math: Don't redirect inlined builtin math functions

When we want to inline builtin math functions, like truncf, for

  extern float truncf (float __x) __attribute__ ((__nothrow__ )) __attribute__ ((__const__));
  extern float __truncf (float __x) __attribute__ ((__nothrow__ )) __attribute__ ((__const__));

  float (truncf) (float) asm ("__truncf");

compiler may redirect truncf calls to __truncf, instead of inlining it
(for instance, clang).  The USE_TRUNCF_BUILTIN is 1 to indicate that
truncf should be inlined.  In this case, we don't want the truncf
redirection:

  1. For each math function which may be inlined, we define

  #if USE_TRUNCF_BUILTIN
   # define NO_truncf_BUILTIN inline_truncf
   #else
   # define NO_truncf_BUILTIN truncf
   #endif

in <math-use-builtins.h>.

  2. Include <math-use-builtins.h> in include/math.h.

  3. Change MATH_REDIRECT to

   #define MATH_REDIRECT(FUNC, PREFIX, ARGS)		\
    float (NO_ ## FUNC ## f ## _BUILTIN) (ARGS (float))	\
      asm (PREFIX #FUNC "f");

With this change If USE_TRUNCF_BUILTIN is 0, we get

  float (truncf) (float) asm ("__truncf");
  truncf will be redirected to __truncf.

And for USE_TRUNCF_BUILTIN 1, we get:

  float (inline_truncf) (float) asm ("__truncf");

In both cases either truncf will be inlined or the internal alias
(__truncf) will be called.

It is not required for all math-use-builtin symbol, only the one
defined in math.h.  It also allows to remove all the math-use-builtin
inclusion, since it is now implicitly included by math.h.

For MIPS, some math-use-builtin headers include sysdep.h and this
in turn includes a lot of extra headers that do not allow ldbl-128
code to override alias definition (math.h will include
some stdlib.h definition).  The math-use-builtin only requires
the __mips_isa_rev, so move the defintion to sgidefs.h.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Co-authored-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

1 files changed, 16 insertions, 6 deletions

diff --git a/include/math.h b/include/math.h
index 1236268804..84d44d44dc 100644
--- a/include/math.h
+++ b/include/math.h
@@ -139,25 +139,35 @@ fabsf128 (_Float128 x)
 /* NB: Internal tests don't have access to internal symbols.  */
 # if !IS_IN (testsuite_internal) \
      && !(defined __FINITE_MATH_ONLY__ && __FINITE_MATH_ONLY__ > 0)
+/* NO_MATH_REDIRECT must be defined in the source implementing function,
+   FUNC, if FUNC is implemented as an alias of __FUNC or vice versa to
+   avoid redirecting FUNC to __FUNC.  */
+# include <math-use-builtins.h>
+/* NB: Do not redirect math builtin functions when they are inlined.  */
 #  ifndef NO_MATH_REDIRECT
 /* Declare some functions for use within GLIBC.  Compilers typically
    inline those functions as a single instruction.  Use an asm to
    avoid use of PLTs if it doesn't.  */
 #   define MATH_REDIRECT(FUNC, PREFIX, ARGS)			\
-  float (FUNC ## f) (ARGS (float)) asm (PREFIX #FUNC "f");	\
-  double (FUNC) (ARGS (double)) asm (PREFIX #FUNC );		\
+  float (NO_ ## FUNC ## f ## _BUILTIN) (ARGS (float))		\
+    asm (PREFIX #FUNC "f");					\
+  double (NO_ ## FUNC ## _BUILTIN) (ARGS (double))		\
+    asm (PREFIX #FUNC );					\
   MATH_REDIRECT_LDBL (FUNC, PREFIX, ARGS)			\
   MATH_REDIRECT_F128 (FUNC, PREFIX, ARGS)
+
 #   if defined __NO_LONG_DOUBLE_MATH 				\
        || __LDOUBLE_REDIRECTS_TO_FLOAT128_ABI == 1
 #    define MATH_REDIRECT_LDBL(FUNC, PREFIX, ARGS)
 #   else
-#    define MATH_REDIRECT_LDBL(FUNC, PREFIX, ARGS)			\
-  long double (FUNC ## l) (ARGS (long double)) asm (PREFIX #FUNC "l");
+#    define MATH_REDIRECT_LDBL(FUNC, PREFIX, ARGS)		  \
+  long double (NO_ ## FUNC ## l ## _BUILTIN) (ARGS (long double)) \
+    asm (PREFIX #FUNC "l");
 #   endif
 #   if __HAVE_DISTINCT_FLOAT128
-#    define MATH_REDIRECT_F128(FUNC, PREFIX, ARGS)			\
-  _Float128 (FUNC ## f128) (ARGS (_Float128)) asm (PREFIX #FUNC "f128");
+#    define MATH_REDIRECT_F128(FUNC, PREFIX, ARGS)		 \
+  _Float128 (NO_ ## FUNC ## f128 ## _BUILTIN) (ARGS (_Float128)) \
+    asm (PREFIX #FUNC "f128");
 #   else
 #    define MATH_REDIRECT_F128(FUNC, PREFIX, ARGS)
 #   endif