在 2022/3/8 上午2:17, Richard Sandiford 写道:
[…]
+/* This definition replaces the formerly used 'm' constraint with a
+ different constraint letter in order to avoid changing semantics of
+ the 'm' constraint when accepting new address formats in
+ TARGET_LEGITIMATE_ADDRESS_P. The constraint letter defined here
+ must not be used in insn definitions or inline assemblies. */
+#define TARGET_MEM_CONSTRAINT 'w'
Do you need to do this for a new port like Loongson? It looks like
TARGET_LEGITIMATE_ADDRESS_P accepts all valid forms of address,
including reg+reg (good!), so shouldn't "m" accept them too?
If there is already existing code that assumes that "m" is never indexed
then the definition obviously makes sense. But if you don't know of any
such code then it would be better to make "m" accept all the things that
TARGET_LEGITIMATE_ADDRESS_P does (by removing this definition).
Hi, Richard:
LoongArch supports memory modes as follows:
mode
1. base + index
2. base + imm12
3. base + imm16 (immediate 4-byte alignment)
4. base + 0
Because 'base + imm12' is most case, so we defined it to 'm'.
Thanks.
