[PATCH] Handle __builtin_bswap{16,32,64} in bitwise ccp (PR tree-optimization/89475)

[Richard Biener]

On February 24, 2019 12:58:05 PM GMT+01:00, Jakub Jelinek <jakub@redhat.com> wrote:
>Hi!
>
>These builtins are perfect candidates for bitwise ccp, the bytes are
>preserved, just byte-swapped.
>
>Noticed this while wondering why we haven't optimized the f9 function
>in another PR, bswap64 zero extended from 32-bits, later casted to
>32-bit
>unsigned int is 0.
>
>Bootstrapped/regtested on x86_64-linux and i686-linux, ok for GCC10?

OK. 

Richard. 

>2019-02-23  Jakub Jelinek  <jakub@redhat.com>
>
>	PR tree-optimization/89475
>	* tree-ssa-ccp.c (evaluate_stmt): Handle BUILT_IN_BSWAP{16,32,64}
>	calls.
>
>	* gcc.dg/tree-ssa/pr89475.c: New test.
>
>--- gcc/tree-ssa-ccp.c.jj	2019-01-01 12:37:17.078976247 +0100
>+++ gcc/tree-ssa-ccp.c	2019-02-23 22:35:23.888343273 +0100
>@@ -1960,6 +1960,35 @@ evaluate_stmt (gimple *stmt)
> 		break;
> 	      }
> 
>+	    case BUILT_IN_BSWAP16:
>+	    case BUILT_IN_BSWAP32:
>+	    case BUILT_IN_BSWAP64:
>+	      val = get_value_for_expr (gimple_call_arg (stmt, 0), true);
>+	      if (val.lattice_val == UNDEFINED)
>+		break;
>+	      else if (val.lattice_val == CONSTANT
>+		       && val.value
>+		       && TREE_CODE (val.value) == INTEGER_CST)
>+		{
>+		  tree type = TREE_TYPE (gimple_call_lhs (stmt));
>+		  int prec = TYPE_PRECISION (type);
>+		  wide_int wval = wi::to_wide (val.value);
>+		  val.value
>+		    = wide_int_to_tree (type,
>+					wide_int::from (wval, prec,
>+							UNSIGNED).bswap ());
>+		  val.mask
>+		    = widest_int::from (wide_int::from (val.mask, prec,
>+							UNSIGNED).bswap (),
>+					UNSIGNED);
>+		  if (wi::sext (val.mask, prec) != -1)
>+		    break;
>+		}
>+	      val.lattice_val = VARYING;
>+	      val.value = NULL_TREE;
>+	      val.mask = -1;
>+	      break;
>+
> 	    default:;
> 	    }
> 	}
>--- gcc/testsuite/gcc.dg/tree-ssa/pr89475.c.jj	2019-02-23
>18:58:23.035845645 +0100
>+++ gcc/testsuite/gcc.dg/tree-ssa/pr89475.c	2019-02-23
>18:59:38.462607598 +0100
>@@ -0,0 +1,104 @@
>+/* PR tree-optimization/89475 */
>+/* { dg-do compile { target { ilp32 || lp64 } } } */
>+/* { dg-options "-O2 -fdump-tree-optimized" } */
>+/* { dg-final { scan-tree-dump-not "link_error " "optimized" } } */
>+
>+void link_error (void);
>+
>+unsigned short
>+f0 (unsigned short x)
>+{
>+  x &= 0xaa55;
>+  x = __builtin_bswap16 (x);
>+  if (x & 0xaa55)
>+    link_error ();
>+  return x;
>+}
>+
>+unsigned short
>+f1 (unsigned short x)
>+{
>+  x &= 0x55aa;
>+  x = __builtin_bswap16 (x);
>+  if (x & 0x55aa)
>+    link_error ();
>+  return x;
>+}
>+
>+unsigned int
>+f2 (unsigned int x)
>+{
>+  x &= 0x55aa5aa5U;
>+  x = __builtin_bswap32 (x);
>+  if (x & 0x5aa555aaU)
>+    link_error ();
>+  return x;
>+}
>+
>+unsigned long long int
>+f3 (unsigned long long int x)
>+{
>+  x &= 0x55aa5aa544cc2211ULL;
>+  x = __builtin_bswap64 (x);
>+  if (x & 0xeedd33bb5aa555aaULL)
>+    link_error ();
>+  return x;
>+}
>+
>+unsigned short
>+f4 (unsigned short x)
>+{
>+  x = __builtin_bswap32 (x);
>+  if (x != 0)
>+    link_error ();
>+  return x;
>+}
>+
>+unsigned int
>+f5 (unsigned int x)
>+{
>+  x = __builtin_bswap64 (x);
>+  if (x != 0)
>+    link_error ();
>+  return x;
>+}
>+
>+unsigned short
>+f6 (unsigned short x)
>+{
>+  x |= 0xaa55;
>+  x = __builtin_bswap16 (x);
>+  if ((x | 0xaa55) != 0xffff)
>+    link_error ();
>+  return x;
>+}
>+
>+unsigned short
>+f7 (unsigned short x)
>+{
>+  x |= 0x55aa;
>+  x = __builtin_bswap16 (x);
>+  if ((x | 0x55aa) != 0xffff)
>+    link_error ();
>+  return x;
>+}
>+
>+unsigned int
>+f8 (unsigned int x)
>+{
>+  x |= 0x55aa5aa5U;
>+  x = __builtin_bswap32 (x);
>+  if ((x | 0x5aa555aaU) != 0xffffffffU)
>+    link_error ();
>+  return x;
>+}
>+
>+unsigned long long int
>+f9 (unsigned long long int x)
>+{
>+  x |= 0x55aa5aa544cc2211ULL;
>+  x = __builtin_bswap64 (x);
>+  if ((x | 0xeedd33bb5aa555aaULL) != 0xffffffffffffffffULL)
>+    link_error ();
>+  return x;
>+}
>
>	Jakub