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### 12.2 Class hierarchy of GIMPLE statements

The following diagram shows the C++ inheritance hierarchy of statement kinds, along with their relationships to `GSS_` values (layouts) and `GIMPLE_` values (codes):

            gimple
              |    layout: GSS_BASE
              |    used for 4 codes: GIMPLE_ERROR_MARK
              |                      GIMPLE_NOP
              |                      GIMPLE_OMP_SECTIONS_SWITCH
              |                      GIMPLE_PREDICT
              |
              + gimple_statement_with_ops_base
              |   |    (no GSS layout)
              |   |
              |   + gimple_statement_with_ops
              |   |   |    layout: GSS_WITH_OPS
              |   |   |
              |   |   + gcond
              |   |   |     code: GIMPLE_COND
              |   |   |
              |   |   + gdebug
              |   |   |     code: GIMPLE_DEBUG
              |   |   |
              |   |   + ggoto
              |   |   |     code: GIMPLE_GOTO
              |   |   |
              |   |   + glabel
              |   |   |     code: GIMPLE_LABEL
              |   |   |
              |   |   + gswitch
              |   |         code: GIMPLE_SWITCH
              |   |
              |   + gimple_statement_with_memory_ops_base
              |       |    layout: GSS_WITH_MEM_OPS_BASE
              |       |
              |       + gimple_statement_with_memory_ops
              |       |   |    layout: GSS_WITH_MEM_OPS
              |       |   |
              |       |   + gassign
              |       |   |    code GIMPLE_ASSIGN
              |       |   |
              |       |   + greturn
              |       |        code GIMPLE_RETURN
              |       |
              |       + gcall
              |       |        layout: GSS_CALL, code: GIMPLE_CALL
              |       |
              |       + gasm
              |       |        layout: GSS_ASM, code: GIMPLE_ASM
              |       |
              |       + gtransaction
              |                layout: GSS_TRANSACTION, code: GIMPLE_TRANSACTION
              |
              + gimple_statement_omp
              |   |    layout: GSS_OMP.  Used for code GIMPLE_OMP_SECTION
              |   |
              |   + gomp_critical
              |   |        layout: GSS_OMP_CRITICAL, code: GIMPLE_OMP_CRITICAL
              |   |
              |   + gomp_for
              |   |        layout: GSS_OMP_FOR, code: GIMPLE_OMP_FOR
              |   |
              |   + gomp_parallel_layout
              |   |   |    layout: GSS_OMP_PARALLEL_LAYOUT
              |   |   |
              |   |   + gimple_statement_omp_taskreg
              |   |   |   |
              |   |   |   + gomp_parallel
              |   |   |   |        code: GIMPLE_OMP_PARALLEL
              |   |   |   |
              |   |   |   + gomp_task
              |   |   |            code: GIMPLE_OMP_TASK
              |   |   |
              |   |   + gimple_statement_omp_target
              |   |            code: GIMPLE_OMP_TARGET
              |   |
              |   + gomp_sections
              |   |        layout: GSS_OMP_SECTIONS, code: GIMPLE_OMP_SECTIONS
              |   |
              |   + gimple_statement_omp_single_layout
              |       |    layout: GSS_OMP_SINGLE_LAYOUT
              |       |
              |       + gomp_single
              |       |        code: GIMPLE_OMP_SINGLE
              |       |
              |       + gomp_teams
              |                code: GIMPLE_OMP_TEAMS
              |
              + gbind
              |        layout: GSS_BIND, code: GIMPLE_BIND
              |
              + gcatch
              |        layout: GSS_CATCH, code: GIMPLE_CATCH
              |
              + geh_filter
              |        layout: GSS_EH_FILTER, code: GIMPLE_EH_FILTER
              |
              + geh_else
              |        layout: GSS_EH_ELSE, code: GIMPLE_EH_ELSE
              |
              + geh_mnt
              |        layout: GSS_EH_MNT, code: GIMPLE_EH_MUST_NOT_THROW
              |
              + gphi
              |        layout: GSS_PHI, code: GIMPLE_PHI
              |
              + gimple_statement_eh_ctrl
              |   |    layout: GSS_EH_CTRL
              |   |
              |   + gresx
              |   |        code: GIMPLE_RESX
              |   |
              |   + geh_dispatch
              |            code: GIMPLE_EH_DISPATCH
              |
              + gtry
              |        layout: GSS_TRY, code: GIMPLE_TRY
              |
              + gimple_statement_wce
              |        layout: GSS_WCE, code: GIMPLE_WITH_CLEANUP_EXPR
              |
              + gomp_continue
              |        layout: GSS_OMP_CONTINUE, code: GIMPLE_OMP_CONTINUE
              |
              + gomp_atomic_load
              |        layout: GSS_OMP_ATOMIC_LOAD, code: GIMPLE_OMP_ATOMIC_LOAD
              |
              + gimple_statement_omp_atomic_store_layout
                  |    layout: GSS_OMP_ATOMIC_STORE_LAYOUT,
                  |    code: GIMPLE_OMP_ATOMIC_STORE
                  |
                  + gomp_atomic_store
                  |        code: GIMPLE_OMP_ATOMIC_STORE
                  |
                  + gomp_return
                           code: GIMPLE_OMP_RETURN