impl x86_64 calling convention

5 files changed, 127 insertions, 11 deletions

diff --git a/codegen.c b/codegen.c
index 9d7f183..4e9f63a 100644
--- a/codegen.c
+++ b/codegen.c
@@ -1,6 +1,7 @@
 #include "ccc.h"
 #include "codegen.h"
 #include "scope.h"
+#include "register.h"
 #include <stdlib.h>
 #include <stdio.h>
 
@@ -14,17 +15,25 @@
 
 static const struct storage_location RV_LOC = {
     .type = REGISTER,
-    .label = "rax",
+    .reg = &RAX,
 };
+#define FULL_REG_SZ 8
 
 static struct scope* scope;
 
 static void emit_storage_loc(
     FILE* outfile,
-    const struct storage_location* loc
+    const struct storage_location* loc,
+    unsigned long long sz
 ) {
     switch (loc->type) {
         case REGISTER:
+            if (sz > 4) fprintf(outfile, "%s", loc->reg->qword);
+            else if (sz > 2) fprintf(outfile, "%s", loc->reg->dword);
+            // TODO: for word and byte make sure moving into these zeroes the high register
+            else if (sz > 1) fprintf(outfile, "%s", loc->reg->word);
+            else fprintf(outfile, "%s", loc->reg->byte);
+            break;
         case JMP_LABEL:
             fprintf(outfile, "%s", loc->label);
             break;
@@ -45,7 +54,7 @@ static void emit_int_lit(
 ) {
     if (storage != NULL) {
         fprintf(outfile, "\tmov ");
-        emit_storage_loc(outfile, storage);
+        emit_storage_loc(outfile, storage, FULL_REG_SZ);
         fprintf(outfile, ", %lld\n", node->val);
     }
 }
@@ -61,9 +70,9 @@ static void emit_var_ref(
             CGEN_PANIC("reference to undefined variable %s", node->ident);
 
         fprintf(outfile, "\tmov ");
-        emit_storage_loc(outfile, storage);
+        emit_storage_loc(outfile, storage, var_def.sz);
         fprintf(outfile, ", ");
-        emit_storage_loc(outfile, &var_def.loc);
+        emit_storage_loc(outfile, &var_def.loc, var_def.sz);
         fprintf(outfile, "\n");
     }
 }
@@ -108,6 +117,7 @@ static void emit_var_decl(FILE* outfile, const struct var_decl_node* node) {
             .type = BP_OFFSET,
             .offset = scope->bp_offset,
         },
+        .sz = type_sz,
     });
 }
 
@@ -137,10 +147,13 @@ static void emit_stmt_group(FILE* outfile, const struct group_node* node) {
         fprintf(outfile, "\tmov rsp, rbp\n");
     else {
         fprintf(outfile, "\tlea rsp, ");
-        emit_storage_loc(outfile, &(struct storage_location) {
-            .type = BP_OFFSET,
-            .offset = scope->bp_offset,
-        });
+        emit_storage_loc(
+            outfile,
+            &(struct storage_location) {
+                .type = BP_OFFSET,
+                .offset = scope->bp_offset,
+            },
+            FULL_REG_SZ);
         fprintf(outfile, "\n");
     }
 }
@@ -170,18 +183,41 @@ static void emit_fn_decl(FILE* outfile, const struct fn_decl_node* node) {
     scope_push(&scope);
     scope->bp_offset = 0;
 
