Extend tree-call-cdce to calls whose result is used

For -fmath-errno, builtins.c currently expands calls to sqrt to:

        y = sqrt_optab (x);
        if (y != y)
          [ sqrt (x); or errno = EDOM; ]

The drawbacks of this are:

- the call to sqrt is protected by the result of the optab rather
      than the input.  It would be better to check __builtin_isless (x, 0),
      like tree-call-cdce.c does.

- the branch isn't exposed at the gimple level and so gets little
      high-level optimisation.

- we do this for log too, but for log a zero input produces
      -inf rather than a NaN, and sets errno to ERANGE rather than EDOM.

This patch moves the code to tree-call-cdce.c instead, with the optab
operation being represented as an internal function.  This means that
we can use the existing argument-based range checks rather than the
result-based checks and that we get more gimple optimisation of
the branch.

Previously the pass was only enabled by default at -O2 or above,
but the old builtins.c code was enabled at -O.  The patch therefore
enables the pass at -O as well.

The previous patch to cfgexpand.c handled cases where functions
don't (or are assumed not to) set errno, so this patch makes
the builtins.c code dead.

Tested on x86_64-linux-gnu, aarch64-linux-gnu, arm-linux-gnueabi
and visium-elf (for the EDOM stuff).

gcc/
	* builtins.c (expand_errno_check, expand_builtin_mathfn)
	(expand_builtin_mathfn_2): Delete.
	(expand_builtin): Remove handling of functions with
	internal function equivalents.
	* internal-fn.def (SET_EDOM): New internal function.
	* internal-fn.h (set_edom_supported_p): Declare.
	* internal-fn.c (expand_SET_EDOM): New function.
	(set_edom_supported_p): Likewise.
	* tree-call-cdce.c: Include builtins.h and internal-fn.h.
	Rewrite comment at head of file.
	(is_call_dce_candidate): Rename to...
	(can_test_argument_range): ...this.  Don't check gimple_call_lhs
	or gimple_call_builtin_p here.
	(edom_only_function): New function.
	(shrink_wrap_one_built_in_call_with_conds): New function, split out
	from...
	(shrink_wrap_one_built_in_call): ...here.
	(can_use_internal_fn, use_internal_fn): New functions.
	(shrink_wrap_conditional_dead_built_in_calls): Call use_internal_fn
	for calls that have an lhs.
	(pass_call_cdce::gate): Remove optimize_function_for_speed_p check.
	(pass_call_cdce::execute): Skip blocks that are optimized for size.
	Check gimple_call_builtin_p here.  Use can_use_internal_fn for
	calls with an lhs.
	* opts.c (default_options_table): Enable -ftree-builtin-call-cdce
	at -O and above.

From-SVN: r230488

gcc/ChangeLog

 2015-11-17  Richard Sandiford  <richard.sandiford@arm.com>
 
+	* builtins.c (expand_errno_check, expand_builtin_mathfn)
+	(expand_builtin_mathfn_2): Delete.
+	(expand_builtin): Remove handling of functions with
+	internal function equivalents.
+	* internal-fn.def (SET_EDOM): New internal function.
+	* internal-fn.h (set_edom_supported_p): Declare.
+	* internal-fn.c (expand_SET_EDOM): New function.
+	(set_edom_supported_p): Likewise.
+	* tree-call-cdce.c: Include builtins.h and internal-fn.h.
+	Rewrite comment at head of file.
+	(is_call_dce_candidate): Rename to...
+	(can_test_argument_range): ...this.  Don't check gimple_call_lhs
+	or gimple_call_builtin_p here.
+	(edom_only_function): New function.
+	(shrink_wrap_one_built_in_call_with_conds): New function, split out
+	from...
+	(shrink_wrap_one_built_in_call): ...here.
+	(can_use_internal_fn, use_internal_fn): New functions.
+	(shrink_wrap_conditional_dead_built_in_calls): Call use_internal_fn
+	for calls that have an lhs.
+	(pass_call_cdce::gate): Remove optimize_function_for_speed_p check.
+	(pass_call_cdce::execute): Skip blocks that are optimized for size.
+	Check gimple_call_builtin_p here.  Use can_use_internal_fn for
+	calls with an lhs.
+	* opts.c (default_options_table): Enable -ftree-builtin-call-cdce
+	at -O and above.
+
+2015-11-17  Richard Sandiford  <richard.sandiford@arm.com>
+
 	* builtins.h (called_as_built_in): Declare.
 	* builtins.c (called_as_built_in): Make external.
 	* internal-fn.h (expand_internal_call): Define a variant that

gcc/internal-fn.c

@@ -2073,6 +2073,24 @@ expand_GOACC_REDUCTION (internal_fn, gcall *)
   gcc_unreachable ();
 }
 
