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[Gcl-devel] GCL and GC on hppa

From: Camm Maguire
Subject: [Gcl-devel] GCL and GC on hppa
Date: Mon, 30 Oct 2006 13:38:12 -0500
User-agent: SEMI/1.14.3 (Ushinoya) FLIM/1.14.3 (Unebigory ōmae) APEL/10.3 Emacs/21.2 (i386-debian-linux-gnu) MULE/5.0 (SAKAKI)

Greetings!  Some time ago, you graciously contributed the following
register flushing code to GCL:

#if defined(__hppa__) /* Courtesy of Lamont Jones */
/* the calling sequence */
struct regs {
        void *callee_saves[16];
void hppa_save_regs(struct regs);

/* the code */

        asm(".export hppa_save_regs, entry");
        asm(".label     hppa_save_regs");

        asm("stw        %r3,0(%arg0)");
        asm("stw        %r4,4(%arg0)");
        asm("stw        %r5,8(%arg0)");
        asm("stw        %r6,12(%arg0)");
        asm("stw        %r7,16(%arg0)");
        asm("stw        %r8,20(%arg0)");
        asm("stw        %r9,24(%arg0)");
        asm("stw        %r10,28(%arg0)");
        asm("stw        %r11,32(%arg0)");
        asm("stw        %r12,36(%arg0)");
        asm("stw        %r13,40(%arg0)");
        asm("stw        %r14,44(%arg0)");
        asm("stw        %r15,48(%arg0)");
        asm("stw        %r16,52(%arg0)");
        asm("stw        %r17,56(%arg0)");
        asm("bv 0(%rp)");
        asm("stw        %r18,60(%arg0)");


I notice in gdb on paer that there are actually quite a few more regs
which look like they might contain data pointers:

(gdb) i reg
flags          0x0      0
r1             0x286494 2647188
rp             0xa9377  693111
r3             0x2      2
r4             0xc02a1f70       3223986032
r5             0x493c94 4799636
r6             0x286ca8 2649256
r7             0x4b3c94 4930708
r8             0x32cc94 3329172
r9             0x61aad4 6400724
r10            0x0      0
r11            0x4b3fa8 4931496
r12            0x0      0
r13            0x0      0
r14            0x0      0
r15            0x0      0
r16            0x0      0
r17            0x0      0
r18            0x0      0
r19            0x4dc9d8 5097944
r20            0x28     40
r21            0x0      0
r22            0x32c748 3327816
---Type <return> to continue, or q <return> to quit--- 
r23            0x0      0
r24            0x278d5e 2592094
r25            0x2      2
r26            0xc02a1f0c       3223985932
dp             0x26bc94 2538644
ret0           0x239800 2332672
ret1           0x0      0
sp             0xc02a2100       3223986432
r31            0xa91e3  692707
sar            0x1c     28
pcoqh          0xa9377  693111
pcsqh          0x0      0
pcoqt          0xa937b  693115
pcsqt          0x0      0
eiem           0x0      0
iir            0x0      0
isr            0x0      0
ior            0x0      0
ipsw           0x4000b  262155
goto           0x0      0
sr4            0x0      0
sr0            0x0      0
sr1            0x0      0

I know you've already responded that nothing recent should have
changed this, but I am getting definite GC failure at modest gcc
optimization levels which used to work on hppa, and am wondering
perhaps if more recent compilers are using more registers.

Separately, it appears that hppa has joined ia64 now in its handling
of function descriptors, i.e. there being some sort of trampoline in a
dynamically loaded shared memory area.  Thankfully we have a work
around for ia64 which appears to work here too (GCL needs to be able
to dump unchanging function addresses into an executable file image).
I bring this up because ia64 is the only other arch with special gc
support in GCL:

#if defined(__ia64__)
        asm("        .text");
        asm("        .psr abi64");
        asm("        .psr lsb");
        asm("        .lsb");
        asm("        .text");
        asm("        .align 16");
        asm("        .global GC_save_regs_in_stack");
        asm("        .proc GC_save_regs_in_stack");
        asm("        .body");
        asm("        flushrs");
        asm("        ;;");
        asm("        mov r8=ar.bsp");
        asm("        br.ret.sptk.few rp");
        asm("        .endp GC_save_regs_in_stack");

void * GC_save_regs_in_stack();

There are two stacks which need saving on ia64.  Could something
similar have been added to hppa too?

Take care, and thanks again!

Camm Maguire                                            address@hidden
"The earth is but one country, and mankind its citizens."  --  Baha'u'llah

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