rtl: builtins: (not just) rs6000: Add builtins for fegetround, feclearexcept and feraiseexcept [PR94193]

This optimizations were originally in glibc, but was removed
and suggested that they were a good fit as gcc builtins[1].

feclearexcept and feraiseexcept were extended (in comparison to the
glibc version) to accept any combination of the accepted flags, not
limited to just one flag bit at a time anymore.

The builtin expanders needs knowledge of the target libc's FE_*
values, so they are limited to expand only to suitable libcs.

[1] https://sourceware.org/legacy-ml/libc-alpha/2020-03/msg00047.html
    https://sourceware.org/legacy-ml/libc-alpha/2020-03/msg00080.html

2020-08-13  Raoni Fassina Firmino  <raoni@linux.ibm.com>

gcc/
	PR target/94193
	* builtins.cc (expand_builtin_fegetround): New function.
	(expand_builtin_feclear_feraise_except): New function.
	(expand_builtin): Add cases for BUILT_IN_FEGETROUND,
	BUILT_IN_FECLEAREXCEPT and BUILT_IN_FERAISEEXCEPT.
	* config/rs6000/rs6000.md (fegetroundsi): New pattern.
	(feclearexceptsi): New Pattern.
	(feraiseexceptsi): New Pattern.
	* doc/extend.texi: Add a new introductory paragraph about the
	new builtins.
	* doc/md.texi: (fegetround@var{m}): Document new optab.
	(feclearexcept@var{m}): Document new optab.
	(feraiseexcept@var{m}): Document new optab.
	* optabs.def (fegetround_optab): New optab.
	(feclearexcept_optab): New optab.
	(feraiseexcept_optab): New optab.

gcc/testsuite/
	PR target/94193
	* gcc.target/powerpc/builtin-feclearexcept-feraiseexcept-1.c: New test.
	* gcc.target/powerpc/builtin-feclearexcept-feraiseexcept-2.c: New test.
	* gcc.target/powerpc/builtin-fegetround.c: New test.

Signed-off-by: Raoni Fassina Firmino <raoni@linux.ibm.com>

1 files changed, 76 insertions, 0 deletions

diff --git a/gcc/builtins.cc b/gcc/builtins.cc
index bf07341..e842080 100644
--- a/gcc/builtins.cc
+++ b/gcc/builtins.cc
@@ -119,6 +119,9 @@ static rtx expand_builtin_mathfn_3 (tree, rtx, rtx);
 static rtx expand_builtin_mathfn_ternary (tree, rtx, rtx);
 static rtx expand_builtin_interclass_mathfn (tree, rtx);
 static rtx expand_builtin_sincos (tree);
+static rtx expand_builtin_fegetround (tree, rtx, machine_mode);
+static rtx expand_builtin_feclear_feraise_except (tree, rtx, machine_mode,
+						  optab);
 static rtx expand_builtin_cexpi (tree, rtx);
 static rtx expand_builtin_int_roundingfn (tree, rtx);
 static rtx expand_builtin_int_roundingfn_2 (tree, rtx);
@@ -2555,6 +2558,59 @@ expand_builtin_sincos (tree exp)
   return const0_rtx;
 }
 
+/* Expand call EXP to the fegetround builtin (from C99 fenv.h), returning the
+   result and setting it in TARGET.  Otherwise return NULL_RTX on failure.  */
+static rtx
+expand_builtin_fegetround (tree exp, rtx target, machine_mode target_mode)
+{
+  if (!validate_arglist (exp, VOID_TYPE))
+    return NULL_RTX;
+
+  insn_code icode = direct_optab_handler (fegetround_optab, SImode);
+  if (icode == CODE_FOR_nothing)
+    return NULL_RTX;
+
+  if (target == 0
+      || GET_MODE (target) != target_mode
+      || !(*insn_data[icode].operand[0].predicate) (target, target_mode))
+    target = gen_reg_rtx (target_mode);
+
+  rtx pat = GEN_FCN (icode) (target);
+  if (!pat)
+    return NULL_RTX;
+  emit_insn (pat);
+
+  return target;
+}
+
+/* Expand call EXP to either feclearexcept or feraiseexcept builtins (from C99
+   fenv.h), returning the result and setting it in TARGET.  Otherwise return
+   NULL_RTX on failure.  */
+static rtx
+expand_builtin_feclear_feraise_except (tree exp, rtx target,
+				       machine_mode target_mode, optab op_optab)
+{
+  if (!validate_arglist (exp, INTEGER_TYPE, VOID_TYPE))
+    return NULL_RTX;
+  rtx op0 = expand_normal (CALL_EXPR_ARG (exp, 0));
+
+  insn_code icode = direct_optab_handler (op_optab, SImode);
+  if (icode == CODE_FOR_nothing)
+    return NULL_RTX;
+
+  if (target == 0
+      || GET_MODE (target) != target_mode
+      || !(*insn_data[icode].operand[0].predicate) (target, target_mode))
+    target = gen_reg_rtx (target_mode);
+
+  rtx pat = GEN_FCN (icode) (target, op0);
+  if (!pat)
+    return NULL_RTX;
+  emit_insn (pat);
+
+  return target;
+}
+
 /* Expand a call to the internal cexpi builtin to the sincos math function.
    EXP is the expression that is a call to the builtin function; if convenient,
    the result should be placed in TARGET.  */
@@ -7056,6 +7112,26 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
 	return target;
       break;
 
+    case BUILT_IN_FEGETROUND:
+      target = expand_builtin_fegetround (exp, target, target_mode);
+      if (target)
+	return target;
+      break;
+
+    case BUILT_IN_FECLEAREXCEPT:
+      target = expand_builtin_feclear_feraise_except (exp, target, target_mode,
+						      feclearexcept_optab);
+      if (target)
+	return target;
+      break;
+
+    case BUILT_IN_FERAISEEXCEPT:
+      target = expand_builtin_feclear_feraise_except (exp, target, target_mode,
+						      feraiseexcept_optab);
+      if (target)
+	return target;
+      break;
+
     case BUILT_IN_APPLY_ARGS:
       return expand_builtin_apply_args ();