From edd8ff2c0778d97808869488cc7394151456c4ca Mon Sep 17 00:00:00 2001 From: Xiretza Date: Tue, 21 Apr 2020 12:51:58 +0200 Subject: Add flooring division operator The $div and $mod cells use truncating division semantics (rounding towards 0), as defined by e.g. Verilog. Another rounding mode, flooring (rounding towards negative infinity), can be used in e.g. VHDL. The new $divfloor cell provides this flooring division. This commit also fixes the handling of $div in opt_expr, which was previously optimized as if it was $divfloor. --- techlibs/common/simlib.v | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) (limited to 'techlibs/common/simlib.v') diff --git a/techlibs/common/simlib.v b/techlibs/common/simlib.v index 57fc07caa..125b8e013 100644 --- a/techlibs/common/simlib.v +++ b/techlibs/common/simlib.v @@ -997,6 +997,12 @@ endmodule // -------------------------------------------------------- +// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---| +//- +//- $div (A, B, Y) +//- +//- Division with truncated result (rounded towards 0). +//- module \$div (A, B, Y); parameter A_SIGNED = 0; @@ -1053,6 +1059,43 @@ endmodule // -------------------------------------------------------- +// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---| +//- +//- $divfloor (A, B, Y) +//- +//- Division with floored result (rounded towards negative infinity). +//- +module \$divfloor (A, B, Y); + +parameter A_SIGNED = 0; +parameter B_SIGNED = 0; +parameter A_WIDTH = 0; +parameter B_WIDTH = 0; +parameter Y_WIDTH = 0; + +input [A_WIDTH-1:0] A; +input [B_WIDTH-1:0] B; +output [Y_WIDTH-1:0] Y; + +generate + if (A_SIGNED && B_SIGNED) begin:BLOCK1 + localparam WIDTH = + A_WIDTH >= B_WIDTH && A_WIDTH >= Y_WIDTH ? A_WIDTH : + B_WIDTH >= A_WIDTH && B_WIDTH >= Y_WIDTH ? B_WIDTH : Y_WIDTH; + wire [WIDTH:0] A_buf, B_buf, N_buf; + assign A_buf = $signed(A); + assign B_buf = $signed(B); + assign N_buf = (A[A_WIDTH-1] == B[B_WIDTH-1]) || A == 0 ? A_buf : $signed(A_buf - (B[B_WIDTH-1] ? B_buf+1 : B_buf-1)); + assign Y = $signed(N_buf) / $signed(B_buf); + end else begin:BLOCK2 + assign Y = A / B; + end +endgenerate + +endmodule + +// -------------------------------------------------------- + // |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---| //- //- $modfloor (A, B, Y) -- cgit v1.2.3