gcc49 @4.9.3: does not honor -march=native

[noloader (Jeffrey Walton)]

I'm attempting a compile uder MacPort's GCC compiler:

$ make CXX=/opt/local//bin/x86_64-apple-darwin12-gcc-4.9.3
/opt/local//bin/x86_64-apple-darwin12-gcc-4.9.3 -DNDEBUG -g2 -O2 -fPIC -march=native -pipe -c cryptlib.cpp
:1057:no such instruction: `vzeroupper'
:1507:no such instruction: `vzeroupper'
:1517:no such instruction: `vzeroupper'
:1662:no such instruction: `vzeroupper'
:1838:no such instruction: `vzeroupper'
...

Piping it into wc reveals:

$ make CXX=/opt/local//bin/x86_64-apple-darwin12-gcc-4.9.3 2>&1 | wc -l
     190

The machine is a 2012 MacBook Pro with a Core i7-2760QM. Broadly speaking, the cpu includes SSE4 and AES-NI, but lacks RDRAND and RDSEED:

$ sysctl -a | grep machdep.cpu.features
machdep.cpu.features: FPU VME DE PSE TSC MSR PAE MCE CX8 APIC SEP MTRR PGE MCA CMOV PAT PSE36 CLFSH DS ACPI MMX FXSR SSE SSE2 SS HTT TM PBE SSE3 PCLMULQDQ DTES64 MON DSCPL VMX SMX EST TM2 SSSE3 CX16 TPR PDCM SSE4.1 SSE4.2 x2APIC POPCNT AES PCID XSAVE OSXSAVE TSCTMR AVX1.0

vzeroupper is part of AVX, and AVX is available in the cpu feature set.

We have users who use a few MacPorts compilers, so I'm guessing additional testing will reveal the same issue under GCC 5.1 and 5.3. I'm only going to file this one report, however.

---

Here's some additional information that may be useful.

$  port version
Version: 2.3.4

And:

$ sysctl -a | grep machdep.cpu
machdep.cpu.max_basic: 13
machdep.cpu.max_ext: 2147483656
machdep.cpu.vendor: GenuineIntel
machdep.cpu.brand_string: Intel(R) Core(TM) i7-2760QM CPU @ 2.40GHz
machdep.cpu.family: 6
machdep.cpu.model: 42
machdep.cpu.extmodel: 2
machdep.cpu.extfamily: 0
machdep.cpu.stepping: 7
machdep.cpu.feature_bits: 3219913727 532341759
machdep.cpu.extfeature_bits: 672139520 1
machdep.cpu.signature: 132775
machdep.cpu.brand: 0
machdep.cpu.features: FPU VME DE PSE TSC MSR PAE MCE CX8 APIC SEP MTRR PGE MCA CMOV PAT PSE36 CLFSH DS ACPI MMX FXSR SSE SSE2 SS HTT TM PBE SSE3 PCLMULQDQ DTES64 MON DSCPL VMX SMX EST TM2 SSSE3 CX16 TPR PDCM SSE4.1 SSE4.2 x2APIC POPCNT AES PCID XSAVE OSXSAVE TSCTMR AVX1.0
machdep.cpu.extfeatures: SYSCALL XD EM64T LAHF RDTSCP TSCI
machdep.cpu.logical_per_package: 16
machdep.cpu.cores_per_package: 8
machdep.cpu.microcode_version: 26
machdep.cpu.processor_flag: 4
machdep.cpu.mwait.linesize_min: 64
machdep.cpu.mwait.linesize_max: 64
machdep.cpu.mwait.extensions: 3
machdep.cpu.mwait.sub_Cstates: 135456
machdep.cpu.thermal.sensor: 1
machdep.cpu.thermal.dynamic_acceleration: 1
machdep.cpu.thermal.invariant_APIC_timer: 1
machdep.cpu.thermal.thresholds: 2
machdep.cpu.thermal.ACNT_MCNT: 1
machdep.cpu.thermal.core_power_limits: 1
machdep.cpu.thermal.fine_grain_clock_mod: 1
machdep.cpu.thermal.package_thermal_intr: 1
machdep.cpu.thermal.hardware_feedback: 0
machdep.cpu.thermal.energy_policy: 0
machdep.cpu.xsave.extended_state: 7 832 832 0
machdep.cpu.arch_perf.version: 3
machdep.cpu.arch_perf.number: 4
machdep.cpu.arch_perf.width: 48
machdep.cpu.arch_perf.events_number: 7
machdep.cpu.arch_perf.events: 0
machdep.cpu.arch_perf.fixed_number: 3
machdep.cpu.arch_perf.fixed_width: 48
machdep.cpu.cache.linesize: 64
machdep.cpu.cache.L2_associativity: 8
machdep.cpu.cache.size: 256
machdep.cpu.tlb.inst.small: 64
machdep.cpu.tlb.inst.large: 8
machdep.cpu.tlb.data.small: 64
machdep.cpu.tlb.data.large: 32
machdep.cpu.tlb.shared: 512
machdep.cpu.address_bits.physical: 36
machdep.cpu.address_bits.virtual: 48
machdep.cpu.core_count: 4
machdep.cpu.thread_count: 8

