rvemu

commit 4e256a9cea6be3e08d06d1c63ab90e9cd4dd1824
parent 1b0c03d3ec03d206e74c17c7308f581f44332411
Author: Michail Konstantinos Dimopoulos <mk@mcdim.xyz>
Date:   Fri,  4 Sep 2026 00:14:56 +0300

Fixed imm sign bug and disasm bugs

Diffstat:
M
decode.h
 | 
26
+++++++++++++++++++++++---
M
disasm.c
 | 
10
++++------
M
main.c
 | 
22
+++++++++++++++-------

3 files changed, 42 insertions(+), 16 deletions(-)
diff --git a/decode.h b/decode.h
@@ -14,23 +14,43 @@ opcode	 0x33	 0000011  loads
 typedef struct {
 	uint8_t opcode;
 	uint8_t rd, rs1;
-	uint16_t imm;
+	//uint16_t imm;
+	int32_t imm;
 	uint8_t funct3;
 	uint8_t funct7, inimm;
 } itype_t;
 
-static inline void
+/*static inline void
 decode_itype(itype_t *i, uint32_t inst)
 {
 	i->rd =     (uint8_t)((inst >> 7) & 31);
 	i->funct3 = (uint8_t)((inst >> 12) & 7);
 	i->rs1 =    (uint8_t)((inst >> 15) & 31);
-	i->imm =    (uint16_t)((inst >> 20) & 2047);
+	//i->imm =    (uint16_t)((inst >> 20) & 2047);
+	i->imm =    (uint32_t)((inst >> 20) & 0xfff);
 
 	i->inimm =  (uint8_t)(i->imm & 31);
 	i->funct7 = (uint8_t)((i->imm >> 5) & 127);
+}*/
+static inline void
+decode_itype(itype_t *i, uint32_t inst)
+{
+    uint32_t raw_imm = (inst >> 20) & UINT32_C(0xfff);
+
+    i->rd     = (uint8_t)((inst >> 7) & UINT32_C(31));
+    i->funct3 = (uint8_t)((inst >> 12) & UINT32_C(7));
+    i->rs1    = (uint8_t)((inst >> 15) & UINT32_C(31));
+
+    i->inimm  = (uint8_t)(raw_imm & UINT32_C(31));
+    i->funct7 = (uint8_t)((inst >> 25) & UINT32_C(127));
+
+    i->imm = (int32_t)raw_imm;
+
+    if ((raw_imm & UINT32_C(0x800)) != 0u)
+        i->imm -= INT32_C(0x1000);
 }
 
+
 /*
 R-TYPE INSTRUCTION FORMAT
 31         25 24    20 19    15 14    12 11      7 6      0
diff --git a/disasm.c b/disasm.c
@@ -27,7 +27,7 @@ static void disasm_itype(uint32_t inst) {
 		printf("slti");
 		break;
 	case 0x3:
-		printf("sltui");
+		printf("sltiu");
 		break;
 	case 0x4:
 		printf("xori");
@@ -55,7 +55,7 @@ static void disasm_itype(uint32_t inst) {
 		printf("Illegal funct3\n");
 		return;
 	}
-	printf(" x%d, %" PRIu8 ", %" PRIu8 "\n", i.rd, i.rs1, i.imm);
+	printf(" x%d, %" PRIu8 ", %" PRId32 "\n", i.rd, i.rs1, i.imm);
 }
 
 static void disasm_rtype(uint32_t inst) {
@@ -139,7 +139,7 @@ static void disasm_itype_loads(uint32_t inst) {
 	}
 
 	printf(" x%" PRIu32 ", %" PRId32 "(x%" PRIu32 ")",
-	       i.rd, (int32_t)(int16_t)i.imm, i.rs1);
+	       i.rd, i.imm, i.rs1);
 }
 
 static void disasm_stype(uint32_t inst) {
@@ -209,7 +209,7 @@ static void disasm_itype_jalr(uint32_t inst) {
 	}
 	
 	printf("x%" PRIu32 ", %" PRId32 "(x%" PRIu32 ")\n",
-	       i.rd, (int32_t)(int16_t)i.imm, i.rs1);
+	       i.rd, i.imm, i.rs1);
 
 }
 
@@ -256,9 +256,7 @@ disasm_itype_control(uint32_t inst)
 	} else {
 		puts("Illegal instruction");
 		return;
-
 	}
-
 }
 
 static void
diff --git a/main.c b/main.c
@@ -96,9 +96,10 @@ static void exec_itype(cpu_state_t *cpu, uint32_t inst, uint8_t *mem) {
 	decode_itype(&i, inst);
 
 	uint32_t x; uint32_t shamt;
+	uint32_t uimm = (uint32_t)i.imm;
 	switch(i.funct3) {
 	case 0x0:
-		x = cpu->x[i.rs1]+i.imm;
+		x = cpu->x[i.rs1]+uimm;
 		break;
 	case 0x1:
 		if (i.funct7 == 0x00) {
@@ -113,19 +114,18 @@ static void exec_itype(cpu_state_t *cpu, uint32_t inst, uint8_t *mem) {
 		x = ((int32_t)cpu->x[i.rs1] < (int32_t)i.imm) ? 1 : 0;
 		break;
 	case 0x3:
-		x = (cpu->x[i.rs1] < i.imm) ? 1 : 0;
+		x = (cpu->x[i.rs1] < uimm) ? 1 : 0;
 		break;
 	case 0x4:
-		x = cpu->x[i.rs1]^i.imm;
+		x = cpu->x[i.rs1]^uimm;
 		break;
 	case 0x5:
+		shamt = i.imm & 31;
 		switch(i.funct7) {
 		case 0x00:
-			shamt = i.imm & 31;
 			x = cpu->x[i.rs1] >> shamt;
 			break;
 		case 0x20:
-			shamt = i.imm & 31;
 			x = (uint32_t)((int32_t)cpu->x[i.rs1] >> shamt);
 			break;
 		default:
@@ -134,10 +134,10 @@ static void exec_itype(cpu_state_t *cpu, uint32_t inst, uint8_t *mem) {
 		}
 		break;
 	case 0x6:
-		x = cpu->x[i.rs1]|i.imm;
+		x = cpu->x[i.rs1]|uimm;
 		break;
 	case 0x7:
-		x = cpu->x[i.rs1]&i.imm;
+		x = cpu->x[i.rs1]&uimm;
 		break;
 	default:
 		raise_trap(cpu, TRAP_ILLEGAL_INSTRUCTION, inst);
@@ -481,6 +481,7 @@ load_program(uint8_t *mem)
 {
 	/* PROGRAM */
 	uint32_t arr[] = {
+/*
 		0x00500193,	// addi x3, x0, 5
 		0x00600093,	// addi x1, x0, 6
 		0xaaaaa3b7,	// lui x7, 0xaaaaa		-> rd:aaaaa000
@@ -488,6 +489,13 @@ load_program(uint8_t *mem)
 		0x00000013,	// nop
 		0x0ff0000f,	// fence
 		0x00100073,	// ebreak
+*/
+	0xfff00093,  // addi  x1, x0, -1
+	0xfff04113,  // xori  x2, x0, -1
+	0xfff06193,  // ori   x3, x0, -1
+	0xfff17213,  // andi  x4, x2, -1
+	0xfff02293,  // slti  x5, x0, -1
+	0xfff03313   // sltiu x6, x0, -1
 	};
 	size_t len = sizeof(arr) / sizeof(arr[0]);