[SHT_LLVM_BB_ADDR_MAP] Support decompressing the SHT_LLVM_BB_ADDR_MAP section. #142825
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@llvm/pr-subscribers-llvm-binary-utilities Author: Rahman Lavaee (rlavaee) ChangesCompression of SHT_LLVM_BB_ADDR_MAP with zstd can give 3X compression ratio, which is especially beneficial with PGO_analysis_map. To read the data back, we must decompress it. Though we can use llvm-objcopy to do this, it's much better to do this decompression internally in the library API. Full diff: https://github.com/llvm/llvm-project/pull/142825.diff 2 Files Affected:
diff --git a/llvm/lib/Object/ELF.cpp b/llvm/lib/Object/ELF.cpp
index dfc8acb0e4542..bd9e0b6d24226 100644
--- a/llvm/lib/Object/ELF.cpp
+++ b/llvm/lib/Object/ELF.cpp
@@ -9,6 +9,7 @@
#include "llvm/Object/ELF.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/Object/Decompressor.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/DataExtractor.h"
@@ -782,6 +783,26 @@ decodeBBAddrMapImpl(const ELFFile<ELFT> &EF,
if (!ContentsOrErr)
return ContentsOrErr.takeError();
ArrayRef<uint8_t> Content = *ContentsOrErr;
+
+ // Decompress the section if needed.
+ std::unique_ptr<uint8_t[]> DecompressedContent;
+ if (Sec.sh_flags & llvm::ELF::SHF_COMPRESSED) {
+ Expected<StringRef> SectionNameOrErr = EF.getSectionName(Sec);
+ if (!SectionNameOrErr)
+ return SectionNameOrErr.takeError();
+ auto DecompressorOrErr =
+ Decompressor::create(*SectionNameOrErr, toStringRef(*ContentsOrErr),
+ EF.isLE(), ELFT::Is64Bits);
+ if (!DecompressorOrErr)
+ return DecompressorOrErr.takeError();
+ size_t DecompressedSize = DecompressorOrErr->getDecompressedSize();
+ DecompressedContent = std::make_unique<uint8_t[]>(DecompressedSize);
+ if (Error Err = DecompressorOrErr->decompress(
+ {DecompressedContent.get(), size_t(DecompressedSize)}))
+ return std::move(Err);
+ Content = {DecompressedContent.get(), DecompressedSize};
+ }
+
DataExtractor Data(Content, EF.isLE(), ELFT::Is64Bits ? 8 : 4);
std::vector<BBAddrMap> FunctionEntries;
diff --git a/llvm/test/tools/llvm-readobj/ELF/bb-addr-map.test b/llvm/test/tools/llvm-readobj/ELF/bb-addr-map.test
index c5d071c11d1de..7e584694e07f2 100644
--- a/llvm/test/tools/llvm-readobj/ELF/bb-addr-map.test
+++ b/llvm/test/tools/llvm-readobj/ELF/bb-addr-map.test
@@ -5,15 +5,19 @@
# RUN: llvm-readobj %t1.x64.o --bb-addr-map 2>&1 | FileCheck %s -DADDR=0x999999999 -DFILE=%t1.x64.o --check-prefix=CHECK
# RUN: llvm-readelf %t1.x64.o --bb-addr-map | FileCheck %s --check-prefix=GNU
-## Check 64-bit:
-# RUN: yaml2obj --docnum=1 %s -DBITS=64 -DADDR=0x999999999 -o %t1.v1.x64.o
-# RUN: llvm-readobj %t1.v1.x64.o --bb-addr-map 2>&1 | FileCheck %s -DADDR=0x999999999 -DFILE=%t1.v1.x64.o --check-prefix=CHECK
+## Check compressed sections:
+# RUN: llvm-objcopy %t1.x64.o --compress-sections .llvm_bb_addr_map=zstd %t1.x64.compressed.o
+# RUN: llvm-readobj %t1.x64.compressed.o --bb-addr-map 2>&1 | FileCheck %s -DADDR=0x999999999 -DFILE=%t1.x64.compressed.o --check-prefix=CHECK
## Check 32-bit:
# RUN: yaml2obj --docnum=1 %s -DBITS=32 -o %t1.x32.o
# RUN: llvm-readobj %t1.x32.o --bb-addr-map 2>&1 | FileCheck -DADDR=0x11111 %s -DFILE=%t1.x32.o --check-prefix=CHECK
# RUN: llvm-readelf %t1.x32.o --bb-addr-map | FileCheck %s --check-prefix=GNU
+## Check compressed sections:
+# RUN: llvm-objcopy %t1.x32.o --compress-sections .llvm_bb_addr_map=zstd %t1.x32.compressed.o
+# RUN: llvm-readobj %t1.x32.compressed.o --bb-addr-map 2>&1 | FileCheck %s -DADDR=0x11111 -DFILE=%t1.x32.compressed.o --check-prefix=CHECK
+
## Check that a malformed section can be handled.
# RUN: yaml2obj --docnum=1 %s -DBITS=32 -DSIZE=7 -o %t2.o
# RUN: llvm-readobj %t2.o --bb-addr-map 2>&1 | FileCheck %s -DOFFSET=0x00000007 -DFILE=%t2.o --check-prefix=TRUNCATED
|
Thanks. Moved to the new test tagged with
Yes. It's as simple as |
rlavaee
changed the title
boomanaiden154
approved these changes
Jun 4, 2025
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/186/builds/9629 Here is the relevant piece of the build log for the reference |
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Compression of SHT_LLVM_BB_ADDR_MAP with zstd can give 3X compression ratio, which is especially beneficial with PGO_analysis_map. To read the data back, we must decompress it. Though we can use llvm-objcopy to do this, it's much better to do this decompression internally in the library API.