In perl.git, the branch blead has been updated
<https://perl5.git.perl.org/perl.git/commitdiff/ad9b9a4926e4b0d348c048937df69e382f7e6d27?hp=59592778585db09866cbb37a7ab04eefc07b4df4>
- Log -----------------------------------------------------------------
commit ad9b9a4926e4b0d348c048937df69e382f7e6d27
Author: Tomasz Konojacki <m...@xenu.pl>
Date: Wed Nov 21 09:26:31 2018 +0100
optimize IV -> UV conversions
This commit replaces all instances of code that looks like this:
uv = (iv == IV_MIN) ? (UV)iv : (UV)(-iv)
with simpler and more optimal:
uv = -(UV)iv
While -iv indeed results in an undefined behaviour when iv == IV_MIN,
-(UV)iv is perfectly well defined and does the right thing.
C standard guarantees that the result of (UV)iv (for negative iv) is
equal to iv + UV_MAX + 1 (see 6.3.1.3, paragraph 2 in C11). It also
guarantees that the result of -uv is UV_MAX - uv + 1 (6.2.5,
paragraph 9).
That means that the result of -(UV)iv is UV_MAX - (iv + UV_MAX + 1) + 1
which is equal to -iv for *all* possible negative values of iv.
[perl #133677]
commit 9ba9a28aaea66bad2de041880a2c4210a911dda6
Author: David Mitchell <da...@iabyn.com>
Date: Wed Nov 21 12:09:45 2018 +0000
S_hv_delete_common(): avoid undefined behaviour
ASAN -fsanitize-undefined was tripping on the second of these two lines:
svp = AvARRAY(isa);
end = svp + AvFILLp(isa)+1;
In the case where svp is NULL and AvFILLp(isa) is -1, the first addition
is undefined behaviour. Add the 1 first, so that it becomes
svp + (-1+1), which is safe.
-----------------------------------------------------------------------
Summary of changes:
hv.c | 2 +-
pp.c | 18 +++++++++---------
pp_hot.c | 4 ++--
sv.c | 4 ++--
4 files changed, 14 insertions(+), 14 deletions(-)
diff --git a/hv.c b/hv.c
index d3d02d1046..fc90a5146b 100644
--- a/hv.c
+++ b/hv.c
@@ -1295,7 +1295,7 @@ S_hv_delete_common(pTHX_ HV *hv, SV *keysv, const char
*key, STRLEN klen,
SV **svp, **end;
strip_magic:
svp = AvARRAY(isa);
- end = svp + AvFILLp(isa)+1;
+ end = svp + (AvFILLp(isa)+1);
while (svp < end) {
if (*svp)
mg_free_type(*svp, PERL_MAGIC_isaelem);
diff --git a/pp.c b/pp.c
index 6d432acd31..880f266081 100644
--- a/pp.c
+++ b/pp.c
@@ -1319,7 +1319,7 @@ PP(pp_multiply)
auvok = TRUE; /* effectively it's a UV now */
} else {
/* abs, auvok == false records sign */
- alow = (aiv == IV_MIN) ? (UV)aiv : (UV)(-aiv);
+ alow = -(UV)aiv;
}
}
if (buvok) {
@@ -1331,7 +1331,7 @@ PP(pp_multiply)
buvok = TRUE; /* effectively it's a UV now */
} else {
/* abs, buvok == false records sign */
- blow = (biv == IV_MIN) ? (UV)biv : (UV)(-biv);
+ blow = -(UV)biv;
}
}
@@ -1462,7 +1462,7 @@ PP(pp_divide)
right_non_neg = TRUE; /* effectively it's a UV now */
}
else {
- right = (biv == IV_MIN) ? (UV)biv : (UV)(-biv);
+ right = -(UV)biv;
}
}
/* historically undef()/0 gives a "Use of uninitialized value"
@@ -1483,7 +1483,7 @@ PP(pp_divide)
left_non_neg = TRUE; /* effectively it's a UV now */
}
else {
- left = (aiv == IV_MIN) ? (UV)aiv : (UV)(-aiv);
+ left = -(UV)aiv;
}
}
@@ -1566,7 +1566,7 @@ PP(pp_modulo)
right = biv;
right_neg = FALSE; /* effectively it's a UV now */
} else {
- right = (biv == IV_MIN) ? (UV)biv : (UV)(-biv);
+ right = -(UV)biv;
}
}
}
@@ -1596,7 +1596,7 @@ PP(pp_modulo)
left = aiv;
left_neg = FALSE; /* effectively it's a UV now */
} else {
- left = (aiv == IV_MIN) ? (UV)aiv : (UV)(-aiv);
+ left = -(UV)aiv;
}
}
}
@@ -1893,8 +1893,8 @@ PP(pp_subtract)
if (aiv >= 0) {
auv = aiv;
auvok = 1; /* Now acting as a sign flag. */
- } else { /* 2s complement assumption for IV_MIN */
- auv = (aiv == IV_MIN) ? (UV)aiv : (UV)-aiv;
+ } else {
+ auv = -(UV)aiv;
}
}
a_valid = 1;
@@ -1914,7 +1914,7 @@ PP(pp_subtract)
buv = biv;
buvok = 1;
} else
- buv = (biv == IV_MIN) ? (UV)biv : (UV)-biv;
+ buv = -(UV)biv;
}
/* ?uvok if value is >= 0. basically, flagged as UV if it's +ve,
else "IV" now, independent of how it came in.
diff --git a/pp_hot.c b/pp_hot.c
index dc02612042..ace5f0208b 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -1521,7 +1521,7 @@ PP(pp_add)
auv = aiv;
auvok = 1; /* Now acting as a sign flag. */
} else {
- auv = (aiv == IV_MIN) ? (UV)aiv : (UV)(-aiv);
+ auv = -(UV)aiv;
}
}
a_valid = 1;
@@ -1541,7 +1541,7 @@ PP(pp_add)
buv = biv;
buvok = 1;
} else
- buv = (biv == IV_MIN) ? (UV)biv : (UV)(-biv);
+ buv = -(UV)biv;
}
/* ?uvok if value is >= 0. basically, flagged as UV if it's +ve,
else "IV" now, independent of how it came in.
diff --git a/sv.c b/sv.c
index 983646f335..b10f205033 100644
--- a/sv.c
+++ b/sv.c
@@ -2868,7 +2868,7 @@ S_uiv_2buf(char *const buf, const IV iv, UV uv, const int
is_uv, char **const pe
uv = iv;
sign = 0;
} else {
- uv = (iv == IV_MIN) ? (UV)iv : (UV)(-iv);
+ uv = -(UV)iv;
sign = 1;
}
do {
@@ -12596,7 +12596,7 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv, const char
*const pat, const STRLEN p
esignbuf[esignlen++] = plus;
}
else {
- uv = (iv == IV_MIN) ? (UV)iv : (UV)(-iv);
+ uv = -(UV)iv;
esignbuf[esignlen++] = '-';
}
}
--
Perl5 Master Repository
