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| author | Eddie Hung <eddie@fpgeh.com> | 2020-01-16 15:25:49 -0800 |
|---|---|---|
| committer | Eddie Hung <eddie@fpgeh.com> | 2020-01-21 15:19:41 -0800 |
| commit | 7977574995baa2cdba1401233179f9f84fe96a3a (patch) | |
| tree | 1649fe008d42e3b9be19aec510b6266da8749c32 /techlibs/common | |
| parent | f165a748244b022b215631ade2c8a5e0139cec09 (diff) | |
| download | yosys-7977574995baa2cdba1401233179f9f84fe96a3a.tar.gz yosys-7977574995baa2cdba1401233179f9f84fe96a3a.tar.bz2 yosys-7977574995baa2cdba1401233179f9f84fe96a3a.zip | |
New techmap +/shiftx2mux.v which decomposes LSB first; better for ABC
Diffstat (limited to 'techlibs/common')
| -rw-r--r-- | techlibs/common/Makefile.inc | 1 | ||||
| -rw-r--r-- | techlibs/common/shiftx2mux.v | 38 |
2 files changed, 39 insertions, 0 deletions
diff --git a/techlibs/common/Makefile.inc b/techlibs/common/Makefile.inc index a42f63128..5d797ec1d 100644 --- a/techlibs/common/Makefile.inc +++ b/techlibs/common/Makefile.inc @@ -30,3 +30,4 @@ $(eval $(call add_share_file,share,techlibs/common/cmp2lut.v)) $(eval $(call add_share_file,share,techlibs/common/cells.lib)) $(eval $(call add_share_file,share,techlibs/common/mul2dsp.v)) $(eval $(call add_share_file,share,techlibs/common/dummy.box)) +$(eval $(call add_share_file,share,techlibs/common/shiftx2mux.v)) diff --git a/techlibs/common/shiftx2mux.v b/techlibs/common/shiftx2mux.v new file mode 100644 index 000000000..5366d6749 --- /dev/null +++ b/techlibs/common/shiftx2mux.v @@ -0,0 +1,38 @@ +(* techmap_celltype = /*"$shift*/ "$shiftx" *) +module _80_shift_shiftx (A, B, Y); + parameter A_SIGNED = 0; + parameter B_SIGNED = 0; + parameter A_WIDTH = 1; + parameter B_WIDTH = 1; + parameter Y_WIDTH = 1; + + input [A_WIDTH-1:0] A; + input [B_WIDTH-1:0] B; + output [Y_WIDTH-1:0] Y; + + parameter [B_WIDTH-1:0] _TECHMAP_CONSTMSK_B_ = 0; + parameter [B_WIDTH-1:0] _TECHMAP_CONSTVAL_B_ = 0; + + generate + genvar i; + localparam CLOG2_Y_WIDTH = $clog2(Y_WIDTH); + + if (B_WIDTH <= CLOG2_Y_WIDTH+1) + wire _TECHMAP_FAIL_ = 1; + // In order to perform this optimisation, this $shiftx must + // only shift in units of Y_WIDTH, which we check by ensuring + // that the appropriate LSBs of B are zero + else if (_TECHMAP_CONSTMSK_B_[CLOG2_Y_WIDTH-1:0] == {CLOG2_Y_WIDTH{1'b1}} && _TECHMAP_CONSTVAL_B_[CLOG2_Y_WIDTH-1:0] != {CLOG2_Y_WIDTH{1'b0}}) + wire _TECHMAP_FAIL_ = 1; + else begin + // Halve the size of $shiftx by $mux-ing A according to + // the LSB of B, after discarding the zeroed bits + wire [(A_WIDTH+Y_WIDTH)/2-1:0] AA; + for (i = 0; i < (A_WIDTH/Y_WIDTH); i=i+2) + assign AA[(i/2)*Y_WIDTH +: Y_WIDTH] = B[CLOG2_Y_WIDTH] ? A[(i+1)*Y_WIDTH +: Y_WIDTH] : A[(i+0)*Y_WIDTH +: Y_WIDTH]; + $shiftx #(.A_SIGNED(A_SIGNED), .B_SIGNED(B_SIGNED), .A_WIDTH((A_WIDTH+Y_WIDTH)/2'd2), .B_WIDTH(B_WIDTH-1), .Y_WIDTH(Y_WIDTH)) _TECHMAP_REPLACE_ (.A(AA), .B({B[B_WIDTH-1:CLOG2_Y_WIDTH+1], {CLOG2_Y_WIDTH{1'b0}}}), .Y(Y)); + end + endgenerate +endmodule + + |