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Avoid "inexact" exceptions in i386/x86_64 trunc functions (bug 15479)

From: Joseph Myers <joseph at codesourcery dot com>
To: <libc-alpha at sourceware dot org>
Date: Wed, 22 Jun 2016 17:22:52 +0000
Subject: Avoid "inexact" exceptions in i386/x86_64 trunc functions (bug 15479)
Authentication-results: sourceware.org; auth=none
As discussed in
<https://sourceware.org/ml/libc-alpha/2016-05/msg00577.html>, TS
18661-1 disallows ceil, floor, round and trunc functions from raising
the "inexact" exception, in accordance with general IEEE 754 semantics
for when that exception is raised.  Fixing this for x87 floating point
is more complicated than for the other versions of these functions,
because they use the frndint instruction that raises "inexact" and
this can only be avoided by saving and restoring the whole
floating-point environment.

As I noted in
<https://sourceware.org/ml/libc-alpha/2016-06/msg00128.html>, I have
now implemented a GCC option -fno-fp-int-builtin-inexact for GCC 7,
such that GCC will inline these functions on x86, without caring about
"inexact", when the default -ffp-int-builtin-inexact is in effect.
This allows users to get optimized code depending on the options they
pass to the compiler, while making the out-of-line functions follow TS
18661-1 semantics and avoid "inexact".

This patch duly fixes the out-of-line trunc function implementations
to avoid "inexact", in the same way as the nearbyint implementations.

I do not know how the performance of implementations such as these
based on saving the environment and changing the rounding mode
temporarily compares to that of the C versions or SSE 4.1 versions (of
course, for 32-bit x86 SSE implementations still need to get the
return value in an x87 register); it's entirely possible other
implementations could be faster in some cases.

Tested for x86_64 and x86.  I intend to commit this, and corresponding 
ceil and floor fixes, in the absence of further comments.

2016-06-22  Joseph Myers  <joseph@codesourcery.com>

	[BZ #15479]
	* sysdeps/i386/fpu/s_trunc.S (__trunc): Save and restore
	floating-point environment rather than just control word.
	* sysdeps/i386/fpu/s_truncf.S (__truncf): Likewise.
	* sysdeps/i386/fpu/s_truncl.S (__truncl): Save and restore
	floating-point environment, with "invalid" exceptions merged in,
	rather than just control word.
	* sysdeps/x86_64/fpu/s_truncl.S (__truncl): Likewise.
	* math/libm-test.inc (trunc_test_data): Do not allow spurious
	"inexact" exceptions.

diff --git a/math/libm-test.inc b/math/libm-test.inc
index 17d65b4..a4983b6 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -11827,9 +11827,8 @@ static const struct test_f_f_data trunc_test_data[] =
 
