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Fixed subword read to work with bigendian.

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This commit is contained in:
Ross Thompson 2022-09-15 13:59:01 -05:00
parent 877cc63063
commit 4c8ae8b421
2 changed files with 10 additions and 7 deletions
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2
pipelined/src/lsu/lsu.sv
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@ -328,7 +328,7 @@ module lsu (
// *** Ross Thompson: I think swr needs to be modified to support bigendian. Both the subword
// selected and the sign extension are probably wrong. I think it should be an invertion of
// the address bits and a different bit selected for extension.
subwordread subwordread(.ReadDataWordMuxM(LittleEndianReadDataWordM), .PAdrM(PAdrM[2:0]),
subwordread subwordread(.ReadDataWordMuxM(LittleEndianReadDataWordM), .PAdrM(PAdrM[2:0]), .BigEndianM,
.FpLoadStoreM, .Funct3M(LSUFunct3M), .ReadDataM);
subwordwrite subwordwrite(.LSUFunct3M, .IMAFWriteDataM, .LittleEndianWriteDataM);

15
pipelined/src/lsu/subwordread.sv
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@ -35,19 +35,22 @@ module subwordread
input logic [`LLEN-1:0] ReadDataWordMuxM,
input logic [2:0] PAdrM,
input logic [2:0] Funct3M,
input logic FpLoadStoreM,
input logic FpLoadStoreM,
input logic BigEndianM,
output logic [`LLEN-1:0] ReadDataM
);
logic [7:0] ByteM;
logic [15:0] HalfwordM;
logic [2:0] PAdrSwap;
// Funct3M[2] is the unsigned bit. mask upper bits.
// Funct3M[1:0] is the size of the memory access.
assign PAdrSwap = PAdrM ^ {3{BigEndianM}};
if (`XLEN == 64) begin:swrmux
// ByteMe mux
always_comb
case(PAdrM[2:0])
case(PAdrSwap[2:0])
3'b000: ByteM = ReadDataWordMuxM[7:0];
3'b001: ByteM = ReadDataWordMuxM[15:8];
3'b010: ByteM = ReadDataWordMuxM[23:16];
@ -60,7 +63,7 @@ module subwordread
// halfword mux
always_comb
case(PAdrM[2:1])
case(PAdrSwap[2:1])
2'b00: HalfwordM = ReadDataWordMuxM[15:0];
2'b01: HalfwordM = ReadDataWordMuxM[31:16];
2'b10: HalfwordM = ReadDataWordMuxM[47:32];
@ -70,7 +73,7 @@ module subwordread
logic [31:0] WordM;
always_comb
case(PAdrM[2])
case(PAdrSwap[2])
1'b0: WordM = ReadDataWordMuxM[31:0];
1'b1: WordM = ReadDataWordMuxM[63:32];
endcase
@ -103,7 +106,7 @@ module subwordread
end else begin:swrmux // 32-bit
// byte mux
always_comb
case(PAdrM[1:0])
case(PAdrSwap[1:0])
2'b00: ByteM = ReadDataWordMuxM[7:0];
2'b01: ByteM = ReadDataWordMuxM[15:8];
2'b10: ByteM = ReadDataWordMuxM[23:16];
@ -112,7 +115,7 @@ module subwordread
// halfword mux
always_comb
case(PAdrM[1])
case(PAdrSwap[1])
1'b0: HalfwordM = ReadDataWordMuxM[15:0];
1'b1: HalfwordM = ReadDataWordMuxM[31:16];
endcase