From 58ffe8a7dbf57d5637e091083175028eb9614636 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Tue, 2 Nov 2021 16:55:17 +0100
Subject: Add numerical comparison operations (binary only)

---
 src/compiler.h | 68 +++++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 58 insertions(+), 10 deletions(-)

diff --git a/src/compiler.h b/src/compiler.h
index a40fb1e..b703a99 100644
--- a/src/compiler.h
+++ b/src/compiler.h
@@ -79,7 +79,7 @@ typedef enum OpType {
     OP_GREATER,
     OP_LESS,
     OP_GREATER_EQ,
-    OP_LESS_EQL,
+    OP_LESS_EQ,
 } OpType;
 
 void
@@ -112,10 +112,6 @@ compile_type_predicate(OpType op, Object* args) {
     printf("    ;; <-- compile_type_predicate\n");
 }
 
-
-// TODO: Next -> numerical comparison operators
-// "=", "<", ">", "<=", ">=",
-
 void
 compile_logic_list(OpType op, Object* args) {
     printf("    ;; --> compile_logic_list\n");
@@ -162,6 +158,58 @@ compile_logic_list(OpType op, Object* args) {
     printf("    ;; <-- compile_logic_list\n");
 }
 
+void
+compile_cmp_list(OpType op, Object* args) {
+    printf("    ;; --> compile_cmp_list\n");
+    compile_object(args->head);
+
+    // TODO: Make sure to stop evaluating if the condition is not met.
+    // FIXME: Only working for two argument lists right now because we can't
+    // accumulate the bool and compare it with an int. We can fix it by passing
+    // two values on the stack (previous value and current result) or by only
+    // passing a previous value and having a conditional jump (need labels for
+    // that).
+    args = args->tail;
+    while (args != NULL) {
+        compile_object(args->head);
+        args = args->tail;
+
+        // Current value.
+        printf("    pop     rcx\n");
+        printf("    sar     rcx, %d\n", FIXNUM_SHIFT);
+
+        // Previous value.
+        printf("    pop     rax\n");
+        printf("    sar     rax, %d\n", FIXNUM_SHIFT);
+
+        printf("    cmp     rax, rcx\n");
+        printf("    mov     rax, 0\n");
+
+        switch (op) {
+            case OP_EQUAL: {
+                printf("    sete    al\n");
+            } break;
+            case OP_GREATER: {
+                printf("    setg    al\n");
+            } break;
+            case OP_LESS: {
+                printf("    setl    al\n");
+            } break;
+            case OP_GREATER_EQ: {
+                printf("    setge   al\n");
+            } break;
+            case OP_LESS_EQ: {
+                printf("    setle   al\n");
+            } break;
+            default: break;
+        }
+        printf("    shl     rax, %d\n", BOOL_SHIFT);
+        printf("    or      rax, %d\n", BOOL_TAG);
+        printf("    push    rax\n");
+    }
+    printf("    ;; <-- compile_cmp_list\n");
+}
+
 void
 compile_arithmetic_list(OpType op, Object* args) {
     printf("    ;; --> compile_arithmetic\n");
@@ -236,15 +284,15 @@ compile_proc_call(Object *obj) {
     } else if (sv_equal(&obj->head->text, &STRING("or"))) {
         compile_logic_list(OP_OR, obj->tail);
     } else if (sv_equal(&obj->head->text, &STRING("="))) {
-        compile_logic_list(OP_EQUAL, obj->tail);
+        compile_cmp_list(OP_EQUAL, obj->tail);
     } else if (sv_equal(&obj->head->text, &STRING(">"))) {
-        compile_logic_list(OP_GREATER, obj->tail);
+        compile_cmp_list(OP_GREATER, obj->tail);
     } else if (sv_equal(&obj->head->text, &STRING("<"))) {
-        compile_logic_list(OP_LESS, obj->tail);
+        compile_cmp_list(OP_LESS, obj->tail);
     } else if (sv_equal(&obj->head->text, &STRING(">="))) {
-        compile_logic_list(OP_GREATER_EQ, obj->tail);
+        compile_cmp_list(OP_GREATER_EQ, obj->tail);
     } else if (sv_equal(&obj->head->text, &STRING("<="))) {
-        compile_logic_list(OP_LESS_EQL, obj->tail);
+        compile_cmp_list(OP_LESS_EQ, obj->tail);
     } else {
         fprintf(stderr, "error: not implemented\n");
         exit(EXIT_FAILURE);
-- 
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