     TEST_f_f (trunc, 0, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_f (trunc, minus_zero, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
-    /* Bug 15479: spurious "inexact" exception may occur.  */
-    TEST_f_f (trunc, min_subnorm_value, 0.0, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, min_value, 0.0, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, min_subnorm_value, 0.0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, min_value, 0.0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_f (trunc, 1, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_f (trunc, 2, 2, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_f (trunc, 0x1p23, 0x1p23, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
@@ -11848,8 +11847,8 @@ static const struct test_f_f_data trunc_test_data[] =
     TEST_f_f (trunc, 0x1p113, 0x1p113, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_f (trunc, 0x1p114, 0x1p114, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_f (trunc, max_value, max_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -min_subnorm_value, minus_zero, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -min_value, minus_zero, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -min_subnorm_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -min_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_f (trunc, -1, -1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_f (trunc, -2, -2, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_f (trunc, -0x1p23, -0x1p23, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
@@ -11869,108 +11868,108 @@ static const struct test_f_f_data trunc_test_data[] =
     TEST_f_f (trunc, -0x1p114, -0x1p114, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_f (trunc, -max_value, -max_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 
-    TEST_f_f (trunc, 0.1, 0, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 0.25, 0, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 0.625, 0, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -0.1, minus_zero, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -0.25, minus_zero, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -0.625, minus_zero, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 0.1, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 0.25, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 0.625, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -0.1, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -0.25, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -0.625, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_f (trunc, 1, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_f (trunc, -1, -1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 1.625, 1, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -1.625, -1, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 1.625, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -1.625, -1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 
-    TEST_f_f (trunc, 1048580.625L, 1048580L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -1048580.625L, -1048580L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 1048580.625L, 1048580L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -1048580.625L, -1048580L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 
-    TEST_f_f (trunc, 8388610.125L, 8388610.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -8388610.125L, -8388610.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 8388610.125L, 8388610.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -8388610.125L, -8388610.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 
-    TEST_f_f (trunc, 4294967296.625L, 4294967296.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -4294967296.625L, -4294967296.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 4294967296.625L, 4294967296.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -4294967296.625L, -4294967296.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 
 #if MANT_DIG >= 64
     /* The result can only be represented in long double.  */
-    TEST_f_f (trunc, 4503599627370495.5L, 4503599627370495.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 4503599627370496.25L, 4503599627370496.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 4503599627370496.5L, 4503599627370496.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 4503599627370496.75L, 4503599627370496.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 4503599627370497.5L, 4503599627370497.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 4503599627370495.5L, 4503599627370495.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 4503599627370496.25L, 4503599627370496.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 4503599627370496.5L, 4503599627370496.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 4503599627370496.75L, 4503599627370496.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 4503599627370497.5L, 4503599627370497.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 
 # if MANT_DIG > 100
-    TEST_f_f (trunc, 4503599627370494.5000000000001L, 4503599627370494.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 4503599627370495.5000000000001L, 4503599627370495.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 4503599627370496.5000000000001L, 4503599627370496.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 4503599627370494.5000000000001L, 4503599627370494.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 4503599627370495.5000000000001L, 4503599627370495.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 4503599627370496.5000000000001L, 4503599627370496.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 # endif
 
-    TEST_f_f (trunc, -4503599627370495.5L, -4503599627370495.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -4503599627370496.25L, -4503599627370496.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -4503599627370496.5L, -4503599627370496.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -4503599627370496.75L, -4503599627370496.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -4503599627370497.5L, -4503599627370497.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -4503599627370495.5L, -4503599627370495.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -4503599627370496.25L, -4503599627370496.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -4503599627370496.5L, -4503599627370496.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -4503599627370496.75L, -4503599627370496.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -4503599627370497.5L, -4503599627370497.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 
 # if MANT_DIG > 100
-    TEST_f_f (trunc, -4503599627370494.5000000000001L, -4503599627370494.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -4503599627370495.5000000000001L, -4503599627370495.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -4503599627370496.5000000000001L, -4503599627370496.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -4503599627370494.5000000000001L, -4503599627370494.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -4503599627370495.5000000000001L, -4503599627370495.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -4503599627370496.5000000000001L, -4503599627370496.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 # endif
 
-    TEST_f_f (trunc, 9007199254740991.5L, 9007199254740991.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 9007199254740992.25L, 9007199254740992.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 9007199254740992.5L, 9007199254740992.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 9007199254740992.75L, 9007199254740992.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 9007199254740993.5L, 9007199254740993.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 9007199254740991.5L, 9007199254740991.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 9007199254740992.25L, 9007199254740992.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 9007199254740992.5L, 9007199254740992.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 9007199254740992.75L, 9007199254740992.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 9007199254740993.5L, 9007199254740993.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 
 # if MANT_DIG > 100
-    TEST_f_f (trunc, 9007199254740991.0000000000001L, 9007199254740991.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 9007199254740992.0000000000001L, 9007199254740992.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 9007199254740993.0000000000001L, 9007199254740993.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 9007199254740991.5000000000001L, 9007199254740991.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 9007199254740992.5000000000001L, 9007199254740992.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 9007199254740993.5000000000001L, 9007199254740993.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 9007199254740991.0000000000001L, 9007199254740991.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 9007199254740992.0000000000001L, 9007199254740992.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 9007199254740993.0000000000001L, 9007199254740993.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 9007199254740991.5000000000001L, 9007199254740991.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 9007199254740992.5000000000001L, 9007199254740992.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 9007199254740993.5000000000001L, 9007199254740993.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 # endif
 
