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Initial support for decoding Capability Memory instructions.

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This commit is contained in:
jon
2020-05-05 12:23:10 +01:00
parent 21d1207e6b
commit 500811430b
1 changed files with 95 additions and 4 deletions
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99
src_Core/RISCY_OOO/procs/lib/Decode.bsv
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@@ -156,6 +156,84 @@ function Maybe#(MemInst) decodeMemInst(Instruction inst);
end
endfunction
function Maybe#(MemInst) decodeCapMemInst(Instruction inst);
// This function trusts that its result will only be used by
// explicit capability instructions as identified by the primary
// decode case, and therefore does not attempt to return sensible
// defaults when the instruction is not a capability memory operation.
Bool illegalInst = False;
Bit#(7) funct7 = inst[31:25];
Bit#(5) mem_code = (funct7==f7_cap_Loads) ? inst[24:20]:inst[11:7];
Bool amo = unpack(mem_code[4]);
Bool ddc = !unpack(mem_code[3]);
Bool unsind = unpack(mem_code[2]);
Bit#(2) width = mem_code[1:0];
Bool capWidth = (funct7 == f7_cap_Stores && unsind && width == 0);
if (funct7 == f7_cap_Loads && amo && width == 3) begin
capWidth = True;
amo = False;
end
// mem_func + amo_func
MemFunc mem_func = Ld;
AmoFunc amo_func = None;
if (funct7 == f7_cap_Loads) begin
mem_func = (amo) ? Lr:Ld;
end else if (funct7 == f7_cap_Stores) begin
mem_func = (amo) ? Sc:St;
end
// unsignedLd
// it doesn't matter if this is set to True for stores
Bool unsignedLd = unsind;
// byteEn
// TODO: Some combinations of operations and byteEn's are illegal.
// They should be detected here.
MemDataByteEn byteEn = (capWidth) ? replicate(True):replicate(False);
if (!capWidth) begin
case (width)
0 : byteEn[0] = True;
1 : begin
byteEn[0] = True;
byteEn[1] = True;
end
2 : begin
byteEn[0] = True;
byteEn[1] = True;
byteEn[2] = True;
byteEn[3] = True;
end
3 : begin
byteEn[0] = True;
byteEn[1] = True;
byteEn[2] = True;
byteEn[3] = True;
byteEn[4] = True;
byteEn[5] = True;
byteEn[6] = True;
byteEn[7] = True;
end
endcase
end
Bool aq = False;
Bool rl = False;
if (illegalInst) begin
return tagged Invalid;
end else begin
return tagged Valid ( MemInst{
mem_func: mem_func,
amo_func: amo_func,
unsignedLd: unsignedLd,
byteEn: byteEn,
aq: aq,
rl: rl } );
end
endfunction
(* noinline *)
function DecodeResult decode(Instruction inst);
RiscVISASubset isa = defaultValue;
@@ -203,6 +281,7 @@ function DecodeResult decode(Instruction inst);
// Results of mini-decoders
Maybe#(MemInst) mem_inst = decodeMemInst(inst);
Maybe#(MemInst) cap_mem_inst = decodeCapMemInst(inst);
// TODO better detection of illegal insts
case (opcode)
@@ -1053,12 +1132,24 @@ function DecodeResult decode(Instruction inst);
dInst.execFunc = CapModify (BuildCap);
end
f7_cap_Loads: begin
illegalInst = True;
//TODO
dInst.iType = Ld;
if (cap_mem_inst matches tagged Valid .ci) dInst.execFunc = tagged Mem ci;
else illegalInst = True;
regs.dst = Valid(tagged Gpr rd);
regs.src1 = Valid(tagged Gpr rs1);
regs.src2 = Invalid;
dInst.imm = Valid (0);
dInst.csr = tagged Invalid;
end
f7_cap_Stores: begin
illegalInst = True;
//TODO
dInst.iType = St;
if (cap_mem_inst matches tagged Valid .ci) dInst.execFunc = tagged Mem ci;
else illegalInst = True;
regs.dst = Invalid;
regs.src1 = Valid(tagged Gpr rs1);
regs.src2 = Valid(tagged Gpr rs2);
dInst.imm = Valid (0);
dInst.csr = tagged Invalid;
end
f7_cap_TwoOp: begin
case (funct5rs2)