+    long long spilled_bp_ofs = -16; // return address + old bp
+    unsigned long long arg_regnum = 0;
     struct var_decl_node* args_node = node->args_head;
     while (args_node != NULL) {
         unsigned long long type_sz = get_type_size(&args_node->type);
 
         scope->bp_offset += type_sz;
-        scope_define_var(scope, (struct var_def) {
+        struct var_def var_def = {
             .name = args_node->ident,
             .loc = {
                 .type = BP_OFFSET,
                 .offset = scope->bp_offset,
             },
-        });
+            .sz = type_sz,
+        };
+        scope_define_var(scope, var_def);
+
+        struct storage_location arg_src;
+        if (arg_regnum < CC_N_REGS) {
+            arg_src = (struct storage_location) {
+                .type = REGISTER,
+                .reg = CALLING_CONV[arg_regnum++]
+            };
+        } else {
+            arg_src = (struct storage_location) {
+                .type = BP_OFFSET,
+                .offset = spilled_bp_ofs,
+            };
+            spilled_bp_ofs -= type_sz;
+        }
+        fprintf(outfile, "\tmov ");
+        emit_storage_loc(outfile, &var_def.loc, type_sz);
+        fprintf(outfile, ", ");
+        emit_storage_loc(outfile, &arg_src,type_sz);
+        fprintf(outfile, "\n");
 
         args_node = args_node->next;
     }
diff --git a/register.c b/register.c
new file mode 100644
index 0000000..ca095ea
--- /dev/null
+++ b/register.c
@@ -0,0 +1,48 @@
+#include "register.h"
+
+const struct reg RAX = {
+    .qword = "rax",
+    .dword = "eax",
+    .word = "ax",
+    .byte = "al",
+};
+const struct reg RDI = {
+    .qword = "rdi",
+    .dword = "edi",
+    .word = "di",
+    .byte = "dil",
+};
+const struct reg RSI = {
+    .qword = "rsi",
+    .dword = "esi",
+    .word = "si",
+    .byte = "sil",
+};
+const struct reg RDX = {
+    .qword = "rdx",
+    .dword = "edx",
+    .word = "dx",
+    .byte = "dl",
+};
+const struct reg R10 = {
+    .qword = "r10",
+    .dword = "r10d",
+    .word = "r10w",
+    .byte = "r10b",
+};
+const struct reg R9 = {
+    .qword = "r9",
+    .dword = "r9d",
+    .word = "r9w",
+    .byte = "r9b",
+};
+const struct reg R8 = {
+    .qword = "r8",
+    .dword = "r8d",
+    .word = "r8w",
+    .byte = "r8b",
+};
+
+const struct reg* const CALLING_CONV[] = {&RDI, &RSI, &RDX, &R10, &R9, &R8};
+const unsigned long long CC_N_REGS =
+    sizeof(CALLING_CONV) / sizeof(const struct reg* const);
diff --git a/register.h b/register.h
new file mode 100644
index 0000000..323b668
--- /dev/null
+++ b/register.h
@@ -0,0 +1,22 @@
+#ifndef REGISTER_H
+#define REGISTER_H
+
+struct reg {
+    const char* qword;
+    const char* dword;
+    const char* word;
+    const char* byte;
+};
+
+extern const struct reg RAX;
+extern const struct reg RDI;
+extern const struct reg RSI;
+extern const struct reg RDX;
+extern const struct reg R10;
+extern const struct reg R9;
+extern const struct reg R8;
+
+extern const struct reg* const CALLING_CONV[];
+extern const unsigned long long CC_N_REGS;
+
+#endif
diff --git a/scope.h b/scope.h
index 36b6a93..e09e14e 100644
--- a/scope.h
+++ b/scope.h
@@ -10,7 +10,9 @@ struct storage_location {
     union {
         long long offset;
         const char* label;
+        const struct reg* reg;
     };
+    unsigned long long sz;
 };
 
 struct type_def {
@@ -21,6 +23,7 @@ struct type_def {
 struct var_def {
     const char* name;
     struct storage_location loc;
+    unsigned long long sz;
 };
 
 struct scope {
diff --git a/test/manyargs.c b/test/manyargs.c
new file mode 100644
index 0000000..28fbda4
--- /dev/null
+++ b/test/manyargs.c
@@ -0,0 +1,7 @@
+int get(int a, int b, int c, int d, int e, int f, int g) {
+    return g;
+}
+
+int main(int argc, char** argv) {
+    return get(argc, argc, argc, argc, argc, argc, argc);
+}