source/opt/unify_const_pass.h

// Copyright (c) 2016 Google Inc.
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#ifndef LIBSPIRV_OPT_UNIFY_CONSTANT_PASS_H_
#define LIBSPIRV_OPT_UNIFY_CONSTANT_PASS_H_

#include "module.h"
#include "pass.h"

namespace spvtools {
namespace opt {

// The optimization pass to de-duplicate the constants. Constants with exactly
// same values and identical form will be unified and only one constant will be
// kept for each unique pair of type and value.
// There are several cases not handled by this pass:
//  1) Constants defined by OpConstantNull instructions (null constants) and
//  constants defined by OpConstantFalse, OpConstant or OpConstantComposite
//  with value(s) 0 (zero-valued normal constants) are not considered
//  equivalent. So null constants won't be used to replace zero-valued normal
//  constants, and other constants won't replace the null constants either.
//  2) Whenever there are decorations to the constant's result id or its type
//  id, the constants won't be handled, which means, it won't be used to
//  replace any other constants, neither can other constants replace it.
//  3) NaN in float point format with different bit patterns are not unified.
class UnifyConstantPass : public Pass {
 public:
  const char* name() const override { return "unify-const"; }
  bool Process(ir::Module*) override;
};

}  // namespace opt
}  // namespace spvtools

#endif // LIBSPIRV_OPT_UNIFY_CONSTANT_PASS_H_