On 13 September 2016 at 13:43, <pcj...@gmail.com> 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 $(go env GOROOT)/pkg/include > -o add.o add.s* > > *add.s:4: unrecognized instruction "MOVQ"* > > *add.s:5: unrecognized instruction "MOVQ"* > > *add.s:6: unrecognized instruction "ADDQ"* > > *add.s:7: unrecognized instruction "MOVQ"* > > *asm: asm: assembly of add.s failed* >
The problem here is that MOVQ is not a valid instruction for arm. > This was the initial issue for this post. However, I figured that part > out (the std library needs to be compiled first). So this works: > > *$ 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. 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+unsubscr...@googlegroups.com. > 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.
