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🐛 Fix decoding bug in compressed shifts

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This commit is contained in:
Florian Zaruba 2017-07-13 12:33:39 +02:00
parent 390b3dbef4
commit c000d60eab
1 changed files with 5 additions and 4 deletions
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9
src/compressed_decoder.sv
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@ -127,8 +127,9 @@ module compressed_decoder
2'b01: begin
// 00: c.srli -> srli rd, rd, shamt
// 01: c.srai -> srai rd, rd, shamt
instr_o = {1'b0, instr_i[10], 5'b0, instr_i[6:2], 2'b01, instr_i[9:7], 3'b101, 2'b01, instr_i[9:7], OPCODE_OPIMM};
if (instr_i[6:2] == 5'b0) illegal_instr_o = 1'b1;
instr_o = {1'b0, instr_i[10], 4'b0, instr_i[12], instr_i[6:2], 2'b01, instr_i[9:7], 3'b101, 2'b01, instr_i[9:7], OPCODE_OPIMM};
// shamt field must be non-zero
if ({instr_i[12], instr_i[6:2]} == 6'b0) illegal_instr_o = 1'b1;
end
2'b10: begin
@ -192,9 +193,9 @@ module compressed_decoder
unique case (instr_i[15:13])
3'b000: begin
// c.slli -> slli rd, rd, shamt
instr_o = {7'b0, instr_i[6:2], instr_i[11:7], 3'b001, instr_i[11:7], OPCODE_OPIMM};
instr_o = {6'b0, instr_i[12], instr_i[6:2], instr_i[11:7], 3'b001, instr_i[11:7], OPCODE_OPIMM};
if (instr_i[11:7] == 5'b0) illegal_instr_o = 1'b1; // register not x0
if (instr_i[6:2] == 5'b0) illegal_instr_o = 1'b1; // shift amount must be non zero
if ({instr_i[12], instr_i[6:2]} == 6'b0) illegal_instr_o = 1'b1; // shift amount must be non zero
end
3'b010: begin