[noloader (Jeffrey Walton)]

I probably should have supplied this with the original report. Sorry about that.

$ /opt/local//bin/x86_64-apple-darwin12-gcc-4.9.3 -march=native -dM -E - < /dev/null | sort
#define _LP64 1
#define __AES__ 1
#define __APPLE_CC__ 1
#define __APPLE__ 1
#define __ATOMIC_ACQUIRE 2
#define __ATOMIC_ACQ_REL 4
#define __ATOMIC_CONSUME 1
#define __ATOMIC_HLE_ACQUIRE 65536
#define __ATOMIC_HLE_RELEASE 131072
#define __ATOMIC_RELAXED 0
#define __ATOMIC_RELEASE 3
#define __ATOMIC_SEQ_CST 5
#define __AVX__ 1
#define __BIGGEST_ALIGNMENT__ 32
#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
#define __CHAR16_TYPE__ short unsigned int
#define __CHAR32_TYPE__ unsigned int
#define __CHAR_BIT__ 8
#define __CONSTANT_CFSTRINGS__ 1
#define __DBL_DECIMAL_DIG__ 17
#define __DBL_DENORM_MIN__ ((double)4.94065645841246544177e-324L)
#define __DBL_DIG__ 15
#define __DBL_EPSILON__ ((double)2.22044604925031308085e-16L)
#define __DBL_HAS_DENORM__ 1
#define __DBL_HAS_INFINITY__ 1
#define __DBL_HAS_QUIET_NAN__ 1
#define __DBL_MANT_DIG__ 53
#define __DBL_MAX_10_EXP__ 308
#define __DBL_MAX_EXP__ 1024
#define __DBL_MAX__ ((double)1.79769313486231570815e+308L)
#define __DBL_MIN_10_EXP__ (-307)
#define __DBL_MIN_EXP__ (-1021)
#define __DBL_MIN__ ((double)2.22507385850720138309e-308L)
#define __DEC128_EPSILON__ 1E-33DL
#define __DEC128_MANT_DIG__ 34
#define __DEC128_MAX_EXP__ 6145
#define __DEC128_MAX__ 9.999999999999999999999999999999999E6144DL
#define __DEC128_MIN_EXP__ (-6142)
#define __DEC128_MIN__ 1E-6143DL
#define __DEC128_SUBNORMAL_MIN__ 0.000000000000000000000000000000001E-6143DL
#define __DEC32_EPSILON__ 1E-6DF
#define __DEC32_MANT_DIG__ 7
#define __DEC32_MAX_EXP__ 97
#define __DEC32_MAX__ 9.999999E96DF
#define __DEC32_MIN_EXP__ (-94)
#define __DEC32_MIN__ 1E-95DF
#define __DEC32_SUBNORMAL_MIN__ 0.000001E-95DF
#define __DEC64_EPSILON__ 1E-15DD
#define __DEC64_MANT_DIG__ 16
#define __DEC64_MAX_EXP__ 385
#define __DEC64_MAX__ 9.999999999999999E384DD
#define __DEC64_MIN_EXP__ (-382)
#define __DEC64_MIN__ 1E-383DD
#define __DEC64_SUBNORMAL_MIN__ 0.000000000000001E-383DD
#define __DECIMAL_DIG__ 21
#define __DEC_EVAL_METHOD__ 2
#define __DYNAMIC__ 1
#define __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ 1086
#define __FINITE_MATH_ONLY__ 0
#define __FLOAT_WORD_ORDER__ __ORDER_LITTLE_ENDIAN__
#define __FLT_DECIMAL_DIG__ 9
#define __FLT_DENORM_MIN__ 1.40129846432481707092e-45F
#define __FLT_DIG__ 6
#define __FLT_EPSILON__ 1.19209289550781250000e-7F
#define __FLT_EVAL_METHOD__ 0
#define __FLT_HAS_DENORM__ 1
#define __FLT_HAS_INFINITY__ 1
#define __FLT_HAS_QUIET_NAN__ 1
#define __FLT_MANT_DIG__ 24
#define __FLT_MAX_10_EXP__ 38
#define __FLT_MAX_EXP__ 128
#define __FLT_MAX__ 3.40282346638528859812e+38F
#define __FLT_MIN_10_EXP__ (-37)
#define __FLT_MIN_EXP__ (-125)
#define __FLT_MIN__ 1.17549435082228750797e-38F
#define __FLT_RADIX__ 2
