I am sorry that I am still confused about that.
Is this what you want ?
bool use_minus_p = TREE_CODE (step) == INTEGER_CST && ((TYPE_UNSIGNED
(TREE_TYPE (step)) && tree_int_cst_lt (step1, step))
|| (!TYPE_UNSIGNED (TREE_TYPE (step)) &&
!tree_expr_nonnegative_warnv_p (step, &ovf) && may_negate_without_overflow_p
(step)));
/* For easier readability of the created code, produce MINUS_EXPRs
when suitable. */
if (TREE_CODE (step) == INTEGER_CST)
{
if (TYPE_UNSIGNED (TREE_TYPE (step)))
{
step1 = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
if (tree_int_cst_lt (step1, step))
{
incr_op = MINUS_EXPR; /* Remove it. */
step = step1;
}
}
else
{
bool ovf;
if (!tree_expr_nonnegative_warnv_p (step, &ovf)
&& may_negate_without_overflow_p (step))
{
incr_op = MINUS_EXPR; /* Remove it. */
step = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
}
}
}
if (POINTER_TYPE_P (TREE_TYPE (base)))
{
if (TREE_CODE (base) == ADDR_EXPR)
mark_addressable (TREE_OPERAND (base, 0));
step = convert_to_ptrofftype (step);
if (incr_op == MINUS_EXPR) /* Change it into if (use_minus_p) */
step = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
incr_op = POINTER_PLUS_EXPR; /* Remove it. */
}
/* Gimplify the step if necessary. We put the computations in front of the
loop (i.e. the step should be loop invariant). */
step = force_gimple_operand (step, &stmts, true, NULL_TREE);
if (stmts)
gsi_insert_seq_on_edge_immediate (pe, stmts);
if (POINTER_TYPE_P (TREE_TYPE (base)))
stmt = gimple_build_assign (va, POINTER_PLUS_EXPR, vb, step);
else if (use_minus_p)
stmt = gimple_build_assign (va, MINUS_EXPR, vb, step);
else
stmt = gimple_build_assign (va, incr_op, vb, step);
...
Since I have no idea to make stmts flips between PLUS_EXPR and MINUS_EXPR.
Thanks.
[email protected]
From: Richard Sandiford
Date: 2023-05-11 05:28
To: 钟居哲
CC: gcc-patches; rguenther
Subject: Re: [PATCH V4] VECT: Add decrement IV iteration loop control by
variable amount support
钟居哲 <[email protected]> writes:
> Thanks Richard.
> I am planning to seperate a patch with only creat_iv stuff only.
>
> Are you suggesting that I remove "tree_code incr_op = code;"
> Use the argument directly ?
>
> I saw the codes here:
>
> /* For easier readability of the created code, produce MINUS_EXPRs
> when suitable. */
> if (TREE_CODE (step) == INTEGER_CST)
> {
> if (TYPE_UNSIGNED (TREE_TYPE (step)))
> {
> step1 = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
> if (tree_int_cst_lt (step1, step))
> {
> incr_op = MINUS_EXPR;
> step = step1;
> }
> }
> else
> {
> bool ovf;
>
> if (!tree_expr_nonnegative_warnv_p (step, &ovf)
> && may_negate_without_overflow_p (step))
> {
> incr_op = MINUS_EXPR;
> step = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
> }
> }
> }
> if (POINTER_TYPE_P (TREE_TYPE (base)))
> {
> if (TREE_CODE (base) == ADDR_EXPR)
> mark_addressable (TREE_OPERAND (base, 0));
> step = convert_to_ptrofftype (step);
> if (incr_op == MINUS_EXPR)
> step = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
> incr_op = POINTER_PLUS_EXPR;
> }
> /* Gimplify the step if necessary. We put the computations in front of the
> loop (i.e. the step should be loop invariant). */
> step = force_gimple_operand (step, &stmts, true, NULL_TREE);
> if (stmts)
> gsi_insert_seq_on_edge_immediate (pe, stmts);
>
> stmt = gimple_build_assign (va, incr_op, vb, step);
> ...
>
> It seems that it has complicated conditions here to change value of variable
> "incr_op".
> That's why I define a temporary variable "tree_code incr_op = code;" here and
> let the following codes change the value of "incr_op".
>
> Could you give me some hints of dealing with this piece of code to get rid of
> "tree_code incr_op = code;" ?
Yeah, but like I said in the review, those later:
incr_op = MINUS_EXPR;
stmts need to be updated to something that flips between PLUS_EXPR
and MINUS_EXPR (with updates to the comments). Just leaving them
as-is is incorrect (in cases where the caller passed MINUS_EXPR
rather than PLUS_EXPR).
The POINTER_PLUS_EXPR handling is fine due to the conditional
negate beforehand.
Thanks,
Richard
