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| -rw-r--r-- | gcc/recog.h | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/gcc/recog.h b/gcc/recog.h index d6af2aa66d9..b8de43b95bb 100644 --- a/gcc/recog.h +++ b/gcc/recog.h @@ -503,6 +503,57 @@ alternative_mask get_preferred_alternatives (rtx_insn *, basic_block); bool check_bool_attrs (rtx_insn *); void recog_init (); + +/* This RAII class can help to undo tentative insn changes on failure. + When an object of the class goes out of scope, it undoes all group + changes that have been made via the validate_change machinery and + not yet confirmed via confirm_change_group. + + For example: + + insn_change_watermark watermark; + validate_change (..., true); // A + ... + if (test) + // Undoes change A. + return false; + ... + validate_change (..., true); // B + ... + if (test) + // Undoes changes A and B. + return false; + ... + confirm_change_group (); + + Code that wants to avoid this behavior can use keep (): + + insn_change_watermark watermark; + validate_change (..., true); // A + ... + if (test) + // Undoes change A. + return false; + ... + watermark.keep (); + validate_change (..., true); // B + ... + if (test) + // Undoes change B, but not A. + return false; + ... + confirm_change_group (); */ +class insn_change_watermark +{ +public: + insn_change_watermark () : m_old_num_changes (num_validated_changes ()) {} + ~insn_change_watermark () { cancel_changes (m_old_num_changes); } + void keep () { m_old_num_changes = num_validated_changes (); } + +private: + int m_old_num_changes; +}; + #endif #endif /* GCC_RECOG_H */ |