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Implement support for case statements in Ada #171

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Merged
merged 5 commits into from
Mar 27, 2019
Merged

Implement support for case statements in Ada #171

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7cb8f2f
Implement support for case statements in Ada.
NlightNFotis Mar 22, 2019
8bcddce
Add a small fix to support others, and add tests.
NlightNFotis Mar 25, 2019
848a008
Handle multiple values in case statement and add tests
NlightNFotis Mar 26, 2019
1e639b3
Add failing test for case statement and ranges
NlightNFotis Mar 26, 2019
4e64f08
Implement comment suggestions and change tests to return ints
NlightNFotis Mar 27, 2019
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57 changes: 56 additions & 1 deletion gnat2goto/driver/tree_walk.adb
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,10 @@ package body Tree_Walk is
with Pre => Nkind (N) = N_Loop_Statement,
Post => Kind (Do_Loop_Statement'Result) in Class_Code;

function Do_Case_Statement (N : Node_Id) return Irep
with Pre => Nkind (N) = N_Case_Statement,
Post => Kind (Do_Case_Statement'Result) = I_Code_Block;

function Do_N_Block_Statement (N : Node_Id) return Irep
with Pre => Nkind (N) = N_Block_Statement,
Post => Kind (Do_N_Block_Statement'Result) = I_Code_Block;
Expand Down Expand Up @@ -1764,6 +1768,57 @@ package body Tree_Walk is
Do_Type_Declaration (New_Type, Typedef);
end Do_Itype_Reference;

-----------------------
-- Do_Case_Statement --
-----------------------

function Do_Case_Statement (N : Node_Id) return Irep is
Ret : constant Irep := New_Irep (I_Code_Block);
Value : constant Irep := Do_Expression (Expression (N));

-- Auxiliary function to create a single test case
-- to emplace in a condition from a list of alternative
-- values.
function Make_Single_Test (Alt : Node_Id) return Irep;
function Make_Single_Test (Alt : Node_Id) return Irep is
Ret : constant Irep := New_Irep (I_Op_Eq);
Rhs : constant Irep := Do_Expression (Alt);
begin
Set_Lhs (Ret, Value);
Set_Rhs (Ret, Rhs);
Set_Type (Ret, New_Irep (I_Bool_Type));
return Ret;
end Make_Single_Test;

This_Alt : Node_Id := First (Alternatives (N));
begin
-- Do-while loop because there must be at least one alternative.
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Maybe I am just old and paranoid BUT ... if you are assuming something it is best to make it an assert rather than a comment; even if it is 'obvious'.

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Definitely worth asserting, but the grammar does indeed guarantee this is true for now (but again, worth checking anyway, who knows what's going to happen in Ada 2023)
https://www.adaic.org/resources/add_content/standards/05rm/html/RM-3-8-1.html#S0073

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Parent link of one Hannes posted (case statements)
https://www.adaic.org/resources/add_content/standards/05rm/html/RM-5-4.html

loop
declare
This_Stmt : constant Irep :=
Process_Statements (Statements (This_Alt));
This_Alt_Copy : constant Node_Id := This_Alt;
This_Test : Irep;
begin
Next (This_Alt);
if not Present (This_Alt) then
-- Omit test, this is either `others`
-- or the last case of complete coverage
This_Test := This_Stmt;
else
This_Test := New_Irep (I_Code_Ifthenelse);
Set_Cond (This_Test,
Make_Single_Test
(First (Discrete_Choices (This_Alt_Copy))));
Set_Then_Case (This_Test, This_Stmt);
Append_Op (Ret, This_Test);
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I guess this line (and 1829) could be moved after the if-then-else block.

end if;
end;
exit when not Present (This_Alt);
end loop;
return Ret;
end Do_Case_Statement;

-----------------------
-- Do_Loop_Statement --
-----------------------
Expand Down Expand Up @@ -4031,7 +4086,7 @@ package body Tree_Walk is
Append_Op (Block, Do_If_Statement (N));

when N_Case_Statement =>
Warn_Unhandled_Construct (Statement, "case");
Append_Op (Block, Do_Case_Statement (N));

when N_Loop_Statement =>
Append_Op (Block, Do_Loop_Statement (N));
Expand Down