optabs.c (prepare_float_lib_cmp): Attach a REG_EQUAL note describing the return value...

	* optabs.c (prepare_float_lib_cmp):  Attach a REG_EQUAL note
	describing the return value of the comparison libcall to the
	REG_RETVAL instruction of the emitted sequence.

From-SVN: r72148

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a0112d2ca75da3ca1cf694a5aa178177b2d2007c..4b4130637bcef27d9071bc5601fde64466bdbc8a 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2003-10-06  Roger Sayle  <roger@eyesopen.com>
+
+       * optabs.c (prepare_float_lib_cmp):  Attach a REG_EQUAL note
+       describing the return value of the comparison libcall to the
+       REG_RETVAL instruction of the emitted sequence.
+
 2003-10-06  Eric Botcazou  <ebotcazou@libertysurf.fr>
 
        PR optimization/12215

diff --git a/gcc/optabs.c b/gcc/optabs.c
index bd9306d4df130f41fe8b29ff29a2a54c80dfd386..7f8affc0ddf7aa08c05268b12df3d24426552d21 100644 (file)
--- a/gcc/optabs.c
+++ b/gcc/optabs.c
@@ -3877,6 +3877,7 @@ prepare_float_lib_cmp (rtx *px, rtx *py, enum rtx_code *pcomparison,
   rtx y = protect_from_queue (*py, 0);
   enum machine_mode orig_mode = GET_MODE (x);
   enum machine_mode mode;
+  rtx before_call;
   rtx libfunc = 0;
   rtx result;
 
@@ -3903,12 +3904,97 @@ prepare_float_lib_cmp (rtx *px, rtx *py, enum rtx_code *pcomparison,
       y = convert_to_mode (mode, y, 0);
     }
 
+  before_call = get_last_insn ();
+
+  result = emit_library_call_value (libfunc, NULL_RTX, LCT_CONST_MAKE_BLOCK,
+                                   word_mode, 2, x, mode, y, mode);
+
+  /* If we're optimizing attach a REG_EQUAL note describing the semantics
+     of the libcall to the RTL.  The allows the RTL optimizers to delete
+     the libcall if the condition can be determined at compile-time.  */
+  if (optimize
+      && ! side_effects_p (x)
+      && ! side_effects_p (y))
+    {
+      /* Search backwards through the insns emitted above looking for
+        the instruction with the REG_RETVAL note.  */
+      rtx last = get_last_insn ();
+      while (last != before_call)
+       {
+         if (find_reg_note (last, REG_RETVAL, NULL))
+           break;
+         last = PREV_INSN (last);
+       }
+
+      if (last != before_call)
+       {
+         rtx equiv;
+         if (comparison == UNORDERED)
+           {
+             rtx temp = simplify_gen_relational (NE, word_mode,
+                                                 mode, x, x);
+             equiv = simplify_gen_relational (NE, word_mode,
+                                              mode, y, y);
+             equiv = simplify_gen_ternary (IF_THEN_ELSE, word_mode,
+                                           word_mode, temp,
+                                           const_true_rtx, equiv);
+           }
+         else
+           {
+             equiv = simplify_gen_relational (comparison, word_mode,
+                                              mode, x, y);
+             if (! FLOAT_LIB_COMPARE_RETURNS_BOOL (mode, comparison))
+               {
+                 rtx true_rtx, false_rtx;
+
+                 switch (comparison)
+                   {
+                   case EQ:
+                     true_rtx = const0_rtx;
+                     false_rtx = const_true_rtx;
+                     break;
+
+                   case NE:
+                     true_rtx = const_true_rtx;
+                     false_rtx = const0_rtx;
+                     break;
+
+                   case GT:
+                     true_rtx = const1_rtx;
+                     false_rtx = const0_rtx;
+                     break;
+
+                   case GE:
+                     true_rtx = const0_rtx;
+                     false_rtx = constm1_rtx;
+                     break;
+
+                   case LT:
+                     true_rtx = constm1_rtx;
+                     false_rtx = const0_rtx;
+                     break;
+
+                   case LE:
+                     true_rtx = const0_rtx;
+                     false_rtx = const1_rtx;
+                     break;
+
+                   default:
+                     abort ();
+                   }
+                 equiv = simplify_gen_ternary (IF_THEN_ELSE, word_mode,
+                                               word_mode, equiv,
+                                               true_rtx, false_rtx);
+               }
+           }
+         set_unique_reg_note (last, REG_EQUAL, equiv);
+       }
+    }
+
   if (comparison == UNORDERED
       || FLOAT_LIB_COMPARE_RETURNS_BOOL (mode, comparison))
     comparison = NE;
 
-  result = emit_library_call_value (libfunc, NULL_RTX, LCT_CONST_MAKE_BLOCK,
-                                   word_mode, 2, x, mode, y, mode);
   *px = result;
   *py = const0_rtx;
   *pmode = word_mode;