Bug 214431
| Summary: | head -r308247 for powerpc: clang 3.8.0 toolchain rejects "bc+" assembler notation | ||
|---|---|---|---|
| Product: | Base System | Reporter: | Mark Millard <marklmi26-fbsd> |
| Component: | bin | Assignee: | freebsd-toolchain (Nobody) <toolchain> |
| Status: | Closed Overcome By Events | ||
| Severity: | Affects Only Me | CC: | emaste |
| Priority: | --- | ||
| Version: | CURRENT | ||
| Hardware: | Any | ||
| OS: | Any | ||
Is this still the case with clang 6 in HEAD now? (In reply to Ed Maste from comment #1) I currently do not have a context for trying to build /usr/ports/math/gmp/ (or other such) for a powerpc or powerpc64 target environment via clang. It will be some time (unknown) before I'll again have such a context, possibly weeks or months. In more modern contexts, math/gmp builds fine for my experimental system-clang 8.0.0 based powerpc activity. Marking as Overcome By Events. |
[This would also apply to release/11.0.* , releng/11.0 , and stable/11 --that is if system-clang targeting powerpc was actually supported in 11.] [Note: I experiment with clang targeting powerpc and powerpc64 and report problems, including to llvm. clang 3.8.0 has various other issues for powerpc and is not for general use yet. For example: I use a modified powerpc kernel that has a so-called "red zone" on the stack for signal handling in order to deal with clang's stack handling ABI violations. This allows me to find and report other issues without waiting for the ABI fix.] If FreeBSD agrees that bc+ notation should be allowed in the clang toolchain then submittal to llvm would also be appropriate. On to the details/evidence. . . cc here is the powerpc system clang 3.8.0 from head -r308247 but I've seen this before for 3.8.0. The problem showed up in trying to build lang/gcc6, which in turn tried to build math/gmp: it is math/gmp where the failure happens. Other gcc* builds would also try to build math/gmp. The details are. . . --- divrem_2.lo --- /bin/sh ../libtool --mode=compile --tag=CC ../mpn/m4-ccas --m4="m4" cc -c -DHAVE_CONFIG_H -I. -I.. -D__GMP_WITHIN_GMP -I.. -DOPERATION_`echo divrem_2 | sed 's/_$//'` -pipe -g -fno-strict-aliasing `test -f 'divrem_2.asm' || echo './'`divrem_2.asm libtool: compile: ../mpn/m4-ccas --m4=m4 cc -c -DHAVE_CONFIG_H -I. -I.. -D__GMP_WITHIN_GMP -I.. -DOPERATION_divrem_2 -pipe -g -fno-strict-aliasing divrem_2.asm -fPIC -DPIC -o .libs/divrem_2.o . . . --- divrem_2.lo --- m4 -DHAVE_CONFIG_H -D__GMP_WITHIN_GMP -DOPERATION_divrem_2 -DPIC divrem_2.asm >tmp-divrem_2.s . . . --- divrem_2.lo --- cc -c -DHAVE_CONFIG_H -I. -I.. -D__GMP_WITHIN_GMP -I.. -DOPERATION_divrem_2 -pipe -g -fno-strict-aliasing tmp-divrem_2.s -fPIC -DPIC -o .libs/divrem_2.o cc: warning: argument unused during compilation: '-D HAVE_CONFIG_H' cc: warning: argument unused during compilation: '-D __GMP_WITHIN_GMP' cc: warning: argument unused during compilation: '-D OPERATION_divrem_2' cc: warning: argument unused during compilation: '-fno-strict-aliasing' cc: warning: argument unused during compilation: '-D PIC' tmp-divrem_2.s:122:2: error: unrecognized instruction mnemonic bc+ 12, 28, .L9 ^ tmp-divrem_2.s:139:2: error: unrecognized instruction mnemonic bc+ 12, 28, .L13 ^ *** [divrem_2.lo] Error code 1 make[4]: stopped in /usr/obj/portswork/usr/ports/math/gmp/work/gmp-5.1.3/mpn 1 error make[4]: stopped in /usr/obj/portswork/usr/ports/math/gmp/work/gmp-5.1.3/mpn *** [all-recursive] Error code 1 The clang 3.8.0 toolchain does not recognize the "+" notation for branch prediction control (Y-bit encoding) for bc instructions. # grep bc+ /usr/obj/portswork/usr/ports/math/gmp/work/gmp-5.1.3/mpn/* /usr/obj/portswork/usr/ports/math/gmp/work/gmp-5.1.3/mpn/divrem_2.asm: bc+ 12, 28, L(9) /usr/obj/portswork/usr/ports/math/gmp/work/gmp-5.1.3/mpn/divrem_2.asm: bc+ 12, 28, L(13) /usr/obj/portswork/usr/ports/math/gmp/work/gmp-5.1.3/mpn/tmp-divrem_2.s: bc+ 12, 28, .L9 /usr/obj/portswork/usr/ports/math/gmp/work/gmp-5.1.3/mpn/tmp-divrem_2.s: bc+ 12, 28, .L13 But there are other examples of the + notation in mpn: diveby3.asm: blelr+ cr7 divrem_2.asm: bgt+ cr7, L(4) divrem_2.asm: bge+ cr0, L(18) divrem_2.asm: blt+ cr7, L(24) divrem_2.asm: bgt+ cr7, L(28) These do not stop the math/gmp build. So it appears that some uses of the + notation are supported, just not bc+ . See "Branch Prediction" in https://developer.apple.com/library/content/documentation/DeveloperTools/Reference/Assembler/050-PowerPC_Addressing_Modes_and_Assembler_Instructions/ppc_instructions.html#//apple_ref/doc/uid/TP30000824-CJBDFIAE as an example documenting the + notation, including bc+ being allowed. Removing the two "+"s in divrem_2.asm's "bc+"s allows gmp to build. But who knows how many other ports or other software might have powerpc assembler notation with bc+ notation. I've not tried to use clang 3.8.0 for buildkernel for powerpc (or powerpc64), only buildworld and some ports. It could be that buildkernel could run into the bc+ notation issue for all I know. I have not tried clang 3.9.0 for powerpc (or powerpc64) yet. Of the fixes llvm has made for powerpc and powerpc64, I think FreeBSD's 3.9.0 project has yet to include the two most recent fixes. For powerpc one of the fixes completes the fix of the stack handling ABI violation as I remember. I will wait for that on powerpc for the 3.9.0 project. For powerpc64 it is softfloat support that was added (enabling libstand builds). Again I'll wait for the fix to be applied in the 3.9.0 project.