On Monday, September 12, 2016 at 9:58:58 PM UTC-6, Michael Hudson-Doyle wrote: > > > > On 13 September 2016 at 13:43, <pcj...@gmail.com <javascript:>> wrote: > >> I'm implementing cross-compilation support in rules_go >> <https://github.com/bazelbuild/rules_go>. This takes a low-level >> approach to building golang targets that involves use of the individual >> toolchain components such as 'go tool asm', 'go tool compile', 'go tool >> link', etc... >> >> Cross-compilation of pure-go inputs is working swimmingly. However, I'm >> wondering how to cross-compile assembly inputs correctly. Consider the >> following assembly file that defines an 'add' method. >> >> *#include "textflag.h"* >> >> *TEXT ·add(SB),NOSPLIT,$0* >> * MOVQ x+0(FP), BX* >> * MOVQ y+8(FP), BP* >> * ADDQ BP, BX* >> * MOVQ BX, ret+16(FP)* >> * RET* >> >> For example, this works: >> >> *$ go tool asm -I $(go env GOROOT)/pkg/include -o add.o add.s* >> *$ hexdump add.o* >> >> *0000000 67 6f 20 6f 62 6a 65 63 74 20 64 61 72 77 69 6e* >> >> *0000010 20 61 6d 64 36 34 20 67 6f 31 2e 36 2e 32 0a 21* >> >> *0000020 0a 00 00 67 6f 31 33 6c 64 01 00 fe 02 0c 22 22* >> >> *0000030 2e 61 64 64 00 00 40 00 00 40 48 8b 5c 24 08 48* >> >> *0000040 8b 6c 24 10 48 01 eb 48 89 5c 24 18 c3 cc cc cc* >> >> *0000050 cc cc cc cc cc cc cc cc cc cc 00 ff ff ff ff 0f* >> >> *0000060 00 02 00 00 06 02 20 00 06 02 20 00 16 0a 05 02* >> >> *0000070 05 02 03 02 05 02 0e 00 00 02 28 22 22 2e 61 64* >> >> *0000080 64 2e 61 72 67 73 5f 73 74 61 63 6b 6d 61 70 00* >> >> *0000090 00 02 52 2f 55 73 65 72 73 2f 70 63 6a 2f 67 69* >> >> *00000a0 74 68 75 62 2f 67 72 70 63 2d 67 72 65 65 74 65* >> >> *00000b0 72 74 69 6d 65 72 2f 61 64 64 2e 73 02 ff ff 67* >> >> *00000c0 6f 31 33 6c 64 * >> >> *00000c5* >> >> >> Given the magic of "goose" and "garch" (and it is magical), I expected >> this to work: >> >> *$ env GOOS=linux GOARCH=arm go tool asm -I $(go env GOROOT)/pkg/include >> -o add.o add.s* >> >> *add.s:4: unrecognized instruction "MOVQ"* >> >> *add.s:5: unrecognized instruction "MOVQ"* >> >> *add.s:6: unrecognized instruction "ADDQ"* >> >> *add.s:7: unrecognized instruction "MOVQ"* >> >> *asm: asm: assembly of add.s failed* >> > > The problem here is that MOVQ is not a valid instruction for arm. >
I see (apologies for limited knowledge of assembly). My interpretation of golang's assembly is that it represents an intermediate pseudo-language that is transformed via "instruction selection" to a concrete form. Therefore, is it possible to re-write the above to a cross-compilable form? If so, is this generalizable? > > >> This was the initial issue for this post. However, I figured that part >> out (the std library needs to be compiled first). So this works: >> >> *$ env GOOS=linux GOARCH=arm go install std && go tool asm -I $(go env >> GOROOT)/pkg/include -o add.o add.s* >> > > And here, the GOOS/GOARCH settings only apply to the first command that is > run, not the asm invocation. > > That makes sense... I should get up and walk around more often. No wonder the file is always the same! > Cheers, > mwh > > >> However, now I'm curious why whatever platform GOOS_GOARCH I choose, the >> file is exactly the same (see hexdump above). >> >> So i'm wondering why that is. Am I doing something wrong? If not, why >> are GOOS and GOARCH needed at all at this stage? >> >> Thanks for helping me clear this up, and thanks for golang! >> Paul >> >> -- >> You received this message because you are subscribed to the Google Groups >> "golang-nuts" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to golang-nuts...@googlegroups.com <javascript:>. >> For more options, visit https://groups.google.com/d/optout. >> > > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
