From 0fe0f1f86f82f9e08ca4d4b85111de03f4c2f876 Mon Sep 17 00:00:00 2001
From: Richard Henderson <rth@twiddle.net>
Date: Sat, 10 Mar 2012 08:53:05 -0800
Subject: Create and use libc_feupdateenv_test.

We can reduce the number of STMXCSR, and often we can avoid the
call to __feraiseexcept.
---
 sysdeps/x86_64/fpu/math_private.h | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

(limited to 'sysdeps/x86_64')

diff --git a/sysdeps/x86_64/fpu/math_private.h b/sysdeps/x86_64/fpu/math_private.h
index 3289afc58b..aa208b2e18 100644
--- a/sysdeps/x86_64/fpu/math_private.h
+++ b/sysdeps/x86_64/fpu/math_private.h
@@ -108,13 +108,33 @@ libc_fesetenv (fenv_t *e)
 #define libc_fesetenv  libc_fesetenv
 #define libc_fesetenvf libc_fesetenv
 
+static __always_inline int
+libc_feupdateenv_test (fenv_t *e, int ex)
+{
+  unsigned int mxcsr, old_mxcsr, cur_ex;
+  asm volatile (STMXCSR " %0" : "=m" (*&mxcsr));
+  cur_ex = mxcsr & FE_ALL_EXCEPT;
+
+  /* Merge current exceptions with the old environment.  */
+  old_mxcsr = e->__mxcsr;
+  mxcsr = old_mxcsr | cur_ex;
+  asm volatile (LDMXCSR " %0" : : "m" (*&mxcsr));
+
+  /* Raise SIGFPE for any new exceptions since the hold.  Expect that
+     the normal environment has all exceptions masked.  */
+  if (__builtin_expect ((old_mxcsr >> 7) & cur_ex, 0))
+    __feraiseexcept (cur_ex);
+
+  /* Test for exceptions raised since the hold.  */
+  return cur_ex & ex;
+}
+#define libc_feupdateenv_test  libc_feupdateenv_test
+#define libc_feupdateenv_testf libc_feupdateenv_test
+
 static __always_inline void
 libc_feupdateenv (fenv_t *e)
 {
-  unsigned int mxcsr;
-  asm volatile (STMXCSR " %0" : "=m" (*&mxcsr));
-  asm volatile (LDMXCSR " %0" : : "m" ((e)->__mxcsr));
-  __feraiseexcept (mxcsr & FE_ALL_EXCEPT);
+  libc_feupdateenv_test (e, 0);
 }
 #define libc_feupdateenv  libc_feupdateenv
 #define libc_feupdateenvf libc_feupdateenv
-- 
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