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Merged
merged 7 commits into from
Sep 5, 2025
Merged

Improve SSA optimizations #268

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13f90a9
Add ARM BX instruction for function returns
jserv Sep 5, 2025
81fa621
Add constant folding for unary operators
jserv Sep 5, 2025
a06e3c6
Improve dead code elimination
jserv Sep 5, 2025
400ec54
Add safety guards for division and modulo optimizations
jserv Sep 5, 2025
9b42b28
Enhance algebraic simplifications
jserv Sep 5, 2025
474be1a
Add phi node optimization
jserv Sep 5, 2025
807f02f
Implement multi-instruction analysis and optimization
jserv Sep 5, 2025
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6 changes: 6 additions & 0 deletions src/arm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -329,6 +329,12 @@ int __blx(arm_cond_t cond, arm_reg rd)
return arm_encode(cond, 18, 15, 15, rd + 3888);
}

int __bx(arm_cond_t cond, arm_reg rm)
{
/* BX: Branch and Exchange */
return (cond << 28) | 0x012FFF10 | rm;
}

int __mul(arm_cond_t cond, arm_reg rd, arm_reg r1, arm_reg r2)
{
return arm_encode(cond, 0, rd, 0, (r1 << 8) + 144 + r2);
Expand Down
58 changes: 46 additions & 12 deletions src/parser.c
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Expand Up @@ -1750,18 +1750,40 @@ void read_expr_operand(block_t *parent, basic_block_t **bb)
read_expr_operand(parent, bb);

rs1 = opstack_pop();
vd = require_var(parent);
gen_name_to(vd->var_name);
opstack_push(vd);
add_insn(parent, *bb, OP_log_not, vd, rs1, NULL, 0, NULL);

/* Constant folding for logical NOT */
if (rs1 && rs1->is_const && !rs1->ptr_level && !rs1->is_global) {
vd = require_var(parent);
gen_name_to(vd->var_name);
vd->is_const = true;
vd->init_val = !rs1->init_val;
opstack_push(vd);
add_insn(parent, *bb, OP_load_constant, vd, NULL, NULL, 0, NULL);
} else {
vd = require_var(parent);
gen_name_to(vd->var_name);
opstack_push(vd);
add_insn(parent, *bb, OP_log_not, vd, rs1, NULL, 0, NULL);
}
Comment on lines +1755 to +1767
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require_var() and gen_name_to() can be moved to before the if statement to improve code reusability. That is:

vd = require_var(parent);
gen_name_to(vd->var_name);
if (rs1 && rs1->is_const && !rs1->ptr_level && !rs1->is_global) {
    vd->is_const = true;
    ...
} else {
    opstack_push(vd);
    add_insn(...);
}

} else if (lex_accept(T_bit_not)) {
read_expr_operand(parent, bb);

rs1 = opstack_pop();
vd = require_var(parent);
gen_name_to(vd->var_name);
opstack_push(vd);
add_insn(parent, *bb, OP_bit_not, vd, rs1, NULL, 0, NULL);

/* Constant folding for bitwise NOT */
if (rs1 && rs1->is_const && !rs1->ptr_level && !rs1->is_global) {
vd = require_var(parent);
gen_name_to(vd->var_name);
vd->is_const = true;
vd->init_val = ~rs1->init_val;
opstack_push(vd);
add_insn(parent, *bb, OP_load_constant, vd, NULL, NULL, 0, NULL);
} else {
vd = require_var(parent);
gen_name_to(vd->var_name);
opstack_push(vd);
add_insn(parent, *bb, OP_bit_not, vd, rs1, NULL, 0, NULL);
}
Comment on lines +1774 to +1786
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Ditto.

} else if (lex_accept(T_ampersand)) {
handle_address_of_operator(parent, bb);
} else if (lex_accept(T_asterisk)) {
Expand Down Expand Up @@ -2179,10 +2201,22 @@ void read_expr_operand(block_t *parent, basic_block_t **bb)

if (is_neg) {
rs1 = opstack_pop();
vd = require_var(parent);
gen_name_to(vd->var_name);
opstack_push(vd);
add_insn(parent, *bb, OP_negate, vd, rs1, NULL, 0, NULL);

/* Constant folding for negation */
if (rs1 && rs1->is_const && !rs1->ptr_level && !rs1->is_global) {
vd = require_var(parent);
gen_name_to(vd->var_name);
vd->is_const = true;
vd->init_val = -rs1->init_val;
opstack_push(vd);
add_insn(parent, *bb, OP_load_constant, vd, NULL, NULL, 0,
NULL);
} else {
vd = require_var(parent);
gen_name_to(vd->var_name);
opstack_push(vd);
add_insn(parent, *bb, OP_negate, vd, rs1, NULL, 0, NULL);
}
Comment on lines +2205 to +2219
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Ditto.

}
}
}
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