Github_Repos/cvw
1
0
Fork 1
mirror of https://github.com/openhwgroup/cvw synced 2025-02-11 06:05:49 +00:00
Code Issues Packages Projects Releases Wiki Activity

Cleaning shifter

Browse Source
This commit is contained in:
David Harris 2021-12-18 09:43:09 -08:00
parent ebcffcdebd
commit 53baf3e787
1 changed files with 3 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
wally-pipelined/src/ieu/shifter.sv
View File

@ -38,7 +38,7 @@ module shifter (
// extension. // extension.
generate generate
if (`XLEN==32) begin if (`XLEN==32) begin:shifter
// funnel shifter (see CMOS VLSI Design 4e Section 11.8.1, note Table 11.11 shift types wrong) // funnel shifter (see CMOS VLSI Design 4e Section 11.8.1, note Table 11.11 shift types wrong)
logic [62:0] z, zshift; logic [62:0] z, zshift;
logic [4:0] offset; logic [4:0] offset;
@ -56,7 +56,7 @@ module shifter (
// funnel operation // funnel operation
assign zshift = z >> offset; assign zshift = z >> offset;
assign y = zshift[31:0]; assign y = zshift[31:0];
end else begin // RV64 end else begin:shifter // RV64
// funnel shifter followed by masking // funnel shifter followed by masking
// research idea: investigate shifter designs for mixed 32/64-bit shifts // research idea: investigate shifter designs for mixed 32/64-bit shifts
logic [126:0] z, zshift; logic [126:0] z, zshift;
@ -83,12 +83,7 @@ module shifter (
// funnel operation // funnel operation
assign zshift = z >> offset; assign zshift = z >> offset;
assign ylower = zshift[31:0]; assign y = zshift[63:0];
// mask upper 32 bits for W-type 32-bit shifts
// harris: is there a clever way to get zshift[31] earlier for arithmetic right shifts to speed up critical path?
assign yupper = w64 ? {32{zshift[31]}} : zshift[63:32];
assign y = {yupper, ylower};
end end
endgenerate endgenerate
endmodule endmodule