From e18b172d3e4e31b4d50ca978a66187730f744a31 Mon Sep 17 00:00:00 2001
From: Mathias Magnusson <mathias@magnusson.space>
Date: Mon, 2 Jun 2025 21:13:42 +0200
Subject: add read_int built in procedure

---
 src/codegen.zig | 111 +++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 77 insertions(+), 34 deletions(-)

(limited to 'src/codegen.zig')

diff --git a/src/codegen.zig b/src/codegen.zig
index 07f3a4d..d2b5d2a 100644
--- a/src/codegen.zig
+++ b/src/codegen.zig
@@ -610,40 +610,83 @@ const Context = struct {
         }
     }
 
-    fn genPrint(self: *Context, print: compile.Instr.Print) !void {
-        const num = self.register_allocator.get(print.arg);
-
-        const quot = try self.register_allocator.allocateAux();
-        defer self.register_allocator.freeAux(quot);
-        const digit = try self.register_allocator.allocateAux();
-        defer self.register_allocator.freeAux(digit);
-        const count = try self.register_allocator.allocate(print.dest);
-
-        try self.maybeFreeSources();
-
-        try self.emit(.addi(digit, .zero, '\n'));
-        try self.emit(.addi(.sp, .sp, -1));
-        try self.emit(.sb(.sp, 0, digit));
-        try self.emit(.addi(count, .zero, 1));
-        try self.emit(.addi(quot, .zero, 10));
-
-        try self.emit(.addi(digit, num, 0));
-        try self.emit(.divu(num, digit, quot));
-        try self.emit(.remu(digit, digit, quot));
-        try self.emit(.addi(digit, digit, '0'));
-        try self.emit(.addi(.sp, .sp, -1));
-        try self.emit(.sb(.sp, 0, digit));
-        try self.emit(.addi(count, count, 1));
-        try self.emit(.bne(num, .zero, -4 * 7));
-
-        try self.emit(.addi(.a7, .zero, 64)); // no = write
-        try self.emit(.addi(.a0, .zero, 1)); // fd = stdout
-        try self.emit(.addi(.a1, .sp, 0)); // buf = sp
-        try self.emit(.addi(.a2, count, 0)); // count = count
-        try self.emit(.ecall()); // syscall(no, fd, buf, count)
-        try self.emit(.add(.sp, .sp, count));
-
-        try self.emit(.addi(count, count, -1));
+    fn genProcCall(self: *Context, call: compile.Instr.ProcCall) !void {
+        switch (call.proc) {
+            .print => {
+                const num = self.register_allocator.get(call.arg);
+
+                const quot = try self.register_allocator.allocateAux();
+                defer self.register_allocator.freeAux(quot);
+                const digit = try self.register_allocator.allocateAux();
+                defer self.register_allocator.freeAux(digit);
+                const count = try self.register_allocator.allocate(call.dest);
+
+                try self.maybeFreeSources();
+
+                try self.emit(.addi(digit, .zero, '\n'));
+                try self.emit(.addi(.sp, .sp, -1));
+                try self.emit(.sb(.sp, 0, digit));
+                try self.emit(.addi(count, .zero, 1));
+                try self.emit(.addi(quot, .zero, 10));
+
+                try self.emit(.addi(digit, num, 0));
+                try self.emit(.divu(num, digit, quot));
+                try self.emit(.remu(digit, digit, quot));
+                try self.emit(.addi(digit, digit, '0'));
+                try self.emit(.addi(.sp, .sp, -1));
+                try self.emit(.sb(.sp, 0, digit));
+                try self.emit(.addi(count, count, 1));
+                try self.emit(.bne(num, .zero, -4 * 7));
+
+                try self.emit(.addi(.a7, .zero, @intFromEnum(std.os.linux.syscalls.RiscV64.write)));
+                try self.emit(.addi(.a0, .zero, 1)); // fd = stdout
+                try self.emit(.addi(.a1, .sp, 0)); // buf = sp
+                try self.emit(.addi(.a2, count, 0)); // count = count
+                try self.emit(.ecall()); // syscall(no, fd, buf, count)
+                try self.emit(.add(.sp, .sp, count));
+
+                try self.emit(.addi(count, count, -1));
+            },
+            .read_int => {
+                try self.maybeFreeSources();
+
+                const result = try self.register_allocator.allocate(call.dest);
+                const ptr = try self.register_allocator.allocateAux();
+                defer self.register_allocator.freeAux(ptr);
+                const char = try self.register_allocator.allocateAux();
+                defer self.register_allocator.freeAux(char);
+                const newline = try self.register_allocator.allocateAux();
+                defer self.register_allocator.freeAux(newline);
+
+                try self.emit(.addi(.sp, .sp, -21));
+                try self.emit(.addi(newline, .zero, '\n'));
+                try self.emit(.addi(result, .zero, 0));
+
+                try self.emit(.addi(.a7, .zero, @intFromEnum(std.os.linux.syscalls.RiscV64.read)));
+                try self.emit(.addi(.a0, .zero, 0)); // fd = stdin
+                try self.emit(.addi(.a1, .sp, 0)); // buf = sp
+                try self.emit(.addi(.a2, .zero, 21)); // count = count
+                try self.emit(.ecall()); // syscall(no, fd, buf, count)
+
+                try self.emit(.addi(ptr, .sp, 0));
+                try self.emit(.add(.a0, .a0, .sp)); // a0 = end
+
+                // loop start
+                try self.emit(.bgeu(ptr, .a0, 4 * 8)); // done
+                try self.emit(.lb(char, ptr, 0));
+                try self.emit(.beq(char, newline, 4 * 6)); // done
+                try self.emit(.mul(result, result, newline)); // '\n' happens to also be 10
+                try self.emit(.addi(char, char, -'0'));
+                // assert 0 <= char <= 9
+                try self.emit(.add(result, result, char));
+
+                try self.emit(.addi(ptr, ptr, 1));
+                try self.emit(.jal(.zero, -4 * 7)); // -> loop start
+                // done
+
+                try self.emit(.addi(.sp, .sp, 21));
+            },
+        }
     }
 
     fn genDiscard(self: *Context, _: compile.Instr.Discard) !void {
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