Hi, Please find below a simple patch which optimizes the loading of immediate value by using the clrw or clrb instruction in case a 0x00 is being loaded into the register. The patch replaces movw/mov instruction with the smaller clrw/clrb instruction. The clrw and clrb generates only 1 byte of opcode as compared to 3 or 2 bytes for movw and mov.
There is a total of about 94 bytes code size improvement with this patch in
these libgcc routines.
The following routines have improved code size,
___mulsi3 : 2 bytes
___divsi3 : 20 bytes
___modsi3 : 20 bytes
___divhi3 : 10 bytes
___modhi3 : 10 bytes
___parityqi_internal : 2 bytes
__int_cmpsf : 2 bytes
___fixsfsi : 5 bytes
___fixunssfsi : 2 bytes
___floatsisf : 6 bytes
_int_unpack_sf : 1 bytes
___addsf3 : 5 bytes
__rl78_int_pack_a_r8 : 2 bytes
___mulsf3 : 2 bytes
___divsf3 : 3 bytes
__gcc_bcmp : 2 bytes
I have also attached a draft version of a similar patch
(rl78_libgcc_optimize_draft.patch), which goes further and
removes movw immediate to other saddr registers and replaces them with 2
instructions, i.e.
START_FUNC ___modhi3
;; r8 = 4[sp] % 6[sp]
- movw de, #0
+ clrw ax
+ movw de,ax
mov a, [sp+5]
This patch improves code size by 1 byte for each such substitution, however
does add an extra clock cycle.
We may consider this patch in case we are purely looking for code size
improvement, assuming the libraries
are built with -Os. This shows a total of 134 bytes improvement in code size.
Patch1: rl78_libgcc_optimize_clrw.patch - 94 bytes improvement in code size.
Patch2: rl78_libgcc_optimize_draft.patch - 134 bytes improvement in code size.
Kindly review this patch and let me know what you think.
This is regression tested for rl78 -msim.
Best Regards,
Kaushik
p.s. Kindly ignore any disclaimers at end of this e-mail as they are
auto-inserted.
Apologies for the same.
2016-02-05 Kaushik Phatak <kaushik.pha...@kpit.com>
* config/rl78/bit-count.S: Use clrw/clrb where possible.
* config/rl78/cmpsi2.S: Likewise.
* config/rl78/divmodhi.S Likewise.
* config/rl78/divmodsi.S Likewise.
* config/rl78/fpbit-sf.S Likewise.
* config/rl78/fpmath-sf.S Likewise.
* config/rl78/mulsi3.S Likewise.
Index: libgcc/config/rl78/bit-count.S
===================================================================
--- libgcc/config/rl78/bit-count.S (revision 3174)
+++ libgcc/config/rl78/bit-count.S (working copy)
@@ -139,7 +139,7 @@
xor1 cy, a.5
xor1 cy, a.6
xor1 cy, a.7
- movw ax, #0
+ clrw ax
bnc $1f
incw ax
1:
@@ -190,7 +190,7 @@
movw ax, sp
addw ax, #4
movw hl, ax
- mov a, #0
+ clrb a
1:
xch a, b
mov a, [hl]
@@ -207,7 +207,7 @@
bnz $1b
mov x, a
- mov a, #0
+ clrb a
movw r8, ax
ret
END_FUNC ___popcountqi_internal
Index: libgcc/config/rl78/cmpsi2.S
===================================================================
--- libgcc/config/rl78/cmpsi2.S (revision 3174)
+++ libgcc/config/rl78/cmpsi2.S (working copy)
@@ -162,8 +162,8 @@
;; They differ. Subtract *S2 from *S1 and return as the result.
mov x, a
- mov a, #0
- mov r9, #0
+ clrb a
+ clrb r9
subw ax, r8
1:
movw r8, ax
Index: libgcc/config/rl78/divmodhi.S
===================================================================
--- libgcc/config/rl78/divmodhi.S (revision 3174)
+++ libgcc/config/rl78/divmodhi.S (working copy)
@@ -576,7 +576,7 @@
.macro NEG_AX
movw hl, ax
- movw ax, #0
+ clrw ax
subw ax, [hl]
movw [hl], ax
.endm
Index: libgcc/config/rl78/divmodsi.S
===================================================================
--- libgcc/config/rl78/divmodsi.S (revision 3174)
+++ libgcc/config/rl78/divmodsi.S (working copy)
@@ -952,10 +952,10 @@
.macro NEG_AX
movw hl, ax
- movw ax, #0
+ clrw ax
subw ax, [hl]
movw [hl], ax
- movw ax, #0
+ clrw ax
sknc
decw ax
subw ax, [hl+2]
Index: libgcc/config/rl78/fpbit-sf.S
===================================================================
--- libgcc/config/rl78/fpbit-sf.S (revision 3174)
+++ libgcc/config/rl78/fpbit-sf.S (working copy)
@@ -117,7 +117,7 @@
call $!__int_iszero
bnz $2f
;; At this point, both args are zero.
