ADD: update files

main.S

@@ -4,63 +4,37 @@
 	.attribute unaligned_access, 0
 	.attribute stack_align, 16
 	.text
+	.globl	GPIO_PIN
+	.section	.srodata,"a"
+	.align	2
+	.type	GPIO_PIN, @object
+	.size	GPIO_PIN, 4
+GPIO_PIN:
+	.word	1
+	.globl	counter
+	.section	.sbss,"aw",@nobits
+	.align	2
+	.type	counter, @object
+	.size	counter, 4
+counter:
+	.zero	4
+	.text
 	.align	1
-	.type	simpleDelay, @function
-simpleDelay:
-	addi	sp,sp,-32
-	sd	s0,24(sp)
-	addi	s0,sp,32
-	sw	zero,-20(s0)
-	j	.L2
-.L3:
- #APP
-# 16 "./main.c" 1
+	.globl	delay
+	.type	delay, @function
+delay:
+	addi	sp,sp,-48
+	sd	s0,40(sp)
+	addi	s0,sp,48
+	mv	a5,a0
+	sw	a5,-36(s0)
 	nop
-# 0 "" 2
- #NO_APP
-	lw	a5,-20(s0)
-	addiw	a5,a5,1
-	sw	a5,-20(s0)
 .L2:
-	lw	a5,-20(s0)
-	sext.w	a4,a5
-	li	a5,999424
-	addi	a5,a5,575
-	ble	a4,a5,.L3
-	nop
-	nop
-	ld	s0,24(sp)
-	addi	sp,sp,32
-	jr	ra
-	.size	simpleDelay, .-simpleDelay
-	.align	1
-	.globl	main
-	.type	main, @function
-main:
-	addi	sp,sp,-16
-	sd	ra,8(sp)
-	sd	s0,0(sp)
-	addi	s0,sp,16
-	li	a5,268500992
-	li	a4,1
-	sw	a4,0(a5)
-.L5:
-	li	a5,268500992
+	li	a5,33603584
+	addi	a5,a5,-8
 	lw	a5,0(a5)
 	sext.w	a4,a5
-	li	a5,268500992
-	ori	a4,a4,1
-	sext.w	a4,a4
-	sw	a4,0(a5)
-	call	simpleDelay
-	li	a5,268500992
-	lw	a5,0(a5)
-	sext.w	a4,a5
-	li	a5,268500992
-	andi	a4,a4,-2
-	sext.w	a4,a4
-	sw	a4,0(a5)
-	call	simpleDelay
-	j	.L5
-	.size	main, .-main
-	.ident	"GCC: (SiFive GCC-Metal 10.2.0-2020.12.8) 10.2.0"
+	lw	a5,-20(s0)
+	subw	a5,a4,a5
+# ...
+# more contents omitted

main.c

@@ -1,30 +1,42 @@
-#define SET_BITS(REG, BIT)            ((REG) |= (BIT))
-#define CLEAR_BITS(REG, BIT)          ((REG) &= ~(BIT))
+// some handy macros to do bit operations
+#define SET_BITS(REG, BIT)              ((REG) |= (BIT))
+#define CLEAR_BITS(REG, BIT)            ((REG) &= !(BIT))
 
-#define GPIOA_BASE                    0x10010000U
+// peripheral MMIO addresses
+#define GPIOA_OUTPUT_VAL                0x1001000CUL
+#define GPIOA_OUTPUT_EN                 0x10010008UL
+#define CLINT_MTIME                     0x0200BFF8UL
 
-#define GPIO_PIN_0                    0b0001U
-#define GPIO_PIN_1                    0b0001U
-#define GPIO_PIN_2                    0b0001U
-#define GPIO_PIN_3                    0b0001U
+// the pin we are using
+const unsigned int GPIO_PIN = 0x01;
 
+// a global counter
+volatile unsigned int counter;
 
-
-
-static inline void simpleDelay() {
-  for (int i=0; i<1000000; i+=1) {
-    __asm__("nop");
-  }
+// A simple delay function. 
+void delay(unsigned int ticks) {
+  unsigned int mtime_start;
+  while ((*(volatile unsigned int *)CLINT_MTIME) - mtime_start < ticks) {}
 }
 
-int main() {
-  *(unsigned int volatile *)(GPIOA_BASE + 0x00U) = GPIO_PIN_0;
+void main() {
+  // enable GPIOA as output
+  SET_BITS(*(volatile unsigned int *)GPIOA_OUTPUT_EN, GPIO_PIN);
 
   while (1) {
-    SET_BITS(*(unsigned int volatile *)(GPIOA_BASE + 0x00U), GPIO_PIN_0);
-    simpleDelay();
+    // if counter is even, turn on the LED, otherwise turn it off
+    if (counter % 2 == 0) {
+      SET_BITS(*(volatile unsigned int *)GPIOA_OUTPUT_VAL, GPIO_PIN);
+    } else {
+      CLEAR_BITS(*(volatile unsigned int *)GPIOA_OUTPUT_VAL, GPIO_PIN);
+    }
+
+    // delay for 1 second
+    delay(1000);
 
-    CLEAR_BITS(*(unsigned int volatile *)(GPIOA_BASE + 0x00U), GPIO_PIN_0);
-    simpleDelay();
+    // increment the counter
+    counter += 1;
   }
-}
+
+  // we won't reach here if everything is working
+}

main.i

@@ -2,21 +2,36 @@
 # 1 "<built-in>"
 # 1 "<command-line>"
 # 1 "./main.c"
-# 14 "./main.c"
-static inline void simpleDelay() {
-  for (int i=0; i<1000000; i+=1) {
-    __asm__("nop");
-  }
+# 11 "./main.c"
+const unsigned int GPIO_PIN = 0x01;
+
+
+volatile unsigned int counter;
+
+
+void delay(unsigned int ticks) {
+  unsigned int mtime_start;
+  while ((*(volatile unsigned int *)0x0200BFF8UL) - mtime_start < ticks) {}
 }
 
-int main() {
-  *(unsigned int volatile *)(0x10010000U + 0x00U) = 0b0001U;
+void main() {
+
+  ((*(volatile unsigned int *)0x10010008UL) |= (GPIO_PIN));
 
   while (1) {
-    ((*(unsigned int volatile *)(0x10010000U + 0x00U)) |= (0b0001U));
-    simpleDelay();
 
-    ((*(unsigned int volatile *)(0x10010000U + 0x00U)) &= ~(0b0001U));
-    simpleDelay();
+    if (counter % 2 == 0) {
+      ((*(volatile unsigned int *)0x1001000CUL) |= (GPIO_PIN));
+    } else {
+      ((*(volatile unsigned int *)0x1001000CUL) &= !(GPIO_PIN));
+    }
+
+
+    delay(1000);
+
+
+    counter += 1;
   }
-}
+
+
+}