Hello
The _divuint function use a bool variables, but this is not optimal:
- this force the use of the "T" reg as soon as a 16bit division is used on
mcs51, thus potentially reducing the stack size up to 24 bytes.
- This force the compiler to use a bit, which produce suboptimal code
- This does not reduce stack useage as the compiler can allocate the bool
variable to a register
The following patch use a unsigned char for the boolean variable the generated
code is changed as following for the large stack auto code model:
@@ -109,7 +95,7 @@
;x Allocated to registers r6 r7
;reste Allocated to registers r4 r5
;count Allocated to registers r3
-;c Allocated to registers b0
+;c Allocated to registers r2
;------------------------------------------------------------
; _divuint.c:155: _divuint (unsigned int x, unsigned int y)
; -----------------------------------------
@@ -139,8 +125,6 @@
rl a
anl a,#0x01
mov r2,a
- add a,#0xff
- mov b0,c
; _divuint.c:165: x <<= 1;
mov a,r7
xch a,r6
@@ -156,7 +140,8 @@
rlc a
mov r5,a
; _divuint.c:167: if (c)
- jnb b0,00102$
+ mov a,r2
+ jz 00102$
; _divuint.c:168: reste |= 1;
orl ar4,#0x01
00102$:
On cc253x SoC this lead to a reduction of 4 byte in code size and 5 cycle per
loop iteration.
Thanks,
Philippe
Index: device/lib/_divuint.c
===================================================================
--- device/lib/_divuint.c (révision 7100)
+++ device/lib/_divuint.c (copie de travail)
@@ -156,7 +156,7 @@
{
unsigned int reste = 0;
unsigned char count = 16;
- BOOL c;
+ unsigned char c;
do
{
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