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added a little code for elimination of unneeded code generated

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This commit is contained in:
hyunghwan.chung 2017-01-29 07:29:58 +00:00
parent 03ddf6b68d
commit 341966e373
2 changed files with 42 additions and 4 deletions
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9
moo/kernel/Mill.moo
View File

@ -183,6 +183,15 @@ class MyObject(Object)
if (a > 20) { break }.
a dump.
}.
nil.
1.
0.
self.
thisProcess.
thisContext.
nil.
nil.
'---------- END ------------' dump.
##Processor sleepFor: 20.
}

37
moo/lib/comp.c
View File

@ -4841,7 +4841,7 @@ static int compile_special_statement (moo_t* moo)
return emit_backward_jump_instruction (moo, moo->c->mth.code.len - moo->c->mth.loop->startpos);
}
return 9999;
return 9999; /* to indicate that no special stament has been seen and processed */
}
static int compile_block_statement (moo_t* moo)
@ -4870,7 +4870,6 @@ static int compile_method_statement (moo_t* moo)
if (n == 9999)
{
/* TODO: optimization. if expresssion is a literal, no push and pop are required */
/* the second parameter to compile_method_expression() indicates
* that the stack top will eventually be popped off. the compiler
* can optimize some instruction sequencese. for example, two
@ -4879,13 +4878,43 @@ static int compile_method_statement (moo_t* moo)
* the compile_method_expression() function emits POP_INTO_XXX
* instructions if the second parameter is 1 whenever possible and
* STORE_INTO_XXX if it's 0.*/
moo_oow_t preexprpos;
preexprpos = moo->c->mth.code.len;
n = compile_method_expression(moo, 1);
if (n <= -1) return -1;
/* if n is 1, no stack popping is required */
/* if n is 1, no stack popping is required as POP_INTO_XXX has been
* emitted in place of STORE_INTO_XXX. */
if (n == 0)
{
return emit_byte_instruction (moo, BCODE_POP_STACKTOP);
if (preexprpos + 1 == moo->c->mth.code.len)
{
/* TODO: MORE optimization. if expresssion is a literal, no push and pop are required. check for multie-byte instructions as well */
switch (moo->c->mth.code.ptr[preexprpos])
{
case BCODE_PUSH_NIL:
case BCODE_PUSH_TRUE:
case BCODE_PUSH_FALSE:
case BCODE_PUSH_CONTEXT:
case BCODE_PUSH_PROCESS:
case BCODE_PUSH_NEGONE:
case BCODE_PUSH_ZERO:
case BCODE_PUSH_ONE:
case BCODE_PUSH_TWO:
/* eliminate the unneeded push instruction */
n = 0;
moo->c->mth.code.len = preexprpos;
break;
default:
goto pop_stacktop;
}
}
else
{
pop_stacktop:
return emit_byte_instruction (moo, BCODE_POP_STACKTOP);
}
}
}