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Short-circuiting Boolean "and" and "or" operators.

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Stephen Dolan committed 2012-09-04 20:38:59 +01:00
1 parent c5ab3b2336
commit 6e6ea50763
5 files changed
+62 -5
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c/compile.c
+40 -5
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@@ -348,14 +348,49 @@ block gen_definedor(block a, block b) {
return c;
}
static block gen_condbranch(block iftrue, block iffalse) {
block b = gen_noop();
block_append(&iftrue, gen_op_target(JUMP, iffalse));
block_append(&b, gen_op_target(JUMP_F, iftrue));
block_append(&b, iftrue);
block_append(&b, iffalse);
return b;
}
block gen_and(block a, block b) {
// a and b = if a then (if b then true else false) else false
block code = gen_op_simple(DUP);
block_append(&code, a);
block if_a_true = gen_op_simple(POP);
block_append(&if_a_true, b);
block_append(&if_a_true, gen_condbranch(gen_op_const(LOADK, jv_true()),
gen_op_const(LOADK, jv_false())));
block_append(&code, gen_condbranch(if_a_true,
block_join(gen_op_simple(POP), gen_op_const(LOADK, jv_false()))));
return code;
}
block gen_or(block a, block b) {
// a or b = if a then true else (if b then true else false)
block code = gen_op_simple(DUP);
block_append(&code, a);
block if_a_false = gen_op_simple(POP);
block_append(&if_a_false, b);
block_append(&if_a_false, gen_condbranch(gen_op_const(LOADK, jv_true()),
gen_op_const(LOADK, jv_false())));
block_append(&code, gen_condbranch(block_join(gen_op_simple(POP), gen_op_const(LOADK, jv_true())),
if_a_false));
return code;
}
block gen_cond(block cond, block iftrue, block iffalse) {
block b = gen_op_simple(DUP);
block_append(&b, cond);
block_append(&iftrue, gen_op_target(JUMP, iffalse));
block_append(&b, gen_op_target(JUMP_F, iftrue));
block_append(&b, block_join(gen_op_simple(POP), iftrue));
block_append(&b, block_join(gen_op_simple(POP), iffalse));
block_append(&b, gen_condbranch(block_join(gen_op_simple(POP), iftrue),
block_join(gen_op_simple(POP), iffalse)));
return b;
}