release C1 lecture

commit 0b17b38a5ba9e69472695ba2e6715c7659c4cbbb
Author: Julie Zelenski <[email protected]>
Date:   Sun Jan 12 23:16:32 2025 -0800

    release C1 lecture

Author: zelenski

_data/unreleased.csv

@@ -17,7 +17,6 @@ permalink,title,released
 "/labs/projectlab2/","Lab 9: Project Team Meeting 2",false
 "/lectures/Arithmetic/","Number Representation and Arithmetic",false
 "/lectures/Ben/","Magic of Computer Systems",false
-"/lectures/C_Control/","From Assembly to C",false
 "/lectures/C_Functions/","C Functions",false
 "/lectures/C_Mastery/","C Mastery",false
 "/lectures/C_Pointers/","C Pointers and Arrays",false

lectures/C_Control/README.md

@@ -0,0 +1,12 @@
+---
+released: true
+permalink: /lectures/C_Control/
+title: From Assembly to C
+readings: |
+    + Our [one-page guide to RISC-V](/guides/riscv-onepage).
+    + Brush up on C basics (syntax, data types, operators, control structures) via your favorite C reference; sections 1-2 of Nick Parlante's [EssentialC](http://cslibrary.stanford.edu/101/EssentialC.pdf); or chapters 1, 2, and 3 of K&R. Skip content on I/O and standard libraries (we are bare metal!)
+    + Read Dennis Ritchie's account of the [history of C](https://www.bell-labs.com/usr/dmr/www/chist.html)
+    + Try out the [Compiler Explorer](https://godbolt.org) demoed in lecture
+    + Read our guides on [make](/guides/make) and [gcc](/guides/gcc)
+---
+

lectures/C_Control/code/explorer.txt

@@ -0,0 +1,39 @@
+// Some C examples to try out 
+// in Compiler Explorer https://godbolt.org
+
+int main(void)
+{
+    unsigned int val = 0x3a;
+    int count = 0;
+
+    while (val != 0) {
+        if (val & 1) count++;
+        val = val >> 1;
+    }
+    return count;
+}
+
+int binky(int arg)
+{
+    int result = arg + 13;
+    result = result * arg;
+    return result;
+}
+
+int winky(int arg)
+{
+    if (arg == 0)
+        arg++;
+    else
+        arg--;
+    return arg;
+}
+
+int pinky(int arg)
+{
+    int result = 1;
+    for (int i = 0; i < arg; i++)
+        result *= i;
+    return result;
+}
+

lectures/C_Control/code/freestanding/Makefile

@@ -0,0 +1,36 @@
+# This simple Makefile defines pattern rule to build 
+# name.bin from name.c C source file
+
+ARCH = -march=rv64im -mabi=lp64
+CFLAGS 	= $(ARCH) -g -Og -Wall -ffreestanding
+LDFLAGS = $(ARCH) -nostdlib -e main
+LDLIBS =
+
+all: dice dice.bin
+
+%.bin: %.elf
+	riscv64-unknown-elf-objcopy $*.elf -O binary $@
+
+%.elf: %.o
+	riscv64-unknown-elf-gcc $(LDFLAGS) $^ $(LDLIBS) -o $@
+
+%.o: %.c
+	riscv64-unknown-elf-gcc $(CFLAGS) -c $< -o $@
+
+%.o: %.s
+	riscv64-unknown-elf-as $< -o $@
+
+run: dice.bin
+	mango-run $<
+
+list: dice.o dice
+	riscv64-unknown-elf-objdump --no-show-raw-insn -d dice.o > dice.list
+	otool -v -t dice > dice.mac.list
+
+# This recipe is for a native executable on hosted environment
+# (not cross-compiled, not freestanding)
+%: %.c
+	clang -g -Wall $< -o $@
+
+clean: 
+	rm -rf *.list *.bin *.elf *.o dice a.out *.dSYM dice

lectures/C_Control/code/freestanding/dice.c

@@ -0,0 +1,19 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <time.h>
+
+const int NSIDES = 6;
+
+int main(int argc, char *argv[])
+{
+    int nrolls = 0;
+
+    srand(time(0));
+    while (1) {
+        nrolls++;
+        int val = rand() % NSIDES;
+        if (val == 4) break;
+    }
+    printf("It took %d tries to roll a four.\n", nrolls);
+    return nrolls;
+}

lectures/C_Control/code/makefiles/blink/Makefile

@@ -0,0 +1,12 @@
+# This very simple Makefile builds blink.bin
+# using fixed recipes
+
+blink.bin: blink.s
+	riscv64-unknown-elf-as blink.s -o blink.o
+	riscv64-unknown-elf-objcopy blink.o -O binary blink.bin
+
+run: blink.bin
+	mango-run blink.bin
+
+clean:
+	rm -f blink.o blink.bin

lectures/C_Control/code/makefiles/blink/blink.s

@@ -0,0 +1,15 @@
+# File blink.s
+# ------------
+# blink LED connected to GPIO PB0
+
+    lui     a0,0x2000
+    addi    a1,zero,1
+    sw      a1,0x30(a0)     # config PB0 as output pin
+loop:
+    xori    a1,a1,1         # xor ^ 1 invert bit 0
+    sw      a1,0x40(a0)     # update data register will flip on<->off
+    lui     a2,0x3f00
+delay:                      # busy loop to wait for a while
+    addi    a2,a2,-1
+    bne     a2,zero,delay
+    j loop                  # repeat forever

lectures/C_Control/code/makefiles/count/Makefile

@@ -0,0 +1,34 @@
+# This sample Makefile build a program for the Pi
+# from a single C source file
+# NAME.c => NAME.o => NAME.elf => NAME.bin
+# The recipes use pattern rules that allow you to
+# easily change the basename of the file to customize
+
+NAME = count
+
+ARCH    = -march=rv64im -mabi=lp64
+CFLAGS 	= $(ARCH) -g -Og -Wall -ffreestanding
+LDFLAGS = $(ARCH) -nostdlib -e main
+OBJDUMP_FLAGS = --no-show-raw-insn --no-addresses --disassembler-color=terminal --visualize-jumps
+
+all : $(NAME).bin
+
+%.bin: %.elf
+	riscv64-unknown-elf-objcopy $< -O binary $@
+
+%.elf: %.o
+	riscv64-unknown-elf-gcc $(LDFLAGS) $< -o $@
+
+%.o: %.c
+	riscv64-unknown-elf-gcc $(CFLAGS) -c $< -o $@
+
+list: $(NAME).o
+	riscv64-unknown-elf-objdump $(OBJDUMP_FLAGS) -d $<
+
+clean:
+	rm -f *.bin *.elf *.o *.list
+
+run: $(NAME).bin
+	mango-run $<
+
+.PHONY: all clean run list

lectures/C_Control/code/makefiles/count/count.c

@@ -0,0 +1,11 @@
+// Program to count the "on" bits in argument
+
+int main(unsigned arg)
+{
+    int count = 0;
+    do {
+        count += arg & 1;
+        arg >>= 1;
+    } while (arg);
+    return count;
+}