[LLD][ELF] Fix compressed-debug-level test on SystemZ

[uweigand]

Summary

The libz compression library on SystemZ by default makes use of the platform's hardware-accelerated compression facility. This is much faster than the regular software implementation, but often results in slightly different outputs. This causes failures with the compressed-debug-level test case.

To fix this, run this test while setting the DFLTCC environment variable to zero, which prevents use of hardware compression and falls back to the software implementation. (This should not have any effect on other platforms.)

[mysterymath]

Hey, looks like this is causing test failures on the Fuchsia Windows builders:
https://luci-milo.appspot.com/ui/p/fuchsia/builders/toolchain.ci/clang-windows-x64/b8782647969396934929/overview

Script:
--
: 'RUN: at line 3';   c:\b\s\w\ir\x\w\staging\llvm_build\bin\yaml2obj.exe C:\b\s\w\ir\x\w\llvm-llvm-project\lld\test\ELF\compressed-debug-level.test -o C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.o
: 'RUN: at line 9';   DFLTCC=0 c:\b\s\w\ir\x\w\staging\llvm_build\bin\ld.lld.exe C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.o -o C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.default --compress-debug-sections=zlib
: 'RUN: at line 10';   c:\b\s\w\ir\x\w\staging\llvm_build\bin\llvm-readelf.exe --sections C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.default | c:\b\s\w\ir\x\w\staging\llvm_build\bin\filecheck.exe -check-prefixes=HEADER,LEVEL1 C:\b\s\w\ir\x\w\llvm-llvm-project\lld\test\ELF\compressed-debug-level.test
: 'RUN: at line 12';   DFLTCC=0 c:\b\s\w\ir\x\w\staging\llvm_build\bin\ld.lld.exe -O0 C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.o -o C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.O0 --compress-debug-sections=zlib
: 'RUN: at line 13';   c:\b\s\w\ir\x\w\staging\llvm_build\bin\llvm-readelf.exe --sections C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.O0 | c:\b\s\w\ir\x\w\staging\llvm_build\bin\filecheck.exe -check-prefixes=HEADER,LEVEL1 C:\b\s\w\ir\x\w\llvm-llvm-project\lld\test\ELF\compressed-debug-level.test
: 'RUN: at line 14';   cmp C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.default C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.O0
: 'RUN: at line 16';   DFLTCC=0 c:\b\s\w\ir\x\w\staging\llvm_build\bin\ld.lld.exe -O1 C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.o -o C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.O1 --compress-debug-sections=zlib
: 'RUN: at line 17';   c:\b\s\w\ir\x\w\staging\llvm_build\bin\llvm-readelf.exe --sections C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.O1 | c:\b\s\w\ir\x\w\staging\llvm_build\bin\filecheck.exe -check-prefixes=HEADER,LEVEL1 C:\b\s\w\ir\x\w\llvm-llvm-project\lld\test\ELF\compressed-debug-level.test
: 'RUN: at line 18';   cmp C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.default C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.O1
: 'RUN: at line 20';   DFLTCC=0 c:\b\s\w\ir\x\w\staging\llvm_build\bin\ld.lld.exe -O2 C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.o -o C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.O2 --compress-debug-sections=zlib
: 'RUN: at line 21';   c:\b\s\w\ir\x\w\staging\llvm_build\bin\llvm-readelf.exe --sections C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.O2 | c:\b\s\w\ir\x\w\staging\llvm_build\bin\filecheck.exe -check-prefixes=HEADER,LEVEL6 C:\b\s\w\ir\x\w\llvm-llvm-project\lld\test\ELF\compressed-debug-level.test
--
Exit Code: 127

Command Output (stdout):
--
$ ":" "RUN: at line 3"
$ "c:\b\s\w\ir\x\w\staging\llvm_build\bin\yaml2obj.exe" "C:\b\s\w\ir\x\w\llvm-llvm-project\lld\test\ELF\compressed-debug-level.test" "-o" "C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.o"
$ ":" "RUN: at line 9"
$ "DFLTCC=0" "c:\b\s\w\ir\x\w\staging\llvm_build\bin\ld.lld.exe" "C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.o" "-o" "C:\b\s\w\ir\x\w\staging\llvm_build\tools\lld\test\ELF\Output\compressed-debug-level.test.tmp.default" "--compress-debug-sections=zlib"
# command stderr:
'DFLTCC=0': command not found
error: command failed with exit status: 127

--

[uweigand]

I've reverted this now as 84539a24632235868cb58f3c167838e32fa42940. Sorry for the breakage. I'll look for another way to set env variables that also works on Windows, and resubmit.

[uweigand]

Use config.environment to set environment variable.

[uweigand]

This version now uses config.environment to set the DFLTCC environment variable, which should work on any supported platform. In addition, the environment variable is only set on SystemZ as host platform.

[MaskRay]

LGTM.

lld/test/ELF/compressed-debug-level.test

 # REQUIRES: x86, zlib
 
 # RUN: yaml2obj %s -o %t.o
 
-# RUN: ld.lld %t.o -o %t.default --compress-debug-sections=zlib
+## The environment variable DFLTCC=0 disables use of the hardware compression
+## facility on SystemZ.  When this facility is enabled, slightly different
+## compression results can be seen, which would throw off the tests below.
+
+# RUN: DFLTCC=0 ld.lld %t.o -o %t.default --compress-debug-sections=zlib
 # RUN: llvm-readelf --sections %t.default | FileCheck -check-prefixes=HEADER,LEVEL1 %s
 
-# RUN: ld.lld -O0 %t.o -o %t.O0 --compress-debug-sections=zlib
+# RUN: DFLTCC=0 ld.lld -O0 %t.o -o %t.O0 --compress-debug-sections=zlib
 # RUN: llvm-readelf --sections %t.O0 | FileCheck -check-prefixes=HEADER,LEVEL1 %s
 # RUN: cmp %t.default %t.O0
 
-# RUN: ld.lld -O1 %t.o -o %t.O1 --compress-debug-sections=zlib
+# RUN: DFLTCC=0 ld.lld -O1 %t.o -o %t.O1 --compress-debug-sections=zlib
 # RUN: llvm-readelf --sections %t.O1 | FileCheck -check-prefixes=HEADER,LEVEL1 %s
 # RUN: cmp %t.default %t.O1
 
-# RUN: ld.lld -O2 %t.o -o %t.O2 --compress-debug-sections=zlib
+# RUN: DFLTCC=0 ld.lld -O2 %t.o -o %t.O2 --compress-debug-sections=zlib
 # RUN: llvm-readelf --sections %t.O2 | FileCheck -check-prefixes=HEADER,LEVEL6 %s
 
 ## LLD uses zlib compression of level 1 when -O0, -O1 and level 6 when -O2.
 ## Here we check how -O flag affects the size of compressed sections produced.
 
 # HEADER: [Nr] Name        Type     Address  Off    Size
 # LEVEL1: [ 1] .debug_info PROGBITS 00000000 000094 00001{{[bc]}}
 # LEVEL6: [ 1] .debug_info PROGBITS 00000000 000094 00001a