From: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
To: linux-sparse@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Bart Van Assche <bvanassche@acm.org>,
Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Subject: [PATCH 5/5] bitwise: early expansion of simple constants
Date: Mon, 27 Jun 2022 21:05:40 +0200 [thread overview]
Message-ID: <20220627190540.13358-6-luc.vanoostenryck@gmail.com> (raw)
In-Reply-To: <20220627190540.13358-1-luc.vanoostenryck@gmail.com>
C has only positive constants: -1 is really an expression,
the unary '-' operator applied to the constant 1. '-1' as
a constant value only exists after the expansion of constant
expressions.
This is rather unfortunate since it inhibits easy testing
of such constants in the evaluation phase, like here for
restricted_value().
So, expand expressions like +CTE, -CTE or ~CTE before
calling restricted_value().
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
---
evaluate.c | 48 +++++++++++++++++++++++++++++++++-
validation/bitwise-cast.c | 13 +++++++++
validation/bitwise-is-signed.c | 1 -
3 files changed, 60 insertions(+), 2 deletions(-)
diff --git a/evaluate.c b/evaluate.c
index bb8c0caa905a..33cc85c8d40f 100644
--- a/evaluate.c
+++ b/evaluate.c
@@ -413,11 +413,56 @@ static struct symbol *bad_expr_type(struct expression *expr)
return expr->ctype = &bad_ctype;
}
+static bool expand_simple_constant(struct expression *expr, struct symbol *type)
+{
+ unsigned long long val, mask;
+ struct expression *pre;
+ struct symbol *ctype;
+ unsigned size;
+
+ if (expr->type != EXPR_PREOP)
+ return false;
+ pre = expr->unop;
+ if (pre->type != EXPR_VALUE)
+ return false;
+
+ ctype = pre->ctype;
+ if (!ctype || ctype != type)
+ return false;
+
+ size = ctype->bit_size;
+ if (!size)
+ return false;
+
+ mask = sign_bit(size);
+ switch (expr->op) {
+ case '+':
+ val = pre->value;
+ break;
+ case '-':
+ val = pre->value;
+ if (val == mask && !(ctype->ctype.modifiers & MOD_UNSIGNED))
+ return false;
+ val = -val;
+ break;
+ case '~':
+ val = pre->value;
+ val = ~val;
+ break;
+ default:
+ return false;
+ }
+ expr->op = 0;
+ expr->type = EXPR_VALUE;
+ expr->value = val & bits_mask(size);
+ return true;
+}
+
static int restricted_value(struct expression *v, struct symbol *type)
{
if (v->type != EXPR_VALUE)
return 1;
- if (v->value != 0 && v->value != bits_mask(type->bit_size))
+ if (v->value != 0 && v->value != bits_mask(v->ctype->bit_size))
return 1;
return 0;
}
@@ -1919,6 +1964,7 @@ Normal:
if (!(class & TYPE_FLOAT)) {
ctype = integer_promotion(ctype);
expr->unop = cast_to(expr->unop, ctype);
+ expand_simple_constant(expr, ctype);
} else if (expr->op != '~') {
/* no conversions needed */
} else {
diff --git a/validation/bitwise-cast.c b/validation/bitwise-cast.c
index 1075a3e9410c..01af56c73751 100644
--- a/validation/bitwise-cast.c
+++ b/validation/bitwise-cast.c
@@ -48,6 +48,19 @@ static __be32 bar1(void)
return (__be32)0xffffffff;
}
+/* Implicit casts of minus one, legal */
+static __be32 foom(void)
+{
+ __be32 x = -1;
+ return x;
+}
+
+/* Explicit cast of minus one, legal */
+static __be32 barm(void)
+{
+ return (__be32)-1;
+}
+
/*
* check-name: conversions to bitwise types
* check-command: sparse -Wbitwise $file
diff --git a/validation/bitwise-is-signed.c b/validation/bitwise-is-signed.c
index dd9c147173cd..99d16bd20f9b 100644
--- a/validation/bitwise-is-signed.c
+++ b/validation/bitwise-is-signed.c
@@ -15,7 +15,6 @@ int fou(void) { return !is_signed_type(u); }
/*
* check-name: bitwise-is-signed
* check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
*
* check-output-ignore
* check-output-returns: 1
--
2.36.1
next prev parent reply other threads:[~2022-06-27 19:06 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220623180528.3595304-1-bvanassche@acm.org>
[not found] ` <20220623180528.3595304-52-bvanassche@acm.org>
[not found] ` <20220624045613.GA4505@lst.de>
[not found] ` <aa044f61-46f0-5f21-9b17-a1bb1ff9c471@acm.org>
[not found] ` <20220625092349.GA23530@lst.de>
[not found] ` <3eed7994-8de2-324d-c373-b6f4289a2734@acm.org>
2022-06-26 9:58 ` [PATCH 51/51] fs/zonefs: Fix sparse warnings in tracing code Luc Van Oostenryck
2022-06-26 15:42 ` Bart Van Assche
2022-06-26 16:24 ` Luc Van Oostenryck
2022-06-26 16:33 ` Linus Torvalds
2022-06-26 16:50 ` Linus Torvalds
2022-06-26 20:10 ` Luc Van Oostenryck
2022-06-26 19:44 ` Luc Van Oostenryck
2022-06-27 19:05 ` [PATCH 0/5] allow -1 and compares in bitwise types Luc Van Oostenryck
2022-06-27 19:05 ` [PATCH 1/5] bitwise: add testcases Luc Van Oostenryck
2022-06-27 19:05 ` [PATCH 2/5] bitwise: accept all ones as non-restricted value Luc Van Oostenryck
2022-06-27 23:32 ` Ramsay Jones
2022-06-27 19:05 ` [PATCH 3/5] bitwise: allow compares for bitwise types Luc Van Oostenryck
2022-06-27 19:20 ` Linus Torvalds
2022-06-27 23:34 ` Ramsay Jones
2022-06-27 19:05 ` [PATCH 4/5] bitwise: do not remove the signedness of " Luc Van Oostenryck
2022-06-27 19:05 ` Luc Van Oostenryck [this message]
2022-06-27 19:14 ` [PATCH 0/5] allow -1 and compares in " Linus Torvalds
2022-06-27 19:15 ` Bart Van Assche
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