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switch / case / default

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pommicket 2022-02-13 13:42:26 -05:00
parent 5dba28b8ba
commit 24f260fa16
2 changed files with 104 additions and 5 deletions
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95
05/codegen.b
View file

@ -1,3 +1,13 @@
; @TODO : declarations need to be done differently.
; this should work, but doesn't currently;
; goto lbl1;
; {
; int x;
; lbl1: ...
; }
; CALLING CONVENTION:
; Here is the process for calling a function:
; - the caller pushes the arguments on to the stack, from right to left
@ -26,6 +36,10 @@ global curr_function_return_type
global break_refs ; 0-terminated array of pointers to be filled in with the break offset
global continue_refs
; address of previous "case" label
global prev_case_addr
#define REG_RAX 0
#define REG_RBX 3
#define REG_RCX 1
@ -2586,6 +2600,9 @@ function generate_statement
if c == STATEMENT_BREAK goto gen_stmt_break
if c == STATEMENT_LABEL goto gen_stmt_label
if c == STATEMENT_GOTO goto gen_stmt_goto
if c == STATEMENT_SWITCH goto gen_stmt_switch
if c == STATEMENT_CASE goto gen_stmt_case
if c == STATEMENT_DEFAULT goto gen_stmt_default
; @TODO
die(.str_genstmtNI)
@ -2742,13 +2759,25 @@ function generate_statement
*4p = d
return
:gen_stmt_continue
if continue_refs == 0 goto continue_outside_of_loop
emit_jmp_rel32(0) ; jmp +0 (temporary)
add_ref(continue_refs, code_output)
return
:continue_outside_of_loop
statement_error(statement, .str_continue_outside_of_loop)
:str_continue_outside_of_loop
string continue statement not inside loop.
byte 0
:gen_stmt_break
if break_refs == 0 goto break_outside_of_loop
emit_jmp_rel32(0) ; jmp +0 (temporary)
add_ref(break_refs, code_output)
return
:break_outside_of_loop
statement_error(statement, .str_break_outside_of_loop)
:str_break_outside_of_loop
string break statement not inside loop or switch.
byte 0
:gen_stmt_label
if codegen_second_pass != 0 goto gen_label_pass2
ident_list_add(curr_function_labels, dat1, code_output)
@ -2778,6 +2807,72 @@ function generate_statement
:str_bad_label
string Unrecognized label.
byte 0
:gen_stmt_switch
break_refs = malloc(8000)
local old_prev_case_addr
old_prev_case_addr = prev_case_addr
generate_push_expression_casted(statement, dat1, TYPE_UNSIGNED_LONG)
emit_pop_rax() ; pop rax
emit_mov_reg(REG_RBX, REG_RAX) ; mov rbx, rax
emit_jmp_rel32(0) ; jmp +0 (temporary)
prev_case_addr = code_output
generate_statement(dat2)
addr1 = code_output
handle_refs(&break_refs, prev_break_refs, addr1)
; fill in last jump, if any
if prev_case_addr == 0 goto switch_had_default
d = addr1 - prev_case_addr
p = prev_case_addr - 4
*4p = d
:switch_had_default
prev_case_addr = old_prev_case_addr
return
:gen_stmt_case
if prev_case_addr == 0 goto gen_bad_case
emit_jmp_rel32(0) ; jump over the part where we deal with this case label
addr0 = code_output
; fill in previous jump
d = addr0 - prev_case_addr
p = prev_case_addr - 4
*4p = d
emit_mov_rax_imm64(dat1)
emit_cmp_rax_rbx()
emit_jne_rel32(0)
prev_case_addr = code_output
addr1 = code_output
; fill in jump over comparison
d = addr1 - addr0
p = addr0 - 4
*4p = d
return
:gen_bad_case
; @NONSTANDARD: we don't allow `case X:` after `default:`
; it's very annoying that the C standard allows that
statement_error(statement, .str_gen_bad_case)
:str_gen_bad_case
string Either case outside of switch, or case following default.
byte 0
:gen_stmt_default
addr0 = code_output
; fill in previous jump
d = addr0 - prev_case_addr
p = prev_case_addr - 4
*4p = d
prev_case_addr = 0
return
function generate_function
argument function_name
argument function_statement

14
05/main.c
View file

@ -28,10 +28,14 @@ int f() {
}
int main(int argc, char **argv) {
int exp = 0;
lb:
exp++;
if (exp < 10) goto lb;
return exp ;
int a = 5;
switch(a++){
case 5: a++;
case 3: a++;
case 4: a++;
default: a++;
}
return a ;
}