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Constraints and reload
- From: Jean Christophe Beyler <jean dot christophe dot beyler at gmail dot com>
- To: gcc at gcc dot gnu dot org
- Date: Mon, 14 Sep 2009 13:18:25 -0400
- Subject: Constraints and reload
I was working on simplifying the movdi in my port and I had put :
[(set (match_operand:DI 0 "nonimmediate_operand" "=r,r,r,o")
(match_operand:DI 1 "general_operand" "r,i,o,r"))]
However, due to constraints on the offset that is allowed, I:
- Added the check of the offset in the expand
- Added the check of the offset in the definition of the instruction
- Changed the constraints to:
[(set (match_operand:DI 0 "nonimmediate_operand" "=r,r,r,R")
(match_operand:DI 1 "general_operand" "r,i,R,r"))]
Where R checks if the operand is a memory operand and if the offset is correct.
Once I did that, in one case of my regression tests, I received the error:
asm operand requires impossible reload
However, if I generate what I get in the first version, all the moves
seem to be correct anyway.
My theory is that reload needs the o EVEN IF what it will be trying to
do is illegal and it will figure that out and finally generate the
right thing afterwards.
Thus, why the o is necessary and not the R.
Is this correct?
Jean Christophe Beyler