glsl: Add 64-bit integer support for constant expressions

This just adds the new operations and add 64-bit integer support to all
the existing cases where it is needed.

v2: fix some issues found in testing.
v2.1: add unreachable (Ian), add missing int/uint pack/unpack (Dave).

v3 (idr): Rebase on top of idr's series to generate
ir_expression_operation_constant.h. In addition, this version:

    Adds missing support for ir_unop_bit_not, ir_binop_all_equal,
    ir_binop_any_nequal, ir_binop_vector_extract,
    ir_triop_vector_insert, and ir_quadop_vector.

    Removes support for uint64_t from ir_unop_abs and ir_unop_sign.

v4 (idr): "cut them down later" => Remove ir_unop_b2u64 and
ir_unop_u642b.  Handle these with extra i2u or u2i casts just like
uint(bool) and bool(uint) conversion is done.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com> [v2]
Reviewed-by: Matt Turner <mattst88@gmail.com> [v3]
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>

src/compiler/glsl/ir_constant_expression.cpp

@@ -88,6 +88,42 @@ bitcast_f2u(float f)
    return u;
 }
 
+static double
+bitcast_u642d(uint64_t u)
+{
+   assert(sizeof(double) == sizeof(uint64_t));
+   double d;
+   memcpy(&d, &u, sizeof(d));
+   return d;
+}
+
+static double
+bitcast_i642d(int64_t i)
+{
+   assert(sizeof(double) == sizeof(int64_t));
+   double d;
+   memcpy(&d, &i, sizeof(d));
+   return d;
+}
+
+static double
+bitcast_d2u64(double d)
+{
+   assert(sizeof(double) == sizeof(uint64_t));
+   uint64_t u;
+   memcpy(&u, &d, sizeof(d));
+   return u;
+}
+
+static double
+bitcast_d2i64(double d)
+{
+   assert(sizeof(double) == sizeof(int64_t));
+   int64_t i;
+   memcpy(&i, &d, sizeof(d));
+   return i;
+}
+
 /**
  * Evaluate one component of a floating-point 4x8 unpacking function.
  */