-    TEST_f_f (trunc, -9007199254740991.5L, -9007199254740991.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -9007199254740992.25L, -9007199254740992.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -9007199254740992.5L, -9007199254740992.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -9007199254740992.75L, -9007199254740992.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -9007199254740993.5L, -9007199254740993.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -9007199254740991.5L, -9007199254740991.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -9007199254740992.25L, -9007199254740992.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -9007199254740992.5L, -9007199254740992.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -9007199254740992.75L, -9007199254740992.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -9007199254740993.5L, -9007199254740993.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 
 # if MANT_DIG > 100
-    TEST_f_f (trunc, -9007199254740991.0000000000001L, -9007199254740991.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -9007199254740992.0000000000001L, -9007199254740992.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -9007199254740993.0000000000001L, -9007199254740993.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -9007199254740991.5000000000001L, -9007199254740991.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -9007199254740992.5000000000001L, -9007199254740992.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -9007199254740993.5000000000001L, -9007199254740993.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -9007199254740991.0000000000001L, -9007199254740991.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -9007199254740992.0000000000001L, -9007199254740992.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -9007199254740993.0000000000001L, -9007199254740993.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -9007199254740991.5000000000001L, -9007199254740991.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -9007199254740992.5000000000001L, -9007199254740992.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -9007199254740993.5000000000001L, -9007199254740993.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 # endif
 
-    TEST_f_f (trunc, 72057594037927935.5L, 72057594037927935.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 72057594037927936.25L, 72057594037927936.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 72057594037927936.5L, 72057594037927936.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 72057594037927936.75L, 72057594037927936.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 72057594037927937.5L, 72057594037927937.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 72057594037927935.5L, 72057594037927935.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 72057594037927936.25L, 72057594037927936.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 72057594037927936.5L, 72057594037927936.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 72057594037927936.75L, 72057594037927936.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 72057594037927937.5L, 72057594037927937.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 
-    TEST_f_f (trunc, -72057594037927935.5L, -72057594037927935.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -72057594037927936.25L, -72057594037927936.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -72057594037927936.5L, -72057594037927936.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -72057594037927936.75L, -72057594037927936.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -72057594037927937.5L, -72057594037927937.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -72057594037927935.5L, -72057594037927935.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -72057594037927936.25L, -72057594037927936.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -72057594037927936.5L, -72057594037927936.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -72057594037927936.75L, -72057594037927936.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -72057594037927937.5L, -72057594037927937.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 
     /* Check cases where first double is a exact integer higher than 2^52 and
        the precision is determined by second long double for IBM long double.  */
-    TEST_f_f (trunc,  34503599627370498.515625L, 34503599627370498.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -34503599627370498.515625L, -34503599627370498.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc,  34503599627370498.515625L, 34503599627370498.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -34503599627370498.515625L, -34503599627370498.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 # if MANT_DIG >= 106
-    TEST_f_f (trunc,  1192568192774434123539907640624.484375L, 1192568192774434123539907640624.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, -1192568192774434123539907640624.484375L, -1192568192774434123539907640624.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc,  1192568192774434123539907640624.484375L, 1192568192774434123539907640624.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, -1192568192774434123539907640624.484375L, -1192568192774434123539907640624.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 # endif
 
-    TEST_f_f (trunc, 10141204801825835211973625643007.5L, 10141204801825835211973625643007.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 10141204801825835211973625643008.25L, 10141204801825835211973625643008.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 10141204801825835211973625643008.5L, 10141204801825835211973625643008.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 10141204801825835211973625643008.75L, 10141204801825835211973625643008.0L, ERRNO_UNCHANGED),
-    TEST_f_f (trunc, 10141204801825835211973625643009.5L, 10141204801825835211973625643009.0L, ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 10141204801825835211973625643007.5L, 10141204801825835211973625643007.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 10141204801825835211973625643008.25L, 10141204801825835211973625643008.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 10141204801825835211973625643008.5L, 10141204801825835211973625643008.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 10141204801825835211973625643008.75L, 10141204801825835211973625643008.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (trunc, 10141204801825835211973625643009.5L, 10141204801825835211973625643009.0L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 #endif
   };
 
diff --git a/sysdeps/i386/fpu/s_trunc.S b/sysdeps/i386/fpu/s_trunc.S
index a15e5e5..8d9a6df 100644
--- a/sysdeps/i386/fpu/s_trunc.S
+++ b/sysdeps/i386/fpu/s_trunc.S
@@ -21,17 +21,17 @@
 
