[RFC] Enable math functions linking with static library for LTO

[Xiong Hu Luo]

In LTO mode, if static library and dynamic library contains same
function and both libraries are passed as arguments, linker will link
the function in dynamic library no matter the sequence.  This patch
will output LTO symbol node as UNDEF if BUILT_IN_NORMAL function FNDECL
is a math function, then the function in static library will be linked
first if its sequence is ahead of the dynamic library.

gcc/ChangeLog

	2019-08-09  Xiong Hu Luo  <luoxhu@linux.ibm.com>

	PR lto/91287
	* symtab.c (write_symbol): Check built_in function type.
	* lto-streamer-out.c (symtab_node::output_to_lto_symbol_table_p):
	Return true if built_in function is a math BUILT_IN_NORMAL function.
---
 gcc/lto-streamer-out.c |  5 ++-
 gcc/symtab.c           | 84 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 86 insertions(+), 3 deletions(-)

diff --git a/gcc/lto-streamer-out.c b/gcc/lto-streamer-out.c
index 47a9143ae26..9d42a57b4b6 100644
--- a/gcc/lto-streamer-out.c
+++ b/gcc/lto-streamer-out.c
@@ -2644,7 +2644,10 @@ write_symbol (struct streamer_tree_cache_d *cache,
 
   gcc_checking_assert (TREE_PUBLIC (t)
 		       && (TREE_CODE (t) != FUNCTION_DECL
-			   || !fndecl_built_in_p (t))
+			   || !fndecl_built_in_p (t, BUILT_IN_MD))
+		       && (TREE_CODE (t) != FUNCTION_DECL
+			   || !fndecl_built_in_p (t, BUILT_IN_NORMAL)
+			   || associated_internal_fn (t) != IFN_LAST)
 		       && !DECL_ABSTRACT_P (t)
 		       && (!VAR_P (t) || !DECL_HARD_REGISTER (t)));
 
