Problem with ALU54D, "Unable to find legal placement" about nextpnr HOT 5 CLOSED

Well, you're right - this chip has 5 DSP blocks, two macros in each. Five mult36x36 seems to pick them all.

mult36x36 is made up of 4 mult18x18, the results of which are compressed and added together using alu54d, which are in these dsps, so the usage report is somewhat lying.

from nextpnr.

I think it is a bit hard to understand, but does it mean we only have 5x ALU54 and 5x MULT36x36.
So if we use all 5x MULT36x36, they use the 5x ALU54, to add their results?

from nextpnr.

Here is one macro: two mult18x18 and alu54d

two macros form one DSP block.

Mult36x36 splits the input operands into 18-bit chunks and multiplies each chunk by each.
The results of the multiplications are then shifted and summed to produce a 72-bit result. Four 18x18 multipliers are used for multiplying chunks, and two ALU54Ds are used for shifting and subsequent summing.

Thus, using one Mult36x36 you occupy 4 mult18x18 and two ALU54d

If necessary, I can draw a picture of multiplication and shifts along each wire, although it will be a large picture.

from nextpnr.

Ahh I see! Now it makes sense. Just got it trough using all 10 ALU54, by reducing some of the MULT36.

Thank you for the help!
Just a note, but maybe you could change the "Device utilisation:" to whenever a MULT36 is used, it should add +2 on the ALU54, maybe in parentheses.

Info: Device utilisation:
Info: 	                 VCC:     1/    1   100%
Info: 	                 IOB:    25/  274     9%
Info: 	                LUT4:  2396/ 8640    27%
Info: 	              OSER16:     0/   80     0%
Info: 	              IDES16:     0/   80     0%
Info: 	            IOLOGICI:     0/  276     0%
Info: 	            IOLOGICO:     0/  276     0%
Info: 	           MUX2_LUT5:   390/ 4320     9%
Info: 	           MUX2_LUT6:    94/ 2160     4%
Info: 	           MUX2_LUT7:    35/ 1080     3%
Info: 	           MUX2_LUT8:    14/ 1080     1%
Info: 	                 ALU:   722/ 6480    11%
Info: 	                 GND:     1/    1   100%
Info: 	                 DFF:  1819/ 6480    28%
Info: 	           RAM16SDP4:     0/  270     0%
Info: 	               BSRAM:     7/   26    26%
Info: 	              ALU54D:     4(10)/   10    40%       edit
Info: 	     MULTADDALU18X18:     0/   10     0%
Info: 	        MULTALU18X18:     0/   10     0%
Info: 	        MULTALU36X18:     0/   10     0%
Info: 	           MULT36X36:     3/    5    60%
Info: 	           MULT18X18:     0/   20     0%
Info: 	             MULT9X9:     0/   40     0%
Info: 	              PADD18:     0/   20     0%
Info: 	               PADD9:     0/   40     0%
Info: 	                 GSR:     1/    1   100%
Info: 	                 OSC:     0/    1     0%
Info: 	                rPLL:     1/    2    50%
Info: 	                BUFG:     0/   22     0%

from nextpnr.

yes that would be nice, I haven’t delved into it yet because this part is not specific to Gowin and is located somewhere at the upper general levels :)

from nextpnr.