 ENTRY(__trunc)
 	fldl	4(%esp)
-	subl	$8, %esp
-	cfi_adjust_cfa_offset (8)
-	fstcw	4(%esp)
+	subl	$32, %esp
+	cfi_adjust_cfa_offset (32)
+	fnstenv	4(%esp)
 	movl	$0xc00, %edx
 	orl	4(%esp), %edx
 	movl	%edx, (%esp)
 	fldcw	(%esp)
 	frndint
-	fldcw	4(%esp)
-	addl	$8, %esp
-	cfi_adjust_cfa_offset (-8)
+	fldenv	4(%esp)
+	addl	$32, %esp
+	cfi_adjust_cfa_offset (-32)
 	ret
 END(__trunc)
 weak_alias (__trunc, trunc)
diff --git a/sysdeps/i386/fpu/s_truncf.S b/sysdeps/i386/fpu/s_truncf.S
index cbf257a..d55a11d 100644
--- a/sysdeps/i386/fpu/s_truncf.S
+++ b/sysdeps/i386/fpu/s_truncf.S
@@ -21,17 +21,17 @@
 
 ENTRY(__truncf)
 	flds	4(%esp)
-	subl	$8, %esp
-	cfi_adjust_cfa_offset (8)
-	fstcw	4(%esp)
+	subl	$32, %esp
+	cfi_adjust_cfa_offset (32)
+	fnstenv	4(%esp)
 	movl	$0xc00, %edx
 	orl	4(%esp), %edx
 	movl	%edx, (%esp)
 	fldcw	(%esp)
 	frndint
-	fldcw	4(%esp)
-	addl	$8, %esp
-	cfi_adjust_cfa_offset (-8)
+	fldenv	4(%esp)
+	addl	$32, %esp
+	cfi_adjust_cfa_offset (-32)
 	ret
 END(__truncf)
 weak_alias (__truncf, truncf)
diff --git a/sysdeps/i386/fpu/s_truncl.S b/sysdeps/i386/fpu/s_truncl.S
index f92b474..f5ba372 100644
--- a/sysdeps/i386/fpu/s_truncl.S
+++ b/sysdeps/i386/fpu/s_truncl.S
@@ -21,17 +21,20 @@
 
 ENTRY(__truncl)
 	fldt	4(%esp)
-	subl	$8, %esp
-	cfi_adjust_cfa_offset (8)
-	fstcw	4(%esp)
+	subl	$32, %esp
+	cfi_adjust_cfa_offset (32)
+	fnstenv	4(%esp)
 	movl	$0xc00, %edx
 	orl	4(%esp), %edx
 	movl	%edx, (%esp)
 	fldcw	(%esp)
 	frndint
-	fldcw	4(%esp)
-	addl	$8, %esp
-	cfi_adjust_cfa_offset (-8)
+	fnstsw
+	andl	$0x1, %eax
+	orl	%eax, 8(%esp)
+	fldenv	4(%esp)
+	addl	$32, %esp
+	cfi_adjust_cfa_offset (-32)
 	ret
 END(__truncl)
 weak_alias (__truncl, truncl)
diff --git a/sysdeps/x86_64/fpu/s_truncl.S b/sysdeps/x86_64/fpu/s_truncl.S
index c37cf00..0b46efe 100644
--- a/sysdeps/x86_64/fpu/s_truncl.S
+++ b/sysdeps/x86_64/fpu/s_truncl.S
@@ -21,13 +21,16 @@
 
 ENTRY(__truncl)
 	fldt	8(%rsp)
-	fstcw	-4(%rsp)
+	fnstenv	-28(%rsp)
 	movl	$0xc00, %edx
-	orl	-4(%rsp), %edx
-	movl	%edx, -8(%rsp)
-	fldcw	-8(%rsp)
+	orl	-28(%rsp), %edx
+	movl	%edx, -32(%rsp)
+	fldcw	-32(%rsp)
 	frndint
-	fldcw	-4(%rsp)
+	fnstsw
+	andl	$0x1, %eax
+	orl	%eax, -24(%rsp)
+	fldenv	-28(%rsp)
 	ret
 END(__truncl)
 weak_alias (__truncl, truncl)

-- 
Joseph S. Myers
joseph@codesourcery.com
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