[Patch v2] Enable math functions linking with static library for LTO

[luoxhu <luoxhu at linux dot ibm dot com>]

Hi Richard,
Thanks for your comments, updated the v2 patch as below:
1. Define and use builtin_with_linkage_p.
2. Add comments.
3. Add a testcase.

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

	2019-08-12  Xiong Hu Luo  <luoxhu@linux.ibm.com>

	PR lto/91287
	* builtins.c (builtin_with_linkage_p): New function.
	* builtins.h (builtin_with_linkage_p): New function.
	* symtab.c (write_symbol): Use builtin_with_linkage_p.
	* lto-streamer-out.c (symtab_node::output_to_lto_symbol_table_p):
	Likewise.

gcc/testsuite/ChangeLog

	2019-08-12  Xiong Hu Luo  <luoxhu@linux.ibm.com>

	PR lto/91287
	* gcc.dg/pr91287.c: New testcase.
---
 gcc/builtins.c                 | 89 ++++++++++++++++++++++++++++++++++
 gcc/builtins.h                 |  2 +
 gcc/lto-streamer-out.c         |  4 +-
 gcc/symtab.c                   | 13 ++++-
 gcc/testsuite/gcc.dg/pr91287.c | 40 +++++++++++++++
 5 files changed, 145 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/pr91287.c

diff --git a/gcc/builtins.c b/gcc/builtins.c
index 695a9d191af..f4dea941a27 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -11244,3 +11244,92 @@ target_char_cst_p (tree t, char *p)
   *p = (char)tree_to_uhwi (t);
   return true;
 }
+
+/* Return true if DECL is a specified builtin math function.  These functions
+   should have symbol in symbol table to provide linkage with faster version of
+   libraries.  */
+
+bool
+builtin_with_linkage_p (tree decl)
+{
+  if (!decl)
+    return false;
+  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;
+}
diff --git a/gcc/builtins.h b/gcc/builtins.h
index 1ffb491d785..91cbd81be48 100644
--- a/gcc/builtins.h
+++ b/gcc/builtins.h
@@ -151,4 +151,6 @@ extern internal_fn replacement_internal_fn (gcall *);
 extern void warn_string_no_nul (location_t, const char *, tree, tree);
 extern tree unterminated_array (tree, tree * = NULL, bool * = NULL);
 
+extern bool builtin_with_linkage_p (tree);
+
 #endif /* GCC_BUILTINS_H */
diff --git a/gcc/lto-streamer-out.c b/gcc/lto-streamer-out.c
index 47a9143ae26..73bf45810f0 100644
--- a/gcc/lto-streamer-out.c
+++ b/gcc/lto-streamer-out.c
@@ -2644,7 +2644,9 @@ write_symbol (struct streamer_tree_cache_d *cache,
 
   gcc_checking_assert (TREE_PUBLIC (t)
 		       && (TREE_CODE (t) != FUNCTION_DECL
-			   || !fndecl_built_in_p (t))
+			   || cgraph_node::get (t)->definition
+			   || !fndecl_built_in_p (t, BUILT_IN_NORMAL)
+			   || builtin_with_linkage_p (t))
 		       && !DECL_ABSTRACT_P (t)
 		       && (!VAR_P (t) || !DECL_HARD_REGISTER (t)));
 
diff --git a/gcc/symtab.c b/gcc/symtab.c
index 63e2820eb93..e806afdede4 100644
--- a/gcc/symtab.c
+++ b/gcc/symtab.c
@@ -2377,8 +2377,17 @@ 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))
+    {
+      /* Math functions may have faster version in static library, output the
+	 symbol for linkage.  Functions have implementation in libgcc will be
+	 excluded as the symbol name may mismatch.  */
+      if (builtin_with_linkage_p (decl))
+	return true;
+      else
+	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
diff --git a/gcc/testsuite/gcc.dg/pr91287.c b/gcc/testsuite/gcc.dg/pr91287.c
new file mode 100644
index 00000000000..c816e0537aa
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr91287.c
@@ -0,0 +1,40 @@
+/* { dg-do assemble } */
+/* { dg-options "-O2" } */
+
+#include <stdio.h>
+#include <string.h>
+#include <math.h>
+#include <stdlib.h>
+
+double __attribute__((noinline)) zowie (double x, double y, double z)
+{
+  x = __builtin_clz(x);
+  return atan2 (x * y, z);
+}
+
+double __attribute__((noinline)) rand_finite_double (void)
+{
+  union {
+    double d;
+    unsigned char uc[sizeof(double)];
+  } u;
+  do {
+    for (unsigned i = 0; i < sizeof u.uc; i++) {
+      u.uc[i] = (unsigned char) rand();
+    }
+  } while (!isfinite(u.d));
+  return u.d;
+}
+
+
+int main ()
+{
+  char str[100];
+  strcpy(str, "test\n");
+  double a = rand_finite_double ();
+  printf ("%lf, %s\n", zowie (a, 4.5, 2.2), str);
+  return 0;
+}
+
+/* { dg-final { scan-symbol "atan2" } } */
+/* { dg-final { scan-symbol-not "__builtin_clz" } } */
-- 
2.21.0.777.g83232e3864