- mov a, #0
+ clrb a
ret
2:
@@ -151,7 +151,7 @@
bc $ybig_cmpsf ; branch if X < Y
bnz $xbig_cmpsf ; branch if X > Y
- mov a, #0
+ clrb a
ret
xbig_cmpsf: ; |X| > |Y| so return A = 1 if pos, 0xff if neg
@@ -285,7 +285,7 @@
movw r10, #0x7fff
ret
;; -inf
-2: mov r8, #0
+2: clrb r8
mov r10, #0x8000
ret
@@ -302,10 +302,10 @@
clr1 a.7
call $!__int_fixunssfsi
- movw ax, #0
+ clrw ax
subw ax, r8
movw r8, ax
- movw ax, #0
+ clrw ax
sknc
decw ax
subw ax, r10
@@ -410,7 +410,7 @@
set1 a.7
;; Clear B:C:R12:R13
- movw bc, #0
+ clrw bc
movw r12, #0
;; Shift bits from the mantissa (A:X:R10) into (B:C:R12:R13),
@@ -482,10 +482,10 @@
;; If negative convert to positive ...
movw hl, ax
- movw ax, #0
+ clrw ax
subw ax, bc
movw bc, ax
- movw ax, #0
+ clrw ax
sknc
decw ax
subw ax, hl
@@ -533,7 +533,7 @@
bnz $1f
movw ax, bc
cmpw ax, #0
- movw ax, #0
+ clrw ax
bnz $1f
;; Return 0.0
Index: libgcc/config/rl78/fpmath-sf.S
===================================================================
--- libgcc/config/rl78/fpmath-sf.S (revision 3174)
+++ libgcc/config/rl78/fpmath-sf.S (working copy)
@@ -87,7 +87,7 @@
or a, #0x80
mov A_FRAC_H, a
- mov a, #0
+ clrb a
mov A_FRAC_HH, a
;; rounding-bit-shift
@@ -273,7 +273,7 @@
;; "zero out" b
movw ax, A_EXP
movw B_EXP, ax
- movw ax, #0
+ clrw ax
movw B_FRAC_L, ax
movw B_FRAC_H, ax
br $5f
@@ -281,7 +281,7 @@
;; "zero out" a
movw ax, B_EXP
movw A_EXP, ax
- movw ax, #0
+ clrw ax
movw A_FRAC_L, ax
movw A_FRAC_H, ax
@@ -379,7 +379,7 @@
bt a.7, $.L706
;; subtraction was positive
- mov a, #0
+ clrb a
mov A_SIGN, a
br $.L712
@@ -543,7 +543,7 @@
or a, A_FRAC_H
or a, A_FRAC_HH
bnz $1f
- movw ax, #0
+ clrw ax
movw A_EXP, ax
1:
mov a, A_FRAC_H
@@ -682,7 +682,7 @@
movw ax, B_FRAC_H
movw [sp+10], ax
- movw ax, #0
+ clrw ax
movw [sp+4], ax
movw [sp+6], ax
movw [sp+12], ax
@@ -867,7 +867,7 @@
and a, #0x80
mov r11, a
movw r8, #0
- mov r10, #0
+ clrb r10
ret
1:
@@ -930,7 +930,7 @@
movw ax, B_FRAC_H
movw [sp+10], ax
- movw ax, #0
+ clrw ax
movw [sp+0], ax
movw [sp+2], ax
movw [sp+12], ax
Index: libgcc/config/rl78/mulsi3.S
===================================================================
--- libgcc/config/rl78/mulsi3.S (revision 3174)
+++ libgcc/config/rl78/mulsi3.S (working copy)
@@ -148,7 +148,7 @@
movw ax, bc
.Lmul_hisi_top:
- movw bc, #0
+ clrw bc
.Lmul_hisi_loop:
shrw ax, 1
rl78_libgcc_optimize_draft.patch
Description: rl78_libgcc_optimize_draft.patch
rl78_libgcc_optimize_clrw.patch
Description: rl78_libgcc_optimize_clrw.patch
