[GCC][PATCH][mid-end][Version 3] Optimize x * copysign (1.0, y) [Patch (1/2)]

[Tamar Christina <tamar dot christina at arm dot com>]

Hi All,

this patch implements a optimization rewriting

x * copysign (1.0, y)

to:

x ^ (y & (1 << sign_bit_position))


This is only done when not honoring signaling NaNs.
This transormation is done at ssa mult widening time and
is gated on the a check for the optab "xorsign".
If the optab is not available then copysign is expanded as normal.

If the optab exists then the expression is replaced with
a call to the internal function XORSIGN.

This patch is a revival of a previous patches
https://gcc.gnu.org/ml/gcc-patches/2015-10/msg00069.html
https://gcc.gnu.org/ml/gcc-patches/2017-06/msg00749.html

Bootstrapped on both aarch64-none-linux-gnu and x86_64 with no issues.
Regression done on aarch64-none-linux-gnu and no regressions.

Ok for trunk?

gcc/
2017-08-03  Tamar Christina  <tamar.christina@arm.com>
	    Andrew Pinski <pinskia@gmail.com>

	PR middle-end/19706
	* internal-fn.def (XORSIGN): New.
	* optabs.def (xorsign_optab): New.
	* tree-ssa-math-opts.c (is_copysign_call_with_1): New.
	(convert_expand_mult_copysign): New.
	(pass_optimize_widening_mul::execute): Call convert_expand_mult_copysign.

-- 

diff --git a/gcc/internal-fn.def b/gcc/internal-fn.def
index a9a3f7606eb2a79f64dab1b7fdeef0d308e3061d..58e5f4a322a92ccb842ab05cc4213933ffa59679 100644
--- a/gcc/internal-fn.def
+++ b/gcc/internal-fn.def
@@ -129,6 +129,8 @@ DEF_INTERNAL_FLT_FN (REMAINDER, ECF_CONST, remainder, binary)
 DEF_INTERNAL_FLT_FN (SCALB, ECF_CONST, scalb, binary)
 DEF_INTERNAL_FLT_FN (FMIN, ECF_CONST, fmin, binary)
 DEF_INTERNAL_FLT_FN (FMAX, ECF_CONST, fmax, binary)
+DEF_INTERNAL_OPTAB_FN (XORSIGN, ECF_CONST, xorsign, binary)
+
 
 /* FP scales.  */
 DEF_INTERNAL_FLT_FN (LDEXP, ECF_CONST, ldexp, binary)
diff --git a/gcc/optabs.def b/gcc/optabs.def
index f21f2267ec2118d5cd0e74b18721525a564d16f2..54afe2d796ee9af3bd7b25d93eb0789a70e47c7b 100644
--- a/gcc/optabs.def
+++ b/gcc/optabs.def
@@ -255,6 +255,7 @@ OPTAB_D (asin_optab, "asin$a2")
 OPTAB_D (atan2_optab, "atan2$a3")
 OPTAB_D (atan_optab, "atan$a2")
 OPTAB_D (copysign_optab, "copysign$F$a3")
+OPTAB_D (xorsign_optab, "xorsign$F$a3")
 OPTAB_D (cos_optab, "cos$a2")
 OPTAB_D (exp10_optab, "exp10$a2")
 OPTAB_D (exp2_optab, "exp2$a2")
diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
index 7ac1659fa0670b7080685f3f9513939807073a63..780a7f76ce756cfe025e80845208b00568eda56c 100644
--- a/gcc/tree-ssa-math-opts.c
+++ b/gcc/tree-ssa-math-opts.c
@@ -3145,6 +3145,96 @@ is_widening_mult_p (gimple *stmt,
   return true;
 }
 
+/* Check to see if the CALL statement is an invocation of copysign
+   with 1. being the first argument.  */
+static bool
+is_copysign_call_with_1 (gimple *call)
+{
+  if (!is_gimple_call (call))
+    return false;
+
+  enum combined_fn code = gimple_call_combined_fn (call);
+
+  if (code == CFN_LAST)
+    return false;
+
+  gcall *c = as_a<gcall*> (call);
+
+  if (builtin_fn_p (code))
+    {
+      switch (as_builtin_fn (code))
+	{
+	CASE_FLT_FN (BUILT_IN_COPYSIGN):
+	CASE_FLT_FN_FLOATN_NX (BUILT_IN_COPYSIGN):
+	  return real_onep (gimple_call_arg (c, 0));
+	default:
+	  return false;
+	}
+    }
+
+  if (internal_fn_p (code))
+    {
+      switch (as_internal_fn (code))
+	{
+	case IFN_COPYSIGN:
+	  return real_onep (gimple_call_arg (c, 0));
+	default:
+	  return false;
+	}
+    }
+
+   return false;
+}
+
+/* Try to expand the pattern x * copysign (1, y) into xorsign (x, y).
+   This only happens when the the xorsign optab is defined, if the
+   pattern is not a xorsign pattern or if expansion fails FALSE is
+   returned, otherwise TRUE is returned.  */
+static bool
+convert_expand_mult_copysign (gimple *stmt, gimple_stmt_iterator *gsi)
+{
+  tree treeop0, treeop1, lhs, type;
+  location_t loc = gimple_location (stmt);
+  lhs = gimple_assign_lhs (stmt);
+  treeop0 = gimple_assign_rhs1 (stmt);
+  treeop1 = gimple_assign_rhs2 (stmt);
+  type = TREE_TYPE (lhs);
+  machine_mode mode = TYPE_MODE (type);
+
+  if (HONOR_SNANS (type))
+    return false;
+
+  if (TREE_CODE (treeop0) == SSA_NAME && TREE_CODE (treeop1) == SSA_NAME)
+    {
+      gimple *call0 = SSA_NAME_DEF_STMT (treeop0);
+      if (!is_copysign_call_with_1 (call0))
+	{
+	  /* IPA sometimes inlines and then extracts the function again,
+	     resulting in an incorrect order, so check both ways.  */
+	  call0 = SSA_NAME_DEF_STMT (treeop1);
+	  if (!is_copysign_call_with_1 (call0))
+	    return false;
+
+	  treeop1 = treeop0;
+	}
+
+	if (optab_handler (xorsign_optab, mode) == CODE_FOR_nothing)
+	  return false;
+
+	gcall *c = as_a<gcall*> (call0);
+	treeop0 = gimple_call_arg (c, 1);
+
+	gcall *call_stmt
+	  = gimple_build_call_internal (IFN_XORSIGN, 2, treeop1,treeop0);
+	gimple_set_lhs (call_stmt, lhs);
+	gimple_set_location (call_stmt, loc);
+	gsi_insert_after (gsi, call_stmt, GSI_SAME_STMT);
+	return true;
+    }
+
+  return false;
+}
+
 /* Process a single gimple statement STMT, which has a MULT_EXPR as
    its rhs, and try to convert it into a WIDEN_MULT_EXPR.  The return
    value is true iff we converted the statement.  */
@@ -4122,6 +4212,11 @@ pass_optimize_widening_mul::execute (function *fun)
 		      release_defs (stmt);
 		      continue;
 		    }
+		 if (convert_expand_mult_copysign (stmt, &gsi))
+		    {
+		      gsi_remove (&gsi, true);
+		      continue;
+		    }
 		  break;
 
 		case PLUS_EXPR: