From 1eb41aeb49a491f5b18d160074e651a76afc655a Mon Sep 17 00:00:00 2001
From: Martin Jambor <mjambor@suse.cz>
Date: Tue, 17 Dec 2024 11:17:14 +0100
Subject: [PATCH] ipa: Better value ranges for pointer integer constants
When looking into cases where we know an actual argument of a call is
a constant but we don't generate a singleton value-range for the jump
function, I found out that the special handling of pointer constants
does not work well for constant zero pointer values. In fact the code
only attempts to see if it can figure out that an argument is not zero
and if it can figure out any alignment information.
With this patch, we try to use the value_range that ranger can give us
in the jump function if we can and we query ranger for all kinds of
arguments, not just SSA_NAMES (and so also pointer integer constants).
If we cannot figure out a useful range we fall back again on figuring
out non-NULLness with tree_single_nonzero_warnv_p.
With this patch, we generate
[prange] struct S * [0, 0] MASK 0x0 VALUE 0x0
instead of for example:
[prange] struct S * [0, +INF] MASK 0xfffffffffffffff0 VALUE 0x0
for a zero constant passed in a call.
If you are wondering why we check whether the value range obtained
from range_of_expr can be undefined, even when the function returns
true, that is because that can apparently happen fro default-definition
SSA_NAMEs.
gcc/ChangeLog:
2024-11-15 Martin Jambor <mjambor@suse.cz>
* ipa-prop.cc (ipa_compute_jump_functions_for_edge): Try harder to
use the value range obtained from ranger for pointer values.
---
gcc/ipa-prop.cc | 35 ++++++++++++++++-------------------
1 file changed, 16 insertions(+), 19 deletions(-)
diff --git a/gcc/ipa-prop.cc b/gcc/ipa-prop.cc
index ae309ec78a2d..f0b915ba2be1 100644
--- a/gcc/ipa-prop.cc
+++ b/gcc/ipa-prop.cc
@@ -2396,28 +2396,27 @@ ipa_compute_jump_functions_for_edge (struct ipa_func_body_info *fbi,
value_range vr (TREE_TYPE (arg));
if (POINTER_TYPE_P (TREE_TYPE (arg)))
{
- bool addr_nonzero = false;
- bool strict_overflow = false;
-
- if (TREE_CODE (arg) == SSA_NAME
- && param_type
- && get_range_query (cfun)->range_of_expr (vr, arg, cs->call_stmt)
- && vr.nonzero_p ())
- addr_nonzero = true;
- else if (tree_single_nonzero_warnv_p (arg, &strict_overflow))
- addr_nonzero = true;
-
- if (addr_nonzero)
- vr.set_nonzero (TREE_TYPE (arg));
-
+ if (!get_range_query (cfun)->range_of_expr (vr, arg, cs->call_stmt)
+ || vr.varying_p ()
+ || vr.undefined_p ())
+ {
+ bool strict_overflow = false;
+ if (tree_single_nonzero_warnv_p (arg, &strict_overflow))
+ vr.set_nonzero (TREE_TYPE (arg));
+ else
+ vr.set_varying (TREE_TYPE (arg));
+ }
+ gcc_assert (!vr.undefined_p ());
unsigned HOST_WIDE_INT bitpos;
- unsigned align, prec = TYPE_PRECISION (TREE_TYPE (arg));
+ unsigned align = BITS_PER_UNIT;
- get_pointer_alignment_1 (arg, &align, &bitpos);
+ if (!vr.singleton_p ())
+ get_pointer_alignment_1 (arg, &align, &bitpos);
if (align > BITS_PER_UNIT
&& opt_for_fn (cs->caller->decl, flag_ipa_bit_cp))
{
+ unsigned prec = TYPE_PRECISION (TREE_TYPE (arg));
wide_int mask
= wi::bit_and_not (wi::mask (prec, false, prec),
wide_int::from (align / BITS_PER_UNIT - 1,
@@ -2425,12 +2424,10 @@ ipa_compute_jump_functions_for_edge (struct ipa_func_body_info *fbi,
wide_int value = wide_int::from (bitpos / BITS_PER_UNIT, prec,
UNSIGNED);
irange_bitmask bm (value, mask);
- if (!addr_nonzero)
- vr.set_varying (TREE_TYPE (arg));
vr.update_bitmask (bm);
ipa_set_jfunc_vr (jfunc, vr);
}
- else if (addr_nonzero)
+ else if (!vr.varying_p ())
ipa_set_jfunc_vr (jfunc, vr);
else
gcc_assert (!jfunc->m_vr);
--
GitLab