diff options
Diffstat (limited to 'gcc/ada/sem_ch5.adb')
| -rw-r--r-- | gcc/ada/sem_ch5.adb | 63 |
1 files changed, 54 insertions, 9 deletions
diff --git a/gcc/ada/sem_ch5.adb b/gcc/ada/sem_ch5.adb index 6b799ee5979..0077db2677a 100644 --- a/gcc/ada/sem_ch5.adb +++ b/gcc/ada/sem_ch5.adb @@ -597,6 +597,12 @@ package body Sem_Ch5 is ---------------------------- procedure Analyze_Case_Statement (N : Node_Id) is + Exp : Node_Id; + Exp_Type : Entity_Id; + Exp_Btype : Entity_Id; + Last_Choice : Nat; + Dont_Care : Boolean; + Others_Present : Boolean; Statements_Analyzed : Boolean := False; -- Set True if at least some statement sequences get analyzed. @@ -640,22 +646,61 @@ package body Sem_Ch5 is ------------------------ procedure Process_Statements (Alternative : Node_Id) is + Choices : constant List_Id := Discrete_Choices (Alternative); + Ent : Entity_Id; + begin Unblocked_Exit_Count := Unblocked_Exit_Count + 1; Statements_Analyzed := True; + + -- An interesting optimization. If the case statement expression + -- is a simple entity, then we can set the current value within + -- an alternative if the alternative has one possible value. + + -- case N is + -- when 1 => alpha + -- when 2 | 3 => beta + -- when others => gamma + + -- Here we know that N is initially 1 within alpha, but for beta + -- and gamma, we do not know anything more about the initial value. + + if Is_Entity_Name (Exp) then + Ent := Entity (Exp); + + if Ekind (Ent) = E_Variable + or else + Ekind (Ent) = E_In_Out_Parameter + or else + Ekind (Ent) = E_Out_Parameter + then + if List_Length (Choices) = 1 + and then Nkind (First (Choices)) in N_Subexpr + and then Compile_Time_Known_Value (First (Choices)) + then + Set_Current_Value (Entity (Exp), First (Choices)); + end if; + + Analyze_Statements (Statements (Alternative)); + + -- After analyzing the case, set the current value to empty + -- since we won't know what it is for the next alternative + -- (unless reset by this same circuit), or after the case. + + Set_Current_Value (Entity (Exp), Empty); + return; + end if; + end if; + + -- Case where expression is not an entity name of a variable + Analyze_Statements (Statements (Alternative)); end Process_Statements; - -- Variables local to Analyze_Case_Statement. - - Exp : Node_Id; - Exp_Type : Entity_Id; - Exp_Btype : Entity_Id; + -- Table to record choices. Put after subprograms since we make + -- a call to Number_Of_Choices to get the right number of entries. - Case_Table : Choice_Table_Type (1 .. Number_Of_Choices (N)); - Last_Choice : Nat; - Dont_Care : Boolean; - Others_Present : Boolean; + Case_Table : Choice_Table_Type (1 .. Number_Of_Choices (N)); -- Start of processing for Analyze_Case_Statement |