On 02/06/2020 05:42, Sebastian Riedel wrote:
I don’t use stm8, but when I looked through it’s constraint functions,
I saw that it allows things like notUsed('z')
And after a quick look into the OP codes, it looks like %1 and %2
could also be XH/YH/XL/YL/SP, which doesn’t seem to be supported by mov.
Ah, yes, I see there can be notUsed('n') and notUsed('z'); quite
literally the first few rules in the STM8 peeph.def file use them -
don't know how I didn't see!
The dst/src not being XL/XH/etc. is not really the only restriction that
should be made - hence why I said I think the rule would need a
restriction of %1 and %2 being only direct memory addresses (either
8-bit 'shortmem' or 16-bit 'longmem'). MOV only can be used in those two
contexts (well, also immediate value to a memory location).
Perhaps it should be looked at the opposite way, and any LD instruction
*not* involving X, Y, SP, an immediate value or indirect addressing in
the operands is a candidate. How to do that? Maybe with notSimilar()? As
far as I can see, it does substring matching within an operand, but I
don't see any examples of its use in any peeph.def files of any
platform, so I'm not sure. Maybe like this:
replace {
ld a, %1
ld %2, a
} by {
mov %2, %1
} if notUsed('a'), notUsed('n'), notUsed('z'), notSimilar(%1 'x' 'y'
'sp' '#' '[' ']')
Will that work? Should it also have a "restart"?
On 02/06/2020 13:10, Philipp Klaus Krause wrote:
Compiling with --fverbose-asm (and sometimes --no-peep --i-code-in-asm)
often can help with such questions.
Also, for people on the list, it could help to see what CAN_PSR is (the
generated code might depend on use of __at vs. casting an integer into
an address).
Here is what was in the assembly listing when compiled with all those
options:
; can.c: 451: prev_page = CAN_PSR;
; ic: 44: _can_rx_isr_prev_page_65537_99 [k33 lr0:0 so:0]{ ia1
a2p0 re0 rm0 nos0 ru0 dp0}{unsigned-char auto} = @[0x5427
{volatile-unsigned-char generic* literal} + 0x0 {const-unsigned-char
literal}]
; genPointerGet
ld a, 0x5427
ld _can_rx_isr_prev_page_65537_99+0, a
; can.c: 513: CAN_PSR = prev_page;
; ic: 150: *[0x5427 {volatile-unsigned-char generic* literal}] =
_can_rx_isr_prev_page_65537_99 [k33 lr0:0 so:0]{ ia0 a2p0 re0 rm0 nos0
ru0 dp0}{unsigned-char auto}
; genPointerSet
mov 0x5427+0, _can_rx_isr_prev_page_65537_99+0
The prev_page variable is declared as: static can_page_enum_t prev_page;
And can_page_enum_t is:
typedef enum {
CAN_PG_TX_MBOX_0 = 0,
// ...
CAN_PG_RX_FIFO = 7
} can_page_enum_t;
CAN_PSR is defined as: #define CAN_PSR (*(volatile uint8_t *)(0x5427))
Regards,
Basil Hussain
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