i386.c (ix86_emit_swsqrtsf): Filter out infinity result of rsqrt insn for zero input...

        * config/i386/i386.c (ix86_emit_swsqrtsf): Filter out infinity
        result of rsqrt insn for zero input argument to avoid NaN.

From-SVN: r125858

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2c19891b6ddb4d0bd15d0d0aab92ea46d0fce484..32754f56f595860f271f0311750dd1ab7459f55b 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -106,8 +106,8 @@
 
 2007-06-19  Uros Bizjak  <ubizjak@gmail.com>
 
-       * config/i386/i386.c (ix86_emit_swsqrtsf): Limit the result of
-       rsqrt insn to FLT_MAX to avoid NaN for zero input argument.
+       * config/i386/i386.c (ix86_emit_swsqrtsf): Filter out infinity
+       result of rsqrt insn for zero input argument to avoid NaN.
 
 2007-06-19  Richard Guenther  <rguenther@suse.de>
 

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 204373c82ba4c40efdf3c57cc37c25c57797eb4b..1a8fa110927c1ebb5cd579c6563e55fd02499e71 100644 (file)
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -22593,7 +22593,7 @@ void ix86_emit_swdivsf (rtx res, rtx a, rtx b, enum machine_mode mode)
 void ix86_emit_swsqrtsf (rtx res, rtx a, enum machine_mode mode,
                         bool recip)
 {
-  rtx x0, e0, e1, e2, e3, three, half, bignum;
+  rtx x0, e0, e1, e2, e3, three, half, zero, mask;
 
   x0 = gen_reg_rtx (mode);
   e0 = gen_reg_rtx (mode);
@@ -22603,29 +22603,41 @@ void ix86_emit_swsqrtsf (rtx res, rtx a, enum machine_mode mode,
 
   three = CONST_DOUBLE_FROM_REAL_VALUE (dconst3, SFmode);
   half = CONST_DOUBLE_FROM_REAL_VALUE (dconsthalf, SFmode);
-  bignum = gen_lowpart (SFmode, GEN_INT (0x7f7fffff));
+
+  mask = gen_reg_rtx (mode);
 
   if (VECTOR_MODE_P (mode))
     {
       three = ix86_build_const_vector (SFmode, true, three);
       half = ix86_build_const_vector (SFmode, true, half);
-      bignum = ix86_build_const_vector (SFmode, true, bignum);
     }
 
   three = force_reg (mode, three);
   half = force_reg (mode, half);
-  bignum = force_reg (mode, bignum);
+
+  zero = force_reg (mode, CONST0_RTX(mode));
 
   /* sqrt(a) = 0.5 * a * rsqrtss(a) * (3.0 - a * rsqrtss(a) * rsqrtss(a))
      1.0 / sqrt(a) = 0.5 * rsqrtss(a) * (3.0 - a * rsqrtss(a) * rsqrtss(a)) */
 
+  /* Compare a to zero.  */
+  emit_insn (gen_rtx_SET (VOIDmode, mask,
+                         gen_rtx_NE (mode, a, zero)));
+
   /* x0 = 1./sqrt(a) estimate */
   emit_insn (gen_rtx_SET (VOIDmode, x0,
                          gen_rtx_UNSPEC (mode, gen_rtvec (1, a),
                                          UNSPEC_RSQRT)));
-  emit_insn (gen_rtx_SET (VOIDmode, x0,
-                         gen_rtx_SMIN (mode, x0, bignum)));
- 
+  /* Filter out infinity.  */
+  if (VECTOR_MODE_P (mode))
+    emit_insn (gen_rtx_SET (VOIDmode, gen_lowpart (V4SFmode, x0),
+                           gen_rtx_AND (mode,
+                                        gen_lowpart (V4SFmode, x0),
+                                        gen_lowpart (V4SFmode, mask))));
+  else
+    emit_insn (gen_rtx_SET (VOIDmode, x0,
+                           gen_rtx_AND (mode, x0, mask)));
+
   /* e0 = x0 * a */
   emit_insn (gen_rtx_SET (VOIDmode, e0,
                          gen_rtx_MULT (mode, x0, a)));