Improve factor_out_conditional_operation for conversions and constants

In the case of a NOP conversion (precisions of the 2 types are equal),
factoring out the conversion can be done even if int_fits_type_p returns
false and even when the conversion is defined by a statement inside the
conditional. Since it is a NOP conversion there is no zero/sign extending
happening which is why it is ok to be done here; we were trying to prevent
an extra sign/zero extend from being moved away from definition which no-op
conversions are not.

Bootstrapped and tested on x86_64-linux-gnu with no regressions.

gcc/ChangeLog:

	PR tree-optimization/104376
	PR tree-optimization/101541
	* tree-ssa-phiopt.cc (factor_out_conditional_operation):
	Allow nop conversions even if it is defined by a statement
	inside the conditional.

gcc/testsuite/ChangeLog:

	PR tree-optimization/101541
	* gcc.dg/tree-ssa/phi-opt-39.c: New test.

2 files changed, 56 insertions, 3 deletions

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-39.c b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-39.c
new file mode 100644
index 0000000..6b6006a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-39.c
@@ -0,0 +1,43 @@
+/* { dg-options "-O2 -fdump-tree-phiopt" } */
+
+unsigned f0(int A)
+{
+//     A == 0? A : -A    same as -A
+  if (A == 0)  return A;
+  return -A;
+}
+
+unsigned f1(int A)
+{
+//     A != 0? A : -A    same as A
+  if (A != 0)  return A;
+  return -A;
+}
+unsigned f2(int A)
+{
+//     A >= 0? A : -A    same as abs (A)
+  if (A >= 0)  return A;
+  return -A;
+}
+unsigned f3(int A)
+{
+//     A > 0?  A : -A    same as abs (A)
+  if (A > 0)  return A;
+  return -A;
+}
+unsigned f4(int A)
+{
+//     A <= 0? A : -A    same as -abs (A)
+  if (A <= 0)  return A;
+  return -A;
+}
+unsigned f5(int A)
+{
+//     A < 0?  A : -A    same as -abs (A)
+  if (A < 0)  return A;
+  return -A;
+}
+
+/* f4 and f5 are not allowed to be optimized in early phi-opt. */
+/* { dg-final { scan-tree-dump-times "if" 2 "phiopt1" } } */
+/* { dg-final { scan-tree-dump-not "if" "phiopt2" } } */
diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
index 312a6f9..bb55a4f 100644
--- a/gcc/tree-ssa-phiopt.cc
+++ b/gcc/tree-ssa-phiopt.cc
@@ -310,7 +310,9 @@ factor_out_conditional_operation (edge e0, edge e1, gphi *phi,
 	return NULL;
       /* If arg1 is an INTEGER_CST, fold it to new type.  */
       if (INTEGRAL_TYPE_P (TREE_TYPE (new_arg0))
-	  && int_fits_type_p (arg1, TREE_TYPE (new_arg0)))
+	  && (int_fits_type_p (arg1, TREE_TYPE (new_arg0))
+	      || (TYPE_PRECISION (TREE_TYPE (new_arg0))
+		   == TYPE_PRECISION (TREE_TYPE (arg1)))))
 	{
 	  if (gimple_assign_cast_p (arg0_def_stmt))
 	    {
@@ -322,8 +324,12 @@ factor_out_conditional_operation (edge e0, edge e1, gphi *phi,
 		 if arg0_def_stmt is the only non-debug stmt in
 		 its basic block, because then it is possible this
 		 could enable further optimizations (minmax replacement
-		 etc.).  See PR71016.  */
-	      if (new_arg0 != gimple_cond_lhs (cond_stmt)
+		 etc.).  See PR71016.
+		 Note no-op conversions don't have this issue as
+		 it will not generate any zero/sign extend in that case.  */
+	      if ((TYPE_PRECISION (TREE_TYPE (new_arg0))
+		    != TYPE_PRECISION (TREE_TYPE (arg1)))
+	          && new_arg0 != gimple_cond_lhs (cond_stmt)
 		  && new_arg0 != gimple_cond_rhs (cond_stmt)
 		  && gimple_bb (arg0_def_stmt) == e0->src)
 		{
@@ -354,6 +360,10 @@ factor_out_conditional_operation (edge e0, edge e1, gphi *phi,
 		    return NULL;
 		}
 	      new_arg1 = fold_convert (TREE_TYPE (new_arg0), arg1);
+
+	      /* Drop the overlow that fold_convert might add. */
+	      if (TREE_OVERFLOW (new_arg1))
+		new_arg1 = drop_tree_overflow (new_arg1);
 	    }
 	  else
 	    return NULL;