[llvm-objcopy] - Simplify `isCompressable` and fix the issue relative.

When --compress-debug-sections is given, llvm-objcopy do not compress
sections that have "ZLIB" header in data. Normally this signature is used
in zlib-gnu compression format. But if zlib-gnu used then the name of the compressed
section should start from .z* (e.g .zdebug_info). If it does not, then it is not
a zlib-gnu format and section should be treated as a normal uncompressed section.

Differential revision: https://reviews.llvm.org/D58908

llvm-svn: 355399

1 files changed, 41 insertions, 0 deletions

diff --git a/llvm/test/tools/llvm-objcopy/ELF/compress-debug-sections-zlib-header.test b/llvm/test/tools/llvm-objcopy/ELF/compress-debug-sections-zlib-header.test
new file mode 100644
index 00000000000..0e7d713aebc
--- /dev/null
+++ b/llvm/test/tools/llvm-objcopy/ELF/compress-debug-sections-zlib-header.test
@@ -0,0 +1,41 @@
+# REQUIRES: zlib
+
+# RUN: yaml2obj %s -o %t1.o
+# RUN: llvm-objcopy --compress-debug-sections %t1.o %t2.o
+# RUN: llvm-readobj -s %t2.o | FileCheck %s
+
+# Non-.zdebug* sections whose data does start with "ZLIB" should
+# not be considered as zlib-gnu compressed sections.
+
+# In this test we have 2 normal sections, one of them starts with "ZLIB",
+# another starts with "ZZZZ". Check we compress both as expected.
+
+# CHECK:        Name: .debug_foo
+# CHECK-NEXT:   Type: SHT_PROGBITS
+# CHECK-NEXT:   Flags [
+# CHECK-NEXT:     SHF_COMPRESSED
+# CHECK-NEXT:   ]
+
+# CHECK:        Name: .debug_bar
+# CHECK-NEXT:   Type: SHT_PROGBITS
+# CHECK-NEXT:   Flags [
+# CHECK-NEXT:     SHF_COMPRESSED
+# CHECK-NEXT:   ]
+
+--- !ELF
+FileHeader:      
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:        
+  - Name:            .debug_foo
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    # "ZLIB"
+    Content:         5A4C49420000000000000000
+  - Name:            .debug_bar
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    # "ZZZZ"
+    Content:         5A5A5A5A0000000000000000