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Re: Help math RTL patterns...
- From: Nathan Sidwell <nathan at acm dot org>
- To: Steve Silva <stv_007 at yahoo dot com>, "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Date: Tue, 17 Jan 2017 14:45:10 -0500
- Subject: Re: Help math RTL patterns...
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On 01/17/2017 12:19 PM, Steve Silva via gcc wrote:
I am porting gcc for an internal processor and I am having some issues with math instructions. Our processor uses two operands for math instructions which are usually of the form OP0 = OP0 + OP1. The RTL pattern (for addm3) in gcc uses the form OP0 = OP1 + OP2. I understand that gcc supposedly supports the two operand flavor, but I have not been able to convince it to do that for me. I tried the following RTL pattern with no success:
So I used the three operand form and fixed things up in the code:
That's nearly right.
Use register constraints with the 3 op pattern:
[(set (match_operand:HI 0 "register_operand" "+a")
(plus:HI (match_operand:HI 1 "register_operand" "0")
(match_operand:HI 2 "general_operand" "aim")))]
The sh port may be instructive, IIRC it has a bunch of 2-op insns.