On 09/03/09 09:44, Dave Korn wrote:
Also note that reload does not distinguish between a load and a store when verifying the legitimacy of an address, meaning that reload doesn't handle cases where a particular addressing mode is available for loads, but not stores (or vice-versa).Mohamed Shafi wrote:The restriction is that if the base register is not Stack Pointer then this kind of address cannot come in a load instruction but only in store instruction. To implement this i added constrains for all supported memory operations in QImode. So the pattern is as follows (define_insn "movqi" [(set (match_operand:QI 0 "nonimmediate_operand" "=b,b,d,t,d, b,Ss0, Ss1, a,Se1, Sb2, b,Sd3, d,Se0") (match_operand:QI 1 "general_operand" "I,L,d,d,t, Ss0,b, b, Se1,a, b, Sd3,b, Se0,d"))] where d is data registers a is address registers b is data and address registers Sb2 is Rn + offset addressing mode Sd3 is SP + offset addressing mode Se0 - (Rn), (Rn)+, (Rn)-, (Rn + Ri) and Post modify register addressing mode Se1 - Se0 excluding Post modify register addressing mode I believe that there are enough combinations available for the reload to try for alternate addressing mode if it encounters the restrictive addressing mode. But I am still getting the following error main1.c:11: error: insn does not satisfy its constraints: (insn 30 29 7 2 main1.c:9 (set (reg:QI 2 d2 [orig:61<variable>.a+1 ] [61]) (mem/s/j:QI (plus:SI (reg:SI 16 r0) (const_int 1 [0x1])) [0<variable>.a+1 S1 A8])) 41 {movqi} (nil)) main1.c:11: internal compiler error: in reload_cse_simplify_operands, at postreload.c:396This approach can't work. There has to be a combination of constraints to accept any and every combination of operands permitted by the predicates "nonimmediate_operand" and "general_operand". Since neither of these exclude base registers beside the SP, they make it through to recog which punts when it can't find a which_alternative set to use. In this case general_operand has allowed an operand of type (mem (plus (reg) (const)), equivalent to your Sb2 constraint, but there is no constraint for operand 1 that permits that. You can't use constraints to filter the initial selection performed by predicates. What I think you need to do is to have a variant version of general_operand that refuses Sb2 types.
This can be worked around with careful selection of operand predicates, secondary reloads, sometimes additional patterns. It's been a long time since I worked on a port with this kind of characteristic, so I can't offhand give a recipe to make it work.
Obviously looking at how other ports with these characteristics handle this case would be useful. The PA for example has integer indexed loads, but no integer indexed stores. There's likely other ports with similar characteristics as well.
Jeff
