feat: extract some function helpers

1 files changed, 108 insertions, 0 deletions

diff --git a/src/helpers/function.S b/src/helpers/function.S
new file mode 100644
index 0000000..c6647e9
--- /dev/null
+++ b/src/helpers/function.S
@@ -0,0 +1,108 @@
+.set _FUNCTION_IS_IN_FUNCTION_DEFINITION, 0
+.set _FUNCTION_LOCALS_ALLOCATED, 0
+
+.macro _function_local_variable scope, name, size
+  .if _FUNCTION_IS_IN_FUNCTION_DEFINITION == 0
+    .error "Cannot define a local variable outside of a function."
+  .else
+    .set _FRAME_OFFSET, _FRAME_OFFSET + \size
+    .equ \scope\()_name, -_FRAME_OFFSET
+  .endif
+.endm
+
+.macro _function_allocate_local_variables scope
+  .if _FUNCTION_IS_IN_FUNCTION_DEFINITION == 0
+    .error "Cannot allocate local variables outside of a function."
+  .elseif _FUNCTION_LOCALS_ALLOCATED == 1
+    .error "Local variables have already been allocated."
+  .else
+    .set _FUNCTION_LOCALS_ALLOCATED, 1
+    .equ \scope\()_FRAME_SIZE, (_FRAME_OFFSET + 15) & -16
+    .if \scope\()_FRAME_SIZE > 0
+      sub $\scope\()_FRAME_SIZE, %rsp
+    .endif
+  .endif
+.endm
+
+.macro _function_load_local scope, name, register
+  .if _FUNCTION_IS_IN_FUNCTION_DEFINITION == 0
+    .error "Cannot load a local variable outside of a function."
+  .elseif _FUNCTION_LOCALS_ALLOCATED == 0
+    .error "Local variables have not been allocated."
+  .else
+    mov \scope\()_name(%rbp), \register
+  .endif
+.endm
+
+.macro _function_store_local scope, register, name
+  .if _FUNCTION_IS_IN_FUNCTION_DEFINITION == 0
+    .error "Cannot store a local variable outside of a function."
+  .elseif _FUNCTION_LOCALS_ALLOCATED == 0
+    .error "Local variables have not been allocated."
+  .else
+    mov \register, \scope\()_name(%rbp)
+  .endif
+.endm
+
+.macro function_begin name
+  .if _FUNCTION_IS_IN_FUNCTION_DEFINITION == 1
+    .error "Cannot define a function inside of another function."
+  .endif
+
+  .set _FUNCTION_IS_IN_FUNCTION_DEFINITION, 1
+  .set _FUNCTION_LOCALS_ALLOCATED, 0
+
+  .macro define_local var_name, var_size
+    _function_local_variable \name, \var_name, \var_size
+  .endm
+
+  .macro allocate_locals
+    _function_allocate_local_variables \name
+  .endm
+
+  .macro load_local var_name, register
+    _function_load_local \name, \var_name, \register
+  .endm
+
+  .macro store_local register, var_name
+    _function_store_local \name, \register, \var_name
+  .endm
+
+  .macro function_exit
+    jmp .Lexit_\name
+  .endm
+
+  .macro function_end
+    .if _FRAME_OFFSET > 0
+      .if _FUNCTION_LOCALS_ALLOCATED == 0
+        .error "Local variables were never been allocated."
+      .endif
+    .endif
+
+    .Lexit_\name:
+      leave
+      .cfi_def_cfa %rsp, 8
+      ret
+      .cfi_endproc
+      .size \name, .-\name
+      .set _FUNCTION_IS_IN_FUNCTION_DEFINITION, 0
+      .set _FUNCTION_LOCALS_ALLOCATED, 0
+      .purgem allocate_locals
+      .purgem function_end
+      .purgem function_exit
+      .purgem load_local
+      .purgem define_local
+      .purgem store_local
+  .endm
+
+  .globl \name
+  .type \name, @function
+  \name:
+    .cfi_startproc
+    push %rbp
+    .cfi_def_cfa_offset 16
+    .cfi_offset %rbp, -16
+    mov %rsp, %rbp
+    .cfi_def_cfa_register %rbp
+    .set _FRAME_OFFSET, 0
+.endm