Do not use constant names in generated code (#298)

* Do not use constant names in generated code

tsfc/fem.py

@@ -629,12 +629,7 @@ def callback(entity_id):
 
 @translate.register(TSFCConstantMixin)
 def translate_constant_value(terminal, mt, ctx):
-    value_size = numpy.prod(terminal.ufl_shape, dtype=int)
-    expression = gem.reshape(
-        gem.Variable(terminal.name, (value_size,)),
-        terminal.ufl_shape
-    )
-    return expression
+    return ctx.constant(terminal)
 
 
 @translate.register(Coefficient)

tsfc/kernel_interface/__init__.py

@@ -17,6 +17,10 @@ def coefficient(self, ufl_coefficient, restriction):
         """A function that maps :class:`ufl.Coefficient`s to GEM
         expressions."""
 
+    @abstractmethod
+    def constant(self, const):
+        """Return the GEM expression corresponding to the constant."""
+
     @abstractmethod
     def cell_orientation(self, restriction):
         """Cell orientation as a GEM expression."""

tsfc/kernel_interface/common.py

@@ -68,6 +68,9 @@ def coefficient(self, ufl_coefficient, restriction):
         else:
             return kernel_arg[{'+': 0, '-': 1}[restriction]]
 
+    def constant(self, const):
+        return self.constant_map[const]
+
     def cell_orientation(self, restriction):
         """Cell orientation as a GEM expression."""
         f = {None: 0, '+': 0, '-': 1}[restriction]
@@ -435,16 +438,17 @@ def check_requirements(ir):
     return cell_orientations, cell_sizes, tuple(sorted(rt_tabs.items()))
 
 
-def prepare_constant(constant):
+def prepare_constant(constant, number):
     """Bridges the kernel interface and the GEM abstraction for
     Constants.
 
     :arg constant: Firedrake Constant
+    :arg number: Value to uniquely identify the constant
     :returns: (funarg, expression)
          expression - GEM expression referring to the Constant value(s)
     """
     value_size = numpy.prod(constant.ufl_shape, dtype=int)
-    return gem.reshape(gem.Variable(constant.name, (value_size,)),
+    return gem.reshape(gem.Variable(f"c_{number}", (value_size,)),
                        constant.ufl_shape)
 
 

tsfc/kernel_interface/firedrake_loopy.py

@@ -173,8 +173,8 @@ def set_coefficients(self, coefficients):
                 self._coefficient(coefficient, f"w_{i}")
 
     def set_constants(self, constants):
-        for const in constants:
-            gemexpr = prepare_constant(const)
+        for i, const in enumerate(constants):
+            gemexpr = prepare_constant(const, i)
             self.constant_map[const] = gemexpr
 
     def set_coefficient_numbers(self, coefficient_numbers):
@@ -334,8 +334,8 @@ def set_coefficients(self, integral_data, form_data):
                 n += 1
 
     def set_constants(self, constants):
-        for const in constants:
-            gemexpr = prepare_constant(const)
+        for i, const in enumerate(constants):
+            gemexpr = prepare_constant(const, i)
             self.constant_map[const] = gemexpr
 
     def register_requirements(self, ir):