#define __FXSR__ 1
#define __GCC_ATOMIC_BOOL_LOCK_FREE 2
#define __GCC_ATOMIC_CHAR16_T_LOCK_FREE 2
#define __GCC_ATOMIC_CHAR32_T_LOCK_FREE 2
#define __GCC_ATOMIC_CHAR_LOCK_FREE 2
#define __GCC_ATOMIC_INT_LOCK_FREE 2
#define __GCC_ATOMIC_LLONG_LOCK_FREE 2
#define __GCC_ATOMIC_LONG_LOCK_FREE 2
#define __GCC_ATOMIC_POINTER_LOCK_FREE 2
#define __GCC_ATOMIC_SHORT_LOCK_FREE 2
#define __GCC_ATOMIC_TEST_AND_SET_TRUEVAL 1
#define __GCC_ATOMIC_WCHAR_T_LOCK_FREE 2
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 1
#define __GCC_IEC_559 2
#define __GCC_IEC_559_COMPLEX 2
#define __GNUC_GNU_INLINE__ 1
#define __GNUC_MINOR__ 9
#define __GNUC_PATCHLEVEL__ 3
#define __GNUC__ 4
#define __GXX_ABI_VERSION 1002
#define __INT16_C(c) c
#define __INT16_MAX__ 32767
#define __INT16_TYPE__ short int
#define __INT32_C(c) c
#define __INT32_MAX__ 2147483647
#define __INT32_TYPE__ int
#define __INT64_C(c) c ## LL
#define __INT64_MAX__ 9223372036854775807LL
#define __INT64_TYPE__ long long int
#define __INT8_C(c) c
#define __INT8_MAX__ 127
#define __INT8_TYPE__ signed char
#define __INTMAX_C(c) c ## L
#define __INTMAX_MAX__ 9223372036854775807L
#define __INTMAX_TYPE__ long int
#define __INTPTR_MAX__ 9223372036854775807L
#define __INTPTR_TYPE__ long int
#define __INT_FAST16_MAX__ 32767
#define __INT_FAST16_TYPE__ short int
#define __INT_FAST32_MAX__ 2147483647
#define __INT_FAST32_TYPE__ int
#define __INT_FAST64_MAX__ 9223372036854775807LL
#define __INT_FAST64_TYPE__ long long int
#define __INT_FAST8_MAX__ 127
#define __INT_FAST8_TYPE__ signed char
#define __INT_LEAST16_MAX__ 32767
#define __INT_LEAST16_TYPE__ short int
#define __INT_LEAST32_MAX__ 2147483647
#define __INT_LEAST32_TYPE__ int
#define __INT_LEAST64_MAX__ 9223372036854775807LL
#define __INT_LEAST64_TYPE__ long long int
#define __INT_LEAST8_MAX__ 127
#define __INT_LEAST8_TYPE__ signed char
#define __INT_MAX__ 2147483647
#define __LDBL_DENORM_MIN__ 3.64519953188247460253e-4951L
#define __LDBL_DIG__ 18
#define __LDBL_EPSILON__ 1.08420217248550443401e-19L
#define __LDBL_HAS_DENORM__ 1
#define __LDBL_HAS_INFINITY__ 1
#define __LDBL_HAS_QUIET_NAN__ 1
#define __LDBL_MANT_DIG__ 64
#define __LDBL_MAX_10_EXP__ 4932
#define __LDBL_MAX_EXP__ 16384
#define __LDBL_MAX__ 1.18973149535723176502e+4932L
#define __LDBL_MIN_10_EXP__ (-4931)
#define __LDBL_MIN_EXP__ (-16381)
#define __LDBL_MIN__ 3.36210314311209350626e-4932L
#define __LITTLE_ENDIAN__ 1
#define __LONG_LONG_MAX__ 9223372036854775807LL
#define __LONG_MAX__ 9223372036854775807L
#define __LP64__ 1
#define __MACH__ 1
#define __MMX__ 1
#define __NO_INLINE__ 1
#define __ORDER_BIG_ENDIAN__ 4321
#define __ORDER_LITTLE_ENDIAN__ 1234
#define __ORDER_PDP_ENDIAN__ 3412
#define __PCLMUL__ 1
#define __PIC__ 2
#define __POPCNT__ 1
#define __PRAGMA_REDEFINE_EXTNAME 1
#define __PTRDIFF_MAX__ 9223372036854775807L
#define __PTRDIFF_TYPE__ long int
#define __REGISTER_PREFIX__ 
