[PATCH, rs6000] Gimple folding of splat_uX

[Will Schmidt]

Hi,
Add support for gimple folding of splat_u{8,16,32}.
Testcase coverage is primarily handled by existing tests
testsuite/gcc.target/powerpc/fold-vec-splat_*.c
    
One new test added to verify we continue to receive
an 'invalid argument, must be a 5-bit immediate' error
when we try to splat a non-constant value.
    
Regtests currently running across assorted power systems.
OK for trunk with successful results?
   
Thanks
-Will
    
[gcc]

2017-12-05  Will Schmidt  <will_schm...@vnet.ibm.com>
    
        * config/rs6000/rs6000.c (rs6000_gimple_fold_builtin): Add support for
        early folding of splat_u{8,16,32}.
    
[testsuite]

2017-12-05  Will Schmidt  <will_schm...@vnet.ibm.com>

        * gcc.target/powerpc/fold-vec-splat-misc-invalid.c: New.

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 045a014..1470557 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -16614,10 +16614,33 @@ rs6000_gimple_fold_builtin (gimple_stmt_iterator *gsi)
     case VSX_BUILTIN_CMPLE_2DI:
     case VSX_BUILTIN_CMPLE_U2DI:
       fold_compare_helper (gsi, LE_EXPR, stmt);
       return true;
 
+    /* flavors of vec_splat_[us]{8,16,32}.  */
+    case ALTIVEC_BUILTIN_VSPLTISB:
+    case ALTIVEC_BUILTIN_VSPLTISH:
+    case ALTIVEC_BUILTIN_VSPLTISW:
+      {
+        arg0 = gimple_call_arg (stmt, 0);
+        lhs = gimple_call_lhs (stmt);
+        /* Only fold the vec_splat_*() if arg0 is constant.  */
+        if ( TREE_CODE (arg0) != INTEGER_CST)
+          return false;
+        tree splat_value = build_int_cst (TREE_TYPE (TREE_TYPE (lhs)),
+                                          TREE_INT_CST_LOW (arg0));
+        vec<constructor_elt, va_gc> *ctor_elts = NULL;
+        unsigned int n_elts = TYPE_VECTOR_SUBPARTS (TREE_TYPE (lhs));
+        for (unsigned int i=0; i < n_elts ; i++)
+          CONSTRUCTOR_APPEND_ELT (ctor_elts, NULL_TREE, splat_value);
+        tree splat_tree = build_constructor (TREE_TYPE (lhs), ctor_elts);
+        g = gimple_build_assign (lhs, splat_tree);
+        gimple_set_location (g, gimple_location (stmt));
+        gsi_replace (gsi, g, true);
+        return true;
+      }
+
     default:
       if (TARGET_DEBUG_BUILTIN)
        fprintf (stderr, "gimple builtin intrinsic not matched:%d %s %s\n",
                 fn_code, fn_name1, fn_name2);
       break;
diff --git a/gcc/testsuite/gcc.target/powerpc/fold-vec-splat-misc-invalid.c 
b/gcc/testsuite/gcc.target/powerpc/fold-vec-splat-misc-invalid.c
new file mode 100644
index 0000000..20f5b05
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/fold-vec-splat-misc-invalid.c
@@ -0,0 +1,33 @@
+/* Verify that overloaded built-ins for vec_splat_s8 and vec_splat_s16
+   generate errors as expected when we attempt to use invalid inputs.  */
+
+/* { dg-do compile } */
+/* { dg-require-effective-target powerpc_vsx_ok } */
+/* { dg-options "-mvsx -O2" } */
+
+#include <altivec.h>
+
+vector signed short
+testss_1 (unsigned int ui)
+{
+  return vec_splat_s16 (ui);/* { dg-error "argument 1 must be a 5-bit signed 
literal" } */
+}
+
+vector unsigned short
+testss_2 (signed int si)
+{
+  return vec_splat_u16 (si);/* { dg-error "argument 1 must be a 5-bit signed 
literal" } */
+}
+
+vector signed char
+testsc_1 (unsigned int ui)
+{
+  return vec_splat_s8 (ui); /* { dg-error "argument 1 must be a 5-bit signed 
literal" } */
+}
+
+vector unsigned char
+testsc_2 (signed int si)
+{
+  return vec_splat_u8 (si);/* { dg-error "argument 1 must be a 5-bit signed 
literal" } */
+}
+