[LLVMdev] Problems with paged registers and seperated program and data memory

[Philipp Strobel]

Hi

I'm hacking my own backend for a small 16 bit microprocessor. I took some code from the msp430 backend, because there are some similarities.

But there are some features, I couldn't find a solution yet:

1. Paged Registers
The register set is a bit complicated:
it has 64 general purpose registers, and the upper 32 registers are paged registers with 8 pages. The lower 32 registers are always page 0. So I can use up to 256 registers. I also can use some of these paged registers as special registers for communication with a co-processor.
There are also 16 data aliases and 16 address aliases, that can be paged too. These aliases can page to 0..15, 16..31, 32..47 or 48..63 of the 64 general purpose registers. These aliases are only used by load and store operations.

Right now I can use 64 registers and the aliases are hard coded, for most apllication this is ok, but there are some applications that require more registers. Is there support for paged registers or is there a way to describe it in a simple way?

2. Seperated program and data memory
I have the possibility to load data from program memory and data memory, that are seperated. I have different load operations in assembler for these two cases. Right now, I already create code, that loads data from both but I don't know how to check, which load operation I have to use.

Small example of a load from program memory:

C Code:
...
int values[] = {25, 13, 19, 31, 11, 99, 21, 17};
...


Assembler:
...
	mov		_ZZ4mainE6values, R0
	add		2, R0
...
	mov		R0, R16
	ld		A0, D0                  <-- this is my bad load
                                                   operation, that loads everything
                                                   A0 is alias for R0
                                                   D0 is alias for R16
                                                   this should be "lp A0, D0"
...
...
_ZZ4mainE6values:
	.short	25                      # 0x19
	.short	13                      # 0xd
	.short	19                      # 0x13
	.short	31                      # 0x1f
	.short	11                      # 0xb
	.short	99                      # 0x63
	.short	21                      # 0x15
	.short	17                      # 0x11
	.cc_bottom _ZZ4mainE6values.data


Thanks,
Philipp
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