#define __SCHAR_MAX__ 127
#define __SHRT_MAX__ 32767
#define __SIG_ATOMIC_MAX__ 2147483647
#define __SIG_ATOMIC_MIN__ (-__SIG_ATOMIC_MAX__ - 1)
#define __SIG_ATOMIC_TYPE__ int
#define __SIZEOF_DOUBLE__ 8
#define __SIZEOF_FLOAT__ 4
#define __SIZEOF_INT128__ 16
#define __SIZEOF_INT__ 4
#define __SIZEOF_LONG_DOUBLE__ 16
#define __SIZEOF_LONG_LONG__ 8
#define __SIZEOF_LONG__ 8
#define __SIZEOF_POINTER__ 8
#define __SIZEOF_PTRDIFF_T__ 8
#define __SIZEOF_SHORT__ 2
#define __SIZEOF_SIZE_T__ 8
#define __SIZEOF_WCHAR_T__ 4
#define __SIZEOF_WINT_T__ 4
#define __SIZE_MAX__ 18446744073709551615UL
#define __SIZE_TYPE__ long unsigned int
#define __SSE2_MATH__ 1
#define __SSE2__ 1
#define __SSE3__ 1
#define __SSE4_1__ 1
#define __SSE4_2__ 1
#define __SSE_MATH__ 1
#define __SSE__ 1
#define __SSSE3__ 1
#define __STDC_HOSTED__ 1
#define __STDC__ 1
#define __UINT16_C(c) c
#define __UINT16_MAX__ 65535
#define __UINT16_TYPE__ short unsigned int
#define __UINT32_C(c) c ## U
#define __UINT32_MAX__ 4294967295U
#define __UINT32_TYPE__ unsigned int
#define __UINT64_C(c) c ## ULL
#define __UINT64_MAX__ 18446744073709551615ULL
#define __UINT64_TYPE__ long long unsigned int
#define __UINT8_C(c) c
#define __UINT8_MAX__ 255
#define __UINT8_TYPE__ unsigned char
#define __UINTMAX_C(c) c ## UL
#define __UINTMAX_MAX__ 18446744073709551615UL
#define __UINTMAX_TYPE__ long unsigned int
#define __UINTPTR_MAX__ 18446744073709551615UL
#define __UINTPTR_TYPE__ long unsigned int
#define __UINT_FAST16_MAX__ 65535
#define __UINT_FAST16_TYPE__ short unsigned int
#define __UINT_FAST32_MAX__ 4294967295U
#define __UINT_FAST32_TYPE__ unsigned int
#define __UINT_FAST64_MAX__ 18446744073709551615ULL
#define __UINT_FAST64_TYPE__ long long unsigned int
#define __UINT_FAST8_MAX__ 255
#define __UINT_FAST8_TYPE__ unsigned char
#define __UINT_LEAST16_MAX__ 65535
#define __UINT_LEAST16_TYPE__ short unsigned int
#define __UINT_LEAST32_MAX__ 4294967295U
#define __UINT_LEAST32_TYPE__ unsigned int
#define __UINT_LEAST64_MAX__ 18446744073709551615ULL
#define __UINT_LEAST64_TYPE__ long long unsigned int
#define __UINT_LEAST8_MAX__ 255
#define __UINT_LEAST8_TYPE__ unsigned char
#define __USER_LABEL_PREFIX__ _
#define __VERSION__ "4.9.3"
#define __WCHAR_MAX__ 2147483647
#define __WCHAR_MIN__ (-__WCHAR_MAX__ - 1)
#define __WCHAR_TYPE__ int
#define __WINT_MAX__ 2147483647
#define __WINT_MIN__ (-__WINT_MAX__ - 1)
#define __WINT_TYPE__ int
#define __XSAVEOPT__ 1
#define __XSAVE__ 1
#define __amd64 1
#define __amd64__ 1
#define __code_model_small__ 1
#define __corei7_avx 1
#define __corei7_avx__ 1
#define __has_include(STR) __has_include__(STR)
#define __has_include_next(STR) __has_include_next__(STR)
#define __pic__ 2
#define __sandybridge 1
#define __sandybridge__ 1
#define __strong 
#define __tune_corei7_avx__ 1
#define __tune_sandybridge__ 1
#define __weak 
#define __x86_64 1
#define __x86_64__ 1

