Fix build for STORE_FLAG_VALUE<0 targets [PR118418]

In g:06c4cf398947b53b4bfc65752f9f879bb2d07924 I mishandled signed
comparisons of comparison results on STORE_FLAG_VALUE < 0 targets
(despite specifically referencing STORE_FLAG_VALUE in the commit
message).  There, (lt TRUE FALSE) is true, although (ltu FALSE TRUE)
still holds.

Things get messy with vector modes, and since those weren't the focus
of the original commit, it seemed better to punt on them for now.
However, punting means that this optimisation no longer feels like
a natural tail-call operation.  The patch therefore converts
"return simplify..." to the usual call-and-conditional-return pattern.

gcc/
	PR target/118418
	* simplify-rtx.cc (simplify_context::simplify_relational_operation_1):
	Take STORE_FLAG_VALUE into account when handling signed comparisons
	of comparison results.

diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
index 71c5d3c1b1b8bce1aa3ea31b06fa0315120db81b..dda8fc689e7935734b2369f1d299c386cdd870ee 100644 (file)
--- a/gcc/simplify-rtx.cc
+++ b/gcc/simplify-rtx.cc
@@ -6434,7 +6434,7 @@ simplify_context::simplify_relational_operation_1 (rtx_code code,
        return simplify_gen_binary (AND, mode, XEXP (tmp, 0), const1_rtx);
     }
 
-  /* For two booleans A and B:
+  /* For two unsigned booleans A and B:
 
      A >  B == ~B & A
      A >= B == ~B | A
@@ -6443,20 +6443,29 @@ simplify_context::simplify_relational_operation_1 (rtx_code code,
      A == B == ~A ^ B (== ~B ^ A)
      A != B ==  A ^ B
 
-     simplify_logical_relational_operation checks whether A and B
-     are booleans.  */
-  if (code == GTU || code == GT)
-    return simplify_logical_relational_operation (AND, mode, op1, op0, true);
-  if (code == GEU || code == GE)
-    return simplify_logical_relational_operation (IOR, mode, op1, op0, true);
-  if (code == LTU || code == LT)
-    return simplify_logical_relational_operation (AND, mode, op0, op1, true);
-  if (code == LEU || code == LE)
-    return simplify_logical_relational_operation (IOR, mode, op0, op1, true);
-  if (code == EQ)
-    return simplify_logical_relational_operation (XOR, mode, op0, op1, true);
-  if (code == NE)
-    return simplify_logical_relational_operation (XOR, mode, op0, op1);
+     For signed comparisons, we have to take STORE_FLAG_VALUE into account,
+     with the rules above applying for positive STORE_FLAG_VALUE and with
+     the relations reversed for negative STORE_FLAG_VALUE.  */
+  if (is_a<scalar_int_mode> (cmp_mode)
+      && COMPARISON_P (op0)
+      && COMPARISON_P (op1))
+    {
+      rtx t = NULL_RTX;
+      if (code == GTU || code == (STORE_FLAG_VALUE > 0 ? GT : LT))
+       t = simplify_logical_relational_operation (AND, mode, op1, op0, true);
+      else if (code == GEU || code == (STORE_FLAG_VALUE > 0 ? GE : LE))
+       t = simplify_logical_relational_operation (IOR, mode, op1, op0, true);
+      else if (code == LTU || code == (STORE_FLAG_VALUE > 0 ? LT : GT))
+       t = simplify_logical_relational_operation (AND, mode, op0, op1, true);
+      else if (code == LEU || code == (STORE_FLAG_VALUE > 0 ? LE : GE))
+       t = simplify_logical_relational_operation (IOR, mode, op0, op1, true);
+      else if (code == EQ)
+       t = simplify_logical_relational_operation (XOR, mode, op0, op1, true);
+      else if (code == NE)
+       t = simplify_logical_relational_operation (XOR, mode, op0, op1);
+      if (t)
+       return t;
+    }
 
   return NULL_RTX;
 }