165 lines
5.9 KiB
Diff
165 lines
5.9 KiB
Diff
From 548cc83c38a91852b1e44045ead3d20ccd5db4cf Mon Sep 17 00:00:00 2001
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From: Joseph Myers <joseph@codesourcery.com>
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Date: Thu, 28 Sep 2017 01:59:02 +0000
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Subject: [PATCH 42] Fix nearbyint arithmetic moved before feholdexcept (bug
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22225).
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In <https://sourceware.org/ml/libc-alpha/2013-05/msg00722.html> I
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remarked on the possibility of arithmetic in various nearbyint
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implementations being scheduled before feholdexcept calls, resulting
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in spurious "inexact" exceptions.
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I'm now actually observing this occurring in glibc built for ARM with
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GCC 7 (in fact, both copies of the same addition/subtraction sequence
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being combined and moved out before the conditionals and
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feholdexcept/fesetenv pairs), resulting in test failures.
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This patch makes the nearbyint implementations with this particular
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feholdexcept / arithmetic / fesetenv pattern consistently use
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math_opt_barrier on the function argument when first used in
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arithmetic, and also consistently use math_force_eval before fesetenv
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(the latter was generally already done, but the dbl-64/wordsize-64
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implementation used math_opt_barrier instead, and as
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math_opt_barrier's intended effect is through its output value being
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used, such a use that doesn't use the return value is suspect).
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Tested for x86_64 (--disable-multi-arch so more of these
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implementations get used), and for ARM in a configuration where I saw
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the problem scheduling.
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[BZ #22225]
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* sysdeps/ieee754/dbl-64/s_nearbyint.c (__nearbyint): Use
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math_opt_barrier on argument when doing arithmetic on it.
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* sysdeps/ieee754/dbl-64/wordsize-64/s_nearbyint.c (__nearbyint):
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Likewise. Use math_force_eval not math_opt_barrier after
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arithmetic.
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* sysdeps/ieee754/flt-32/s_nearbyintf.c (__nearbyintf): Use
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math_opt_barrier on argument when doing arithmetic on it.
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* sysdeps/ieee754/ldbl-128/s_nearbyintl.c (__nearbyintl):
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Likewise.
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(cherry picked from commit f124cb381116b5809de198327690ad0bd8d1478e)
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---
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ChangeLog | 13 +++++++++++++
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sysdeps/ieee754/dbl-64/s_nearbyint.c | 4 ++--
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sysdeps/ieee754/dbl-64/wordsize-64/s_nearbyint.c | 8 ++++----
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sysdeps/ieee754/flt-32/s_nearbyintf.c | 4 ++--
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sysdeps/ieee754/ldbl-128/s_nearbyintl.c | 4 ++--
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5 files changed, 23 insertions(+), 10 deletions(-)
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diff --git a/ChangeLog b/ChangeLog
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index 382674d5a3..992722acdb 100644
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--- a/ChangeLog
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+++ b/ChangeLog
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@@ -1,3 +1,16 @@
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+2017-09-28 Joseph Myers <joseph@codesourcery.com>
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+
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+ [BZ #22225]
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+ * sysdeps/ieee754/dbl-64/s_nearbyint.c (__nearbyint): Use
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+ math_opt_barrier on argument when doing arithmetic on it.
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+ * sysdeps/ieee754/dbl-64/wordsize-64/s_nearbyint.c (__nearbyint):
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+ Likewise. Use math_force_eval not math_opt_barrier after
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+ arithmetic.
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+ * sysdeps/ieee754/flt-32/s_nearbyintf.c (__nearbyintf): Use
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+ math_opt_barrier on argument when doing arithmetic on it.
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+ * sysdeps/ieee754/ldbl-128/s_nearbyintl.c (__nearbyintl):
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+ Likewise.
