[cfe-dev] Getting started with clang

[Mike Stump]

On Aug 17, 2009, at 8:46 AM, Robert Wuest wrote:
> I'm just getting started with clang and having some problems.  I'm
> trying to build a compiler to run on x8_64 and gen code for the
> powerpc.

The normal clang can do that just fine.

> This definitely produces a working native compiler as seen here:
>
> $ clang hello.c
> $ ./a.out
> Hello, world
>
> However, when I try the '-arch ppc' option, it still only produces
> x86_64 code:

You sure?  See below...  Try the -S option, seeing is believing.

> $ rm a.out
> $ clang -arch ppc hello.c
> clang: warning: argument unused during compilation: '-arch ppc'
> $ ./a.out
> Hello, world

> Have I missed something?

$ cat >t.c
int main() {
   printf("Hello World!\n");
}
mrs $ clang t.c -w
mrs $ a.out
Hello World!
$ file a.out
a.out: Mach-O 64-bit executable x86_64
mrs $ clang -arch ppc t.c -w
mrs $ a.out
Hello World!
mrs $ file a.out
a.out: Mach-O executable ppc
mrs $ clang -arch ppc t.c -w -o - -S
	.machine ppc
	.section	__TEXT,__textcoal_nt,coalesced,pure_instructions
	.section	__TEXT,__picsymbolstub1,symbol_stubs,pure_instructions,32
	.section	__TEXT,__text,regular,pure_instructions


	.globl	_main
	.align	4
_main:
	mflr r0
	stw r31, 20(r1)
	stw r0, 8(r1)
	stwu r1, -64(r1)
	mr r31, r1
	bl "L1$pb"
"L1$pb":
	mflr r2
	li r3, 0
	addis r2, r2, ha16(L_.str-"L1$pb")
	stw r3, 60(r31)
	la r2, lo16(L_.str-"L1$pb")(r2)
	mr r3, r2
	bl L_printf$stub
	mr r2, r3
	lwz r2, 60(r31)
	mr r3, r2
	addi r1, r1, 64
	lwz r0, 8(r1)
	lwz r31, 20(r1)
	mtlr r0
	blr
	.section	__TEXT,__picsymbolstub1,symbol_stubs,pure_instructions,32
	.align	4
L_printf$stub:
	.indirect_symbol _printf
	mflr r0
	bcl 20,31,L_printf$stub$tmp
L_printf$stub$tmp:
	mflr r11
	addis r11,r11,ha16(L_printf$lazy_ptr-L_printf$stub$tmp)
	mtlr r0
	lwzu r12,lo16(L_printf$lazy_ptr-L_printf$stub$tmp)(r11)
	mtctr r12
	bctr
	.section	__DATA,__la_symbol_ptr,lazy_symbol_pointers
L_printf$lazy_ptr:
	.indirect_symbol _printf
	.long dyld_stub_binding_helper

	.subsections_via_symbols
	.section	__TEXT,__cstring,cstring_literals
L_.str:
	.asciz	"Hello World!\n"