diff --git a/gcc/symtab.c b/gcc/symtab.c
index 63e2820eb93..34bdccd7f6e 100644
--- a/gcc/symtab.c
+++ b/gcc/symtab.c
@@ -2377,8 +2377,88 @@ symtab_node::output_to_lto_symbol_table_p (void)
     return false;
   /* FIXME: Builtins corresponding to real functions probably should have
      symbol table entries.  */
-  if (TREE_CODE (decl) == FUNCTION_DECL && fndecl_built_in_p (decl))
-    return false;
+  if (TREE_CODE (decl) == FUNCTION_DECL && !definition
+      && fndecl_built_in_p (decl))
+    {
+      if (DECL_BUILT_IN_CLASS (decl) == BUILT_IN_NORMAL)
+	switch (DECL_FUNCTION_CODE (decl))
+	  {
+	    CASE_FLT_FN (BUILT_IN_ACOS):
+	    CASE_FLT_FN (BUILT_IN_ACOSH):
+	    CASE_FLT_FN (BUILT_IN_ASIN):
+	    CASE_FLT_FN (BUILT_IN_ASINH):
+	    CASE_FLT_FN (BUILT_IN_ATAN):
+	    CASE_FLT_FN (BUILT_IN_ATANH):
+	    CASE_FLT_FN (BUILT_IN_ATAN2):
+	    CASE_FLT_FN (BUILT_IN_CBRT):
+	    CASE_FLT_FN (BUILT_IN_CEIL):
+	    CASE_FLT_FN_FLOATN_NX (BUILT_IN_CEIL):
+	    CASE_FLT_FN (BUILT_IN_COPYSIGN):
+	    CASE_FLT_FN_FLOATN_NX (BUILT_IN_COPYSIGN):
+	    CASE_FLT_FN (BUILT_IN_COS):
+	    CASE_FLT_FN (BUILT_IN_COSH):
+	    CASE_FLT_FN (BUILT_IN_ERF):
+	    CASE_FLT_FN (BUILT_IN_ERFC):
+	    CASE_FLT_FN (BUILT_IN_EXP):
+	    CASE_FLT_FN (BUILT_IN_EXP2):
+	    CASE_FLT_FN (BUILT_IN_EXPM1):
+	    CASE_FLT_FN (BUILT_IN_FABS):
+	    CASE_FLT_FN_FLOATN_NX (BUILT_IN_FABS):
+	    CASE_FLT_FN (BUILT_IN_FDIM):
+	    CASE_FLT_FN (BUILT_IN_FLOOR):
+	    CASE_FLT_FN_FLOATN_NX (BUILT_IN_FLOOR):
+	    CASE_FLT_FN (BUILT_IN_FMA):
+	    CASE_FLT_FN_FLOATN_NX (BUILT_IN_FMA):
+	    CASE_FLT_FN (BUILT_IN_FMAX):
+	    CASE_FLT_FN_FLOATN_NX (BUILT_IN_FMAX):
+	    CASE_FLT_FN (BUILT_IN_FMIN):
+	    CASE_FLT_FN_FLOATN_NX (BUILT_IN_FMIN):
+	    CASE_FLT_FN (BUILT_IN_FMOD):
+	    CASE_FLT_FN (BUILT_IN_FREXP):
+	    CASE_FLT_FN (BUILT_IN_HYPOT):
+	    CASE_FLT_FN (BUILT_IN_ILOGB):
+	    CASE_FLT_FN (BUILT_IN_LDEXP):
+	    CASE_FLT_FN (BUILT_IN_LGAMMA):
+	    CASE_FLT_FN (BUILT_IN_LLRINT):
+	    CASE_FLT_FN (BUILT_IN_LLROUND):
+	    CASE_FLT_FN (BUILT_IN_LOG):
+	    CASE_FLT_FN (BUILT_IN_LOG10):
+	    CASE_FLT_FN (BUILT_IN_LOG1P):
+	    CASE_FLT_FN (BUILT_IN_LOG2):
+	    CASE_FLT_FN (BUILT_IN_LOGB):
+	    CASE_FLT_FN (BUILT_IN_LRINT):
+	    CASE_FLT_FN (BUILT_IN_LROUND):
+	    CASE_FLT_FN (BUILT_IN_MODF):
+	    CASE_FLT_FN (BUILT_IN_NAN):
+	    CASE_FLT_FN (BUILT_IN_NEARBYINT):
+	    CASE_FLT_FN_FLOATN_NX (BUILT_IN_NEARBYINT):
+	    CASE_FLT_FN (BUILT_IN_NEXTAFTER):
+	    CASE_FLT_FN (BUILT_IN_NEXTTOWARD):
+	    CASE_FLT_FN (BUILT_IN_POW):
+	    CASE_FLT_FN (BUILT_IN_REMAINDER):
+	    CASE_FLT_FN (BUILT_IN_REMQUO):
+	    CASE_FLT_FN (BUILT_IN_RINT):
+	    CASE_FLT_FN_FLOATN_NX (BUILT_IN_RINT):
+	    CASE_FLT_FN (BUILT_IN_ROUND):
+	    CASE_FLT_FN_FLOATN_NX (BUILT_IN_ROUND):
+	    CASE_FLT_FN (BUILT_IN_SCALBLN):
+	    CASE_FLT_FN (BUILT_IN_SCALBN):
+	    CASE_FLT_FN (BUILT_IN_SIN):
+	    CASE_FLT_FN (BUILT_IN_SINH):
+	    CASE_FLT_FN (BUILT_IN_SINCOS):
+	    CASE_FLT_FN (BUILT_IN_SQRT):
+	    CASE_FLT_FN_FLOATN_NX (BUILT_IN_SQRT):
+	    CASE_FLT_FN (BUILT_IN_TAN):
+	    CASE_FLT_FN (BUILT_IN_TANH):
+	    CASE_FLT_FN (BUILT_IN_TGAMMA):
+	    CASE_FLT_FN (BUILT_IN_TRUNC):
+	    CASE_FLT_FN_FLOATN_NX (BUILT_IN_TRUNC):
+	      return true;
+	  default:
+	    break;
+	  }
+      return false;
+    }
 
   /* We have real symbol that should be in symbol table.  However try to trim
      down the refernces to libraries bit more because linker will otherwise
-- 
2.21.0.777.g83232e3864