
   auto IsMatch = [&](const Elf_Shdr &Sec) -> Expected<bool> {
@@ -748,10 +751,13 @@ Expected<std::vector<BBAddrMap>> static readBBAddrMapImpl(
       return createError("unable to get relocation section for " +
                          describe(EF, *Sec));
     Expected<std::vector<BBAddrMap>> BBAddrMapOrErr =
-        EF.decodeBBAddrMap(*Sec, RelocSec);
-    if (!BBAddrMapOrErr)
+        EF.decodeBBAddrMap(*Sec, RelocSec, PGOAnalyses);
+    if (!BBAddrMapOrErr) {
+      if (PGOAnalyses)
+        PGOAnalyses->clear();
       return createError("unable to read " + describe(EF, *Sec) + ": " +
                          toString(BBAddrMapOrErr.takeError()));
+    }
     std::move(BBAddrMapOrErr->begin(), BBAddrMapOrErr->end(),
               std::back_inserter(BBAddrMaps));
   }
@@ -828,13 +834,14 @@ ELFObjectFileBase::readDynsymVersions() const {
 }
 
 Expected<std::vector<BBAddrMap>> ELFObjectFileBase::readBBAddrMap(
-    std::optional<unsigned> TextSectionIndex) const {
+    std::optional<unsigned> TextSectionIndex,
+    std::vector<PGOAnalysisMap> *PGOAnalyses) const {
   if (const auto *Obj = dyn_cast<ELF32LEObjectFile>(this))
-    return readBBAddrMapImpl(Obj->getELFFile(), TextSectionIndex);
+    return readBBAddrMapImpl(Obj->getELFFile(), TextSectionIndex, PGOAnalyses);
   if (const auto *Obj = dyn_cast<ELF64LEObjectFile>(this))
-    return readBBAddrMapImpl(Obj->getELFFile(), TextSectionIndex);
+    return readBBAddrMapImpl(Obj->getELFFile(), TextSectionIndex, PGOAnalyses);
   if (const auto *Obj = dyn_cast<ELF32BEObjectFile>(this))
-    return readBBAddrMapImpl(Obj->getELFFile(), TextSectionIndex);
+    return readBBAddrMapImpl(Obj->getELFFile(), TextSectionIndex, PGOAnalyses);
   return readBBAddrMapImpl(cast<ELF64BEObjectFile>(this)->getELFFile(),
-                           TextSectionIndex);
+                           TextSectionIndex, PGOAnalyses);
 }
-- 
cgit v1.1