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-rw-r--r--qtmips_machine/core.cpp22
-rw-r--r--qtmips_machine/core.h1
2 files changed, 17 insertions, 6 deletions
diff --git a/qtmips_machine/core.cpp b/qtmips_machine/core.cpp
index a2cc74b..5768d9c 100644
--- a/qtmips_machine/core.cpp
+++ b/qtmips_machine/core.cpp
@@ -10,6 +10,7 @@ using namespace machine;
#define DM_ALUSRC (1L<<3)
#define DM_REGD (1L<<4)
#define DM_REGWRITE (1L<<5)
+#define DM_ZERO_EXTEND (1L<<6)
struct DecodeMap {
long flags;
@@ -22,6 +23,7 @@ struct DecodeMap {
#define NOPE { .flags = 0, NOALU, NOMEM }
#define FLAGS_ALU_I (DM_SUPPORTED | DM_ALUSRC | DM_REGWRITE)
+#define FLAGS_ALU_I_ZE (DM_SUPPORTED | DM_ALUSRC | DM_REGWRITE | DM_ZERO_EXTEND)
// This is map from opcode to signals.
static const struct DecodeMap dmap[] = {
@@ -37,9 +39,9 @@ static const struct DecodeMap dmap[] = {
{ .flags = FLAGS_ALU_I, .alu = ALU_OP_ADDU, NOMEM }, // ADDIU
{ .flags = FLAGS_ALU_I, .alu = ALU_OP_SLT, NOMEM }, // SLTI
{ .flags = FLAGS_ALU_I, .alu = ALU_OP_SLTU, NOMEM }, // SLTIU
- { .flags = FLAGS_ALU_I, .alu = ALU_OP_AND, NOMEM }, // ANDI
- { .flags = FLAGS_ALU_I, .alu = ALU_OP_OR, NOMEM }, // ORI
- { .flags = FLAGS_ALU_I, .alu = ALU_OP_XOR, NOMEM }, // XORI
+ { .flags = FLAGS_ALU_I_ZE, .alu = ALU_OP_AND, NOMEM }, // ANDI
+ { .flags = FLAGS_ALU_I_ZE, .alu = ALU_OP_OR, NOMEM }, // ORI
+ { .flags = FLAGS_ALU_I_ZE, .alu = ALU_OP_XOR, NOMEM }, // XORI
{ .flags = FLAGS_ALU_I, .alu = ALU_OP_LUI, NOMEM}, // LUI
NOPE, // 16
NOPE, // 17
@@ -128,11 +130,17 @@ struct Core::dtDecode Core::decode(const struct dtFetch &dt) {
std::uint32_t val_rs = regs->read_gp(dt.inst.rs());
std::uint32_t val_rt = regs->read_gp(dt.inst.rt());
+ std::uint32_t immediate_val;
+
+ if (dec.flags & DM_ZERO_EXTEND)
+ immediate_val = dt.inst.immediate();
+ else
+ immediate_val = sign_extend(dt.inst.immediate());
emit decode_instruction_value(dt.inst.data());
emit decode_reg1_value(val_rs);
emit decode_reg2_value(val_rt);
- emit decode_immediate_value(sign_extend(dt.inst.immediate()));
+ emit decode_immediate_value(immediate_val);
emit decode_regw_value((bool)(dec.flags & DM_REGWRITE));
emit decode_memtoreg_value((bool)(dec.flags & DM_MEMREAD));
emit decode_memwrite_value((bool)(dec.flags & DM_MEMWRITE));
@@ -151,6 +159,7 @@ struct Core::dtDecode Core::decode(const struct dtFetch &dt) {
.memctl = dec.mem_ctl,
.val_rs = val_rs,
.val_rt = val_rt,
+ .immediate_val = immediate_val,
.ff_rs = FORWARD_NONE,
.ff_rt = FORWARD_NONE,
};
@@ -166,7 +175,7 @@ struct Core::dtExecute Core::execute(const struct dtDecode &dt) {
std::uint32_t alu_sec = dt.val_rt;
if (dt.alusrc)
- alu_sec = sign_extend(dt.inst.immediate()); // Sign extend to 32bit
+ alu_sec = dt.immediate_val; // Sign or zero extend immediate value
std::uint32_t alu_val = alu_operate(dt.aluop, dt.val_rs, alu_sec, dt.inst.shamt(), regs);
@@ -175,7 +184,7 @@ struct Core::dtExecute Core::execute(const struct dtDecode &dt) {
emit execute_reg2_value(dt.val_rt);
emit execute_reg1_ff_value(dt.ff_rs);
emit execute_reg2_ff_value(dt.ff_rt);
- emit execute_immediate_value(sign_extend(dt.inst.immediate()));
+ emit execute_immediate_value(dt.immediate_val);
emit execute_regw_value(dt.regwrite);
emit execute_memtoreg_value(dt.memread);
emit execute_memread_value(dt.memread);
@@ -298,6 +307,7 @@ void Core::dtDecodeInit(struct dtDecode &dt) {
dt.aluop = ALU_OP_SLL;
dt.val_rs = 0;
dt.val_rt = 0;
+ dt.immediate_val = 0;
dt.ff_rs = FORWARD_NONE;
dt.ff_rt = FORWARD_NONE;
}
diff --git a/qtmips_machine/core.h b/qtmips_machine/core.h
index 386b486..0c9a1b1 100644
--- a/qtmips_machine/core.h
+++ b/qtmips_machine/core.h
@@ -89,6 +89,7 @@ protected:
enum MemoryAccess::AccessControl memctl; // Decoded memory access type
std::uint32_t val_rs; // Value from register rs
std::uint32_t val_rt; // Value from register rt
+ std::uint32_t immediate_val; // zero or sign-extended immediate value
ForwardFrom ff_rs;
ForwardFrom ff_rt;
};