[rfa:ppc] Fix PPC/NBSD struct return; Was: userdef.exp regression for ppc?

[Jason R Thorpe]

On Sun, Jun 02, 2002 at 08:43:16PM -0400, Kevin B. Hendricks wrote:

 > So based on what I have read this code may have to be modified for NetBSD 
 > ppc.

I think your assumption is correct.

 > To prevent confusion, please specifiy whether or not you are (or will be) 
 > using small structure returns in registers for any of 
 > 
 > gcc 2.95.X
 > gcc 3.0.X
 > gcc 3.1 
 > 
 > for NetBSD ppc.

2.95.x -- NetBSD/powerpc was not supported in the stock GCC 2.95.3 release.
The native in-tree compiler for NetBSD/powerpc, which is 2.95.3-based,
returns small structures in registers.

3.0.x -- I don't know, I'd have to check.

3.1 -- *INCORRECTLY* returns small structures in memory.  3.1.1 will
correct the problem, and return small structures in registers, to match
the 2.95.3-based native in-tree compiler.

Please consider "returns small structures in registers, per the SVR4 ABI"
to be the expected behavior for NetBSD/powerpc.

 > Is there any value in keeping NetBSD PPC in sync with PPC Linux for these 
 > issues?  Does you decision here impact NetBSD's ppc ability to run PPC 
 > Linux binaries like the Blackdown JDK, etc under Linux emulation?

No, running binaries under Linux emulation will not be affected, since those
binaries are linked at run-time against Linux shared libraries.

 > Either way I would appreciate knowing your plans so that I can fix the 
 > bridge code in NetBSD for ppc (for both gcc 3.X and gcc 2.95.X).

See above.  If your bridge code for NetBSD/powerpc currently assumes the
"return in memory" behavior of Linux, then it is incorrect.

Attached are 4 files:

	test.c -- function which returns an 8 byte structure

	test.s-2.95.3-native -- asm output from the 2.95.3-based
	native compiler which will ship with NetBSD 1.6.  The output
	is the same as the 2.91-based compiler that NetBSD 1.5 shipped.

	test.s-3.2-broken -- asm output from gcc 3.1 and gcc-current
	before the compiler was fixed.

	test.s-3.2-working -- asm output from gcc 3.1(.1) and gcc-current
	after the compiler was fixed.

Note that I have checked the necessary fix into the GCC mainline and
the 3.1 branch (so the fix will be in 3.1.1).

-- 
        -- Jason R. Thorpe <thorpej@wasabisystems.com>
-------------- next part --------------
struct test_struct {
	int a;
	int b;
};

static struct test_struct test_struct = { 1,2 };

struct test_struct
test(void)
{

	return test_struct;
}
-------------- next part --------------
	.file	"test.c"
gcc2_compiled.:
	.section	".sdata","aw"
	.align 2
	.type	 test_struct,@object
	.size	 test_struct,8
test_struct:
	.long 1
	.long 2
	.section	".text"
	.align 2
	.globl test
	.type	 test,@function
test:
	lis 9,test_struct@ha
	la 9,test_struct@l(9)
	lwz 3,0(9)
	lwz 4,4(9)
	blr
.Lfe1:
	.size	 test,.Lfe1-test
	.ident	"GCC: (GNU) 2.95.3 20010315 (release) (NetBSD nb1)"
-------------- next part --------------
	.file	"test.c"
	.section	".data"
	.align 2
	.type	test_struct,@object
	.size	test_struct,8
test_struct:
	.long	1
	.long	2
	.section	".text"
	.align 2
	.globl test
	.type	test,@function
test:
	lis 11,test_struct@ha
	la 11,test_struct@l(11)
	lfd 0,0(11)
	stfd 0,0(3)
	blr
.Lfe1:
	.size	test,.Lfe1-test
	.ident	"GCC: (GNU) 3.2 20020602 (experimental)"
-------------- next part --------------
	.file	"test.c"
	.section	".data"
	.align 2
	.type	test_struct,@object
	.size	test_struct,8
test_struct:
	.long	1
	.long	2
	.section	".text"
	.align 2
	.globl test
	.type	test,@function
test:
	lis 9,test_struct@ha
	la 9,test_struct@l(9)
	lwz 3,0(9)
	lwz 4,4(9)
	blr
.Lfe1:
	.size	test,.Lfe1-test
	.ident	"GCC: (GNU) 3.2 20020602 (experimental)"