diff options
Diffstat (limited to 'gcc/gimple-low.c')
| -rw-r--r-- | gcc/gimple-low.c | 75 |
1 files changed, 58 insertions, 17 deletions
diff --git a/gcc/gimple-low.c b/gcc/gimple-low.c index b58fd7b42f5..cce31e946ff 100644 --- a/gcc/gimple-low.c +++ b/gcc/gimple-low.c @@ -76,6 +76,9 @@ struct lower_data of the function. */ VEC(return_statements_t,heap) *return_statements; + /* True if the current statement cannot fall through. */ + bool cannot_fallthru; + /* True if the function calls __builtin_setjmp. */ bool calls_builtin_setjmp; }; @@ -317,7 +320,12 @@ lower_omp_directive (gimple_stmt_iterator *gsi, struct lower_data *data) } -/* Lower statement GSI. DATA is passed through the recursion. */ +/* Lower statement GSI. DATA is passed through the recursion. We try to + track the fallthruness of statements and get rid of unreachable return + statements in order to prevent the EH lowering pass from adding useless + edges that can cause bogus warnings to be issued later; this guess need + not be 100% accurate, simply be conservative and reset cannot_fallthru + to false if we don't know. */ static void lower_stmt (gimple_stmt_iterator *gsi, struct lower_data *data) @@ -330,36 +338,61 @@ lower_stmt (gimple_stmt_iterator *gsi, struct lower_data *data) { case GIMPLE_BIND: lower_gimple_bind (gsi, data); + /* Propagate fallthruness. */ return; case GIMPLE_COND: - /* The gimplifier has already lowered this into gotos. */ - break; + case GIMPLE_GOTO: + case GIMPLE_SWITCH: + data->cannot_fallthru = true; + gsi_next (gsi); + return; case GIMPLE_RETURN: - lower_gimple_return (gsi, data); + if (data->cannot_fallthru) + { + gsi_remove (gsi, false); + /* Propagate fallthruness. */ + } + else + { + lower_gimple_return (gsi, data); + data->cannot_fallthru = true; + } return; case GIMPLE_TRY: - lower_sequence (gimple_try_eval (stmt), data); - lower_sequence (gimple_try_cleanup (stmt), data); + { + bool try_cannot_fallthru; + lower_sequence (gimple_try_eval (stmt), data); + try_cannot_fallthru = data->cannot_fallthru; + data->cannot_fallthru = false; + lower_sequence (gimple_try_cleanup (stmt), data); + /* See gimple_stmt_may_fallthru for the rationale. */ + if (gimple_try_kind (stmt) == GIMPLE_TRY_FINALLY) + { + data->cannot_fallthru |= try_cannot_fallthru; + gsi_next (gsi); + return; + } + } break; case GIMPLE_CATCH: + data->cannot_fallthru = false; lower_sequence (gimple_catch_handler (stmt), data); break; case GIMPLE_EH_FILTER: + data->cannot_fallthru = false; lower_sequence (gimple_eh_filter_failure (stmt), data); break; case GIMPLE_NOP: case GIMPLE_ASM: case GIMPLE_ASSIGN: - case GIMPLE_GOTO: case GIMPLE_PREDICT: case GIMPLE_LABEL: - case GIMPLE_SWITCH: case GIMPLE_EH_MUST_NOT_THROW: case GIMPLE_OMP_FOR: case GIMPLE_OMP_SECTIONS: @@ -383,8 +416,16 @@ lower_stmt (gimple_stmt_iterator *gsi, struct lower_data *data) && DECL_BUILT_IN_CLASS (decl) == BUILT_IN_NORMAL && DECL_FUNCTION_CODE (decl) == BUILT_IN_SETJMP) { - data->calls_builtin_setjmp = true; lower_builtin_setjmp (gsi); + data->cannot_fallthru = false; + data->calls_builtin_setjmp = true; + return; + } + + if (decl && (flags_from_decl_or_type (decl) & ECF_NORETURN)) + { + data->cannot_fallthru = true; + gsi_next (gsi); return; } } @@ -392,13 +433,16 @@ lower_stmt (gimple_stmt_iterator *gsi, struct lower_data *data) case GIMPLE_OMP_PARALLEL: case GIMPLE_OMP_TASK: + data->cannot_fallthru = false; lower_omp_directive (gsi, data); + data->cannot_fallthru = false; return; default: gcc_unreachable (); } + data->cannot_fallthru = false; gsi_next (gsi); } @@ -647,9 +691,9 @@ gimple_stmt_may_fallthru (gimple stmt) return false; case GIMPLE_SWITCH: - /* Switch has already been lowered and represents a - branch to a selected label and hence can not fall through. */ - return true; + /* Switch has already been lowered and represents a branch + to a selected label and hence can't fall through. */ + return false; case GIMPLE_COND: /* GIMPLE_COND's are already lowered into a two-way branch. They @@ -675,13 +719,10 @@ gimple_stmt_may_fallthru (gimple stmt) return (gimple_seq_may_fallthru (gimple_try_eval (stmt)) && gimple_seq_may_fallthru (gimple_try_cleanup (stmt))); - case GIMPLE_ASSIGN: - return true; - case GIMPLE_CALL: /* Functions that do not return do not fall through. */ return (gimple_call_flags (stmt) & ECF_NORETURN) == 0; - + default: return true; } @@ -731,7 +772,7 @@ lower_gimple_return (gimple_stmt_iterator *gsi, struct lower_data *data) gsi_remove (gsi, false); } -/* Lower a __builtin_setjmp TSI. +/* Lower a __builtin_setjmp GSI. __builtin_setjmp is passed a pointer to an array of five words (not all will be used on all machines). It operates similarly to the C |