[ryandesign (Ryan Carsten Schmidt)]

Setting CXX=/opt/local//bin/x86_64-apple-darwin12-gcc-4.9.3 is unusual. Usually, you would set CXX=/opt/local/bin/g++-mp-4.9. Have you tried that already? Does it change anything?

Any particular reason you're using gcc 4.9.3? The latest stable version is 6.1.0, available in the gcc6 port.

[ryandesign (Ryan Carsten Schmidt)]

Replying to ryandesign@…:

Setting CXX=/opt/local//bin/x86_64-apple-darwin12-gcc-4.9.3 is unusual. Usually, you would set CXX=/opt/local/bin/g++-mp-4.9. Have you tried that already? Does it change anything?

I guess they're both hardlinks to the same file so it shouldn't make any difference. Still, /opt/local/bin/g++-mp-4.9 is the recommended form, since it does not vary by processor, OS version, or minor gcc version number.

[noloader (Jeffrey Walton)]

Replying to ryandesign@…:

Setting CXX=/opt/local/bin/x86_64-apple-darwin12-gcc-4.9.3 is unusual. Usually, you would set CXX=/opt/local/bin/g++-mp-4.9. Have you tried that already? Does it change anything?

Yeah, Uri Blumenthal told me it was wrong. I couldn't find a c++ compiler, so I installed GCC and hoped it would do the right thing based on file extensions:

$ port search 'g++'
No match for g++ found
$ port search '*g++*'
No match for *g++* found
$ port search 'g\+\+'
No match for g\+\+ found
$ port search '*g\+\+*'
No match for *g\+\+* found

Any particular reason you're using gcc 4.9.3? The latest stable version is 6.1.0, available in the gcc6 port.

Yes. I am setting up tests for MacPorts GCC compilers using a 4.x, 5.x and 6.x. They will all be tested eventually.

[noloader (Jeffrey Walton)]

This is probably related to -Wa,-q. When I originally tried to use it, I used it with a typo: -Wa,q. The typo resulted in:

$ /opt/local/bin/g++-mp-4.9 -Wa,q -c test.cxx
as:file(q) Can't open source file for input! No such file or directory.

At that point, I thought the compiler did not support the option.

Now that the typo has been corrected, it appears the option is supported:

$ /opt/local/bin/g++-mp-4.9 -Wa,-q -c test.cxx
/opt/local/bin/as: assembler (/opt/local/bin/clang) not installed

(The next mystery is why GCC cannot find one of the seven Clang's installed. I'll sort that out next on Stack Overflow).

[noloader (Jeffrey Walton)]

Its not clear to me if -Wa-q is the solution to the problem. We are trying to get our changes for MacPorts GCC tested now: ​Need MacPorts testers who use GCC.

I'll report back if we hear something from one of the users.

[Veence (Vincent)]

