GCC-SH: shad problem and memset optimization

[Toshi Morita]

   host: i386-linux
 target: sh-elf
version: CVS 10/12/2000
options: -O2 -m4-single-only -ml

When jidctfst.i from stress-1.16 is compiled, the following code is emitted:

1) GCC fails to notice that "shad" doesn't destroy first register, and
   reloads it multiple times unnecessarily.

The shad insn appears to be defined like this:

(define_insn "ashrsi3_d"
  [(set (match_operand:SI 0 "arith_reg_operand" "=r")
        (ashiftrt:SI (match_operand:SI 1 "arith_reg_operand" "0")
                     (neg:SI (match_operand:SI 2 "arith_reg_operand" "r"))))]
  "TARGET_SH3"
  "shad %2,%0"
  [(set_attr "type" "dyn_shift")])

I'm wondering if CSE is having trouble with the embedded neg:SI...

_jpeg_idct_ifast:
...
.L66:
...
        mov     #-5,r1          <- here
        shad    r0,r6
        mov.w   .L55,r0
        add     r2,r6
        mov.w   .L58,r2
        shad    r1,r12
        sub     r7,r6
        add     r14,r0
        mov     #-5,r7          <- here
        mov.l   @(16,r0),r0
        and     r2,r12
        sub     r6,r4
        mov.b   @(r0,r12),r1
        add     r4,r5
        mov.b   r1,@r3
        mov     #-5,r1          <- here
        add     #7,r3
        shad    r1,r9

Same function in same file: 

2) r1 is unnecessarily zero-extended.

3) addressing modes could be improved

I'm surprised GCC isn't doing this here; I could've sworn
it's done this optimization on other pieces of code.

.L38:
        mov     #-5,r7
        mov.w   .L55,r0
        mov.w   .L58,r8
        shad    r7,r6
        add     r14,r0
        mov.l   @(16,r0),r0
        and     r8,r6
        mov.b   @(r0,r6),r1

        extu.b  r1,r1                   add     #8,r3
        mov.b   r1,@r3                  mov.b   r1,@-r3
        add     #1,r3
        mov.b   r1,@r3                  mov.b   r1,@-r3
        add     #1,r3
        mov.b   r1,@r3                  mov.b   r1,@-r3
        add     #1,r3
        mov.b   r1,@r3                  mov.b   r1,@-r3
        add     #1,r3
        mov.b   r1,@r3                  mov.b   r1,@-r3
        add     #1,r3
        mov.b   r1,@r3                  mov.b   r1,@-r3
        add     #1,r3
        mov.b   r1,@r3                  mov.b   r1,@-r3
        add     #1,r3
        mov.b   r1,@r3                  mov.b   r1,@-r3
                                        add     #7,r3
        mov.w   .L55,r1
        add     r14,r1
        mov.l   @(12,r1),r2
        add     #32,r2
        bra     .L31
        mov.l   r2,@(12,r1)
        .align 5

Toshi