+/* Set errno to EDOM.  */
+
+static void
+expand_SET_EDOM (internal_fn, gcall *)
+{
+#ifdef TARGET_EDOM
+#ifdef GEN_ERRNO_RTX
+  rtx errno_rtx = GEN_ERRNO_RTX;
+#else
+  rtx errno_rtx = gen_rtx_MEM (word_mode, gen_rtx_SYMBOL_REF (Pmode, "errno"));
+#endif
+  emit_move_insn (errno_rtx,
+		  gen_int_mode (TARGET_EDOM, GET_MODE (errno_rtx)));
+#else
+  gcc_unreachable ();
+#endif
+}
+
 /* Expand a call to FN using the operands in STMT.  FN has a single
    output operand and NARGS input operands.  */
 
@@ -2217,6 +2235,18 @@ direct_internal_fn_supported_p (internal_fn fn, tree type)
   return direct_internal_fn_supported_p (fn, tree_pair (type, type));
 }
 
+/* Return true if IFN_SET_EDOM is supported.  */
+
+bool
+set_edom_supported_p (void)
+{
+#ifdef TARGET_EDOM
+  return true;
+#else
+  return false;
+#endif
+}
+
 #define DEF_INTERNAL_OPTAB_FN(CODE, FLAGS, OPTAB, TYPE) \
   static void						\
   expand_##CODE (internal_fn fn, gcall *stmt)		\

gcc/internal-fn.def

@@ -181,6 +181,10 @@ DEF_INTERNAL_FN (GOACC_LOOP, ECF_PURE | ECF_NOTHROW, NULL)
 /* OpenACC reduction abstraction.  See internal-fn.h  for usage.  */
 DEF_INTERNAL_FN (GOACC_REDUCTION, ECF_NOTHROW | ECF_LEAF, NULL)
 
+/* Set errno to EDOM, if GCC knows how to do that directly for the
+   current target.  */
+DEF_INTERNAL_FN (SET_EDOM, ECF_LEAF | ECF_NOTHROW, NULL)
+
 #undef DEF_INTERNAL_INT_FN
 #undef DEF_INTERNAL_FLT_FN
 #undef DEF_INTERNAL_OPTAB_FN

gcc/internal-fn.h

@@ -160,6 +160,7 @@ extern tree_pair direct_internal_fn_types (internal_fn, tree, tree *);
 extern tree_pair direct_internal_fn_types (internal_fn, gcall *);
 extern bool direct_internal_fn_supported_p (internal_fn, tree_pair);
 extern bool direct_internal_fn_supported_p (internal_fn, tree);
+extern bool set_edom_supported_p (void);
 
 extern void expand_internal_call (gcall *);
 extern void expand_internal_call (internal_fn, gcall *);

gcc/opts.c

@@ -478,6 +478,7 @@ static const struct default_options default_options_table[] =
     { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fmove_loop_invariants, NULL, 1 },
     { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_ftree_pta, NULL, 1 },
     { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fssa_phiopt, NULL, 1 },
+    { OPT_LEVELS_1_PLUS, OPT_ftree_builtin_call_dce, NULL, 1 },
 
     /* -O2 optimizations.  */
     { OPT_LEVELS_2_PLUS, OPT_finline_small_functions, NULL, 1 },
@@ -503,7 +504,6 @@ static const struct default_options default_options_table[] =
       REORDER_BLOCKS_ALGORITHM_STC },
     { OPT_LEVELS_2_PLUS, OPT_freorder_functions, NULL, 1 },
     { OPT_LEVELS_2_PLUS, OPT_ftree_vrp, NULL, 1 },
-    { OPT_LEVELS_2_PLUS, OPT_ftree_builtin_call_dce, NULL, 1 },
     { OPT_LEVELS_2_PLUS, OPT_ftree_pre, NULL, 1 },
     { OPT_LEVELS_2_PLUS, OPT_ftree_switch_conversion, NULL, 1 },
     { OPT_LEVELS_2_PLUS, OPT_fipa_cp, NULL, 1 },