I am sorry to butt in, but this sound to me like the old 'as' story. GCC 4 use Apple-supplied /usr/bin/as (or /opt/local/bin/as for that matter):

as -v
Apple Inc version cctools-877.8, GNU assembler version 1.38

Which is so ancient it does not know about SSE 4 or AVX.

Clang has its own modern assembly, and can (maybe?) be used as a backend for GCC

[Veence (Vincent)]

Replying to vince@…:

I am sorry to butt in, but this sounds to me like the old 'as' story. GCC 4 use Apple-supplied /usr/bin/as (or /opt/local/bin/as for that matter):

as -v
Apple Inc version cctools-877.8, GNU assembler version 1.38

Which is so ancient it does not know about SSE 4 or AVX.

Clang has its own modern assembler, and can (maybe?) be used as a backend for GCC

[pgf]

Replying to Veence:

I am sorry to butt in, but this sounds to me like the old 'as' story. GCC 4 use Apple-supplied /usr/bin/as (or /opt/local/bin/as for that matter):

as -v
Apple Inc version cctools-877.8, GNU assembler version 1.38

Which is so ancient it does not know about SSE 4 or AVX.

The GCCs provided by MacPorts depend on cctools which in turn provides that really old as 1.38 (/opt/local/bin/as) which does not support newer instructions like AVX. That's why the compilation fails with the error no such instruction if one tries to enable those instructions with -march= , -mavx, etc... Indeed there are ports which fail to build for this reason depending on the host CPU, for example gdal with the variants +gccX and +perf on my machine (Core i7 Hasswell), because the latter append -march=native to configure.optflags.

Clang has its own modern assembly, and can (maybe?) be used as a backend for GCC

Yes, that's exactly what the -Wa,-q compiler option does. It instructs the assembler (/opt/local/bin/as) to switch to the clang integrated assembler (opt/local/bin/clang -integrated-as):

[foo@bar: ~]$ /opt/local/bin/as -v
Apple Inc version cctools-886, GNU assembler version 1.38

[foo@bar: ~]$ /opt/local/bin/as -v -q
clang version 3.9.0 (tags/RELEASE_390/final)
Target: x86_64-apple-darwin16.1.0
Thread model: posix
InstalledDir: /opt/local/libexec/llvm-3.9/bin
 "/opt/local/libexec/llvm-3.9/bin/clang" -cc1as -triple x86_64-apple-macosx10.12.0 -filetype obj -main-file-name - -target-cpu core2 -fdebug-compilation-dir /Users/foo -dwarf-debug-producer clang version 3.9.0 (tags/RELEASE_390/final) -dwarf-version=2 -mrelocation-model pic -o a.out -

The clang compiler provided by MacPorts must be installed and selected in order to use the integrated assembler:

[foo@bar: ~]$ sudo port select --show clang
The currently selected version for 'clang' is 'mp-clang-3.9'.