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+
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2017-09-22 Gabriel F. T. Gomes <gabriel@inconstante.eti.br>
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[BZ #22146]
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diff --git a/sysdeps/ieee754/dbl-64/s_nearbyint.c b/sysdeps/ieee754/dbl-64/s_nearbyint.c
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index dec0c5d6ee..6e3f8316b1 100644
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--- a/sysdeps/ieee754/dbl-64/s_nearbyint.c
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+++ b/sysdeps/ieee754/dbl-64/s_nearbyint.c
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@@ -48,7 +48,7 @@ __nearbyint (double x)
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if (j0 < 0)
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{
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libc_feholdexcept (&env);
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- w = TWO52[sx] + x;
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+ w = TWO52[sx] + math_opt_barrier (x);
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t = w - TWO52[sx];
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math_force_eval (t);
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libc_fesetenv (&env);
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@@ -65,7 +65,7 @@ __nearbyint (double x)
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return x; /* x is integral */
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}
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libc_feholdexcept (&env);
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- w = TWO52[sx] + x;
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+ w = TWO52[sx] + math_opt_barrier (x);
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t = w - TWO52[sx];
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math_force_eval (t);
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libc_fesetenv (&env);
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diff --git a/sysdeps/ieee754/dbl-64/wordsize-64/s_nearbyint.c b/sysdeps/ieee754/dbl-64/wordsize-64/s_nearbyint.c
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index 8293819981..7d135b54e4 100644
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--- a/sysdeps/ieee754/dbl-64/wordsize-64/s_nearbyint.c
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+++ b/sysdeps/ieee754/dbl-64/wordsize-64/s_nearbyint.c
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@@ -42,9 +42,9 @@ __nearbyint(double x)
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if(__builtin_expect(j0<52, 1)) {
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if(j0<0) {
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libc_feholdexcept (&env);
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- double w = TWO52[sx]+x;
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+ double w = TWO52[sx] + math_opt_barrier (x);
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double t = w-TWO52[sx];
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- math_opt_barrier(t);
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+ math_force_eval (t);
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libc_fesetenv (&env);
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return __copysign (t, x);
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}
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@@ -53,9 +53,9 @@ __nearbyint(double x)
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else return x; /* x is integral */
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}
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libc_feholdexcept (&env);
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- double w = TWO52[sx]+x;
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+ double w = TWO52[sx] + math_opt_barrier (x);
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double t = w-TWO52[sx];
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- math_opt_barrier (t);
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+ math_force_eval (t);
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libc_fesetenv (&env);
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return t;
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}
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diff --git a/sysdeps/ieee754/flt-32/s_nearbyintf.c b/sysdeps/ieee754/flt-32/s_nearbyintf.c
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index 5aebefafcf..b06df6b3c8 100644
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--- a/sysdeps/ieee754/flt-32/s_nearbyintf.c
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+++ b/sysdeps/ieee754/flt-32/s_nearbyintf.c
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@@ -37,7 +37,7 @@ __nearbyintf(float x)
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if(j0<23) {
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if(j0<0) {
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libc_feholdexceptf (&env);
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- w = TWO23[sx]+x;
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+ w = TWO23[sx] + math_opt_barrier (x);
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t = w-TWO23[sx];
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math_force_eval (t);
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libc_fesetenvf (&env);
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@@ -50,7 +50,7 @@ __nearbyintf(float x)
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else return x; /* x is integral */
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}
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libc_feholdexceptf (&env);
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- w = TWO23[sx]+x;
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+ w = TWO23[sx] + math_opt_barrier (x);
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t = w-TWO23[sx];
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math_force_eval (t);
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libc_fesetenvf (&env);
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diff --git a/sysdeps/ieee754/ldbl-128/s_nearbyintl.c b/sysdeps/ieee754/ldbl-128/s_nearbyintl.c
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index 1565a8183f..98a33d24a7 100644
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--- a/sysdeps/ieee754/ldbl-128/s_nearbyintl.c
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+++ b/sysdeps/ieee754/ldbl-128/s_nearbyintl.c
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@@ -45,7 +45,7 @@ _Float128 __nearbyintl(_Float128 x)
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if(j0<112) {
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if(j0<0) {
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feholdexcept (&env);
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- w = TWO112[sx]+x;
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+ w = TWO112[sx] + math_opt_barrier (x);
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t = w-TWO112[sx];
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math_force_eval (t);
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fesetenv (&env);
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@@ -58,7 +58,7 @@ _Float128 __nearbyintl(_Float128 x)
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else return x; /* x is integral */
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}
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feholdexcept (&env);
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- w = TWO112[sx]+x;
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+ w = TWO112[sx] + math_opt_barrier (x);
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t = w-TWO112[sx];
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math_force_eval (t);
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fesetenv (&env);
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