[foo@bar: ~]$ sudo port -f deactivate clang-3.9
--->  Deactivating clang-3.9 @3.9.0_1+analyzer
--->  Cleaning clang-3.9

[foo@bar: ~]$ /opt/local/bin/as -v -q
/opt/local/bin/as: assembler (/opt/local/bin/clang) not installed

The good news is that one doesn't need to mess with the compiler options. The same behaviour can be triggered setting the AS_INTEGRATED_ASSEMBLER environment variable:

[foo@bar: ~]$ AS_INTEGRATED_ASSEMBLER=1 /opt/local/bin/as -v
clang version 3.9.0 (tags/RELEASE_390/final)
Target: x86_64-apple-darwin16.1.0
Thread model: posix
InstalledDir: /opt/local/libexec/llvm-3.9/bin
 "/opt/local/libexec/llvm-3.9/bin/clang" -cc1as -triple x86_64-apple-macosx10.12.0 -filetype obj -main-file-name - -target-cpu core2 -fdebug-compilation-dir /Users/foo -dwarf-debug-producer clang version 3.9.0 (tags/RELEASE_390/final) -dwarf-version=2 -mrelocation-model pic -o a.out -

This is really useful because one doesn't need to change anything (Makefiles, scripts, etc...) to switch to the clang integrated assembler, just set that env variable. Indeed, a whole port can be compiled this way adding the env variable to the different keywords configure.env, build.env, test.env, etc...

[colinhowell (Colin Douglas Howell)]

I'm glad for pgf's workaround, because I was being bitten by this bug with the gcc7 port, using current MacPorts 2.4.2.

The gcc compiler proper only generates assembly language output, and it must invoke an assembler to assemble that output into binary object code. All of MacPorts' gcc ports have been configured to use /opt/local/bin/as, the old cctools assembler. So by the very nature of this problem, it will affect every GCC port that can generate instructions not recognized by that assembler, which means everything from gcc44 onward. With any of those compilers, this can happen either through using -march=native to generate optimal code for one's own machine, if that machine is reasonably new (one with a "Sandy Bridge" processor or newer, so around 2011 or newer), or through explicitly asking to generate optimal code for a newer architecture (e.g. -march=sandybridge), or through asking to use an instruction-set feature (e.g. -mavx) that would generate unrecognized instructions.

Therefore this ticket should be updated to include all the gcc ports from gcc44 on (except for cross-compilers for non-x86 architectures, of course) and to mention it still afflicts the latest MacPorts version. This is a serious problem and really should be fixed.

[colinhowell (Colin Douglas Howell)]

After further searching, I now see tickets #36389 and #54771 are also related to this same problem.

[mouse07410 (Mouse)]

For all the non-cross-compiled stuff, it would probably be advisable to set env variable AS_INTEGRATED_ASSEMBLER=1.

[kencu (Ken)]

I'm not certain which option would be better. We can leave things as they are, and use either the Wa,-q flag, or the AS_INTEGRATED_ASSEMBLER=1 environment variable to get the alternate behaviour (clang as assembler instead of as).

Or we could presumably change the gcc build (on Intel) to set clang as the assembler by default by specifying some version of clang here instead of as and then setting a build dep on that:

AS_FOR_TARGET=${prefix}/path/to/some/clang

HOWEVER, that could cause some irritating bootstrap issues and other issues...

My initial inclination is to leave things as they are, as there is an easy workaround to get the "clang as as" option, but none to go the other way...

[barracuda156]

Several crypto-related ports fail for x86_64 now on 10.6.8 when built with gcc11 (nettle, gnutls, nss). So there is basically no solution for gcc?