From 25f11dfe76f537afd72380a698eba3a98a9f694a Mon Sep 17 00:00:00 2001 From: Eric Botcazou Date: Wed, 15 Apr 2020 21:11:17 +0200 Subject: [PATCH] [Ada] Do not generate useless length check for array initialization 2020-06-17 Eric Botcazou gcc/ada/ * checks.ads (Apply_Length_Check_On_Assignment): Declare. * checks.adb (Apply_Length_Check_On_Assignment): New procedure to apply a length check to an expression in an assignment. * exp_ch5.adb (Expand_Assign_Array): Call it instead of calling Apply_Length_Check to generate a length check. * sem_ch5.adb (Analyze_Assignment): Likewise. --- gcc/ada/checks.adb | 28 ++++++++++++++++++++++++++++ gcc/ada/checks.ads | 9 +++++++++ gcc/ada/exp_ch5.adb | 2 +- gcc/ada/sem_ch5.adb | 4 ++-- 4 files changed, 40 insertions(+), 3 deletions(-) diff --git a/gcc/ada/checks.adb b/gcc/ada/checks.adb index aab9e33..4382951 100644 --- a/gcc/ada/checks.adb +++ b/gcc/ada/checks.adb @@ -2220,6 +2220,34 @@ package body Checks is (Expr, Target_Typ, Source_Typ, Do_Static => False); end Apply_Length_Check; + -------------------------------------- + -- Apply_Length_Check_On_Assignment -- + -------------------------------------- + + procedure Apply_Length_Check_On_Assignment + (Expr : Node_Id; + Target_Typ : Entity_Id; + Target : Node_Id; + Source_Typ : Entity_Id := Empty) + is + Assign : constant Node_Id := Parent (Target); + + begin + -- No check is needed for the initialization of an object whose + -- nominal subtype is unconstrained. + + if Is_Constr_Subt_For_U_Nominal (Target_Typ) + and then Nkind (Parent (Assign)) = N_Freeze_Entity + and then Is_Entity_Name (Target) + and then Entity (Target) = Entity (Parent (Assign)) + then + return; + end if; + + Apply_Selected_Length_Checks + (Expr, Target_Typ, Source_Typ, Do_Static => False); + end Apply_Length_Check_On_Assignment; + ------------------------------------- -- Apply_Parameter_Aliasing_Checks -- ------------------------------------- diff --git a/gcc/ada/checks.ads b/gcc/ada/checks.ads index 6412686..79657c3 100644 --- a/gcc/ada/checks.ads +++ b/gcc/ada/checks.ads @@ -569,6 +569,15 @@ package Checks is -- processes it as described above for consistency with the other routines -- in this section. + procedure Apply_Length_Check_On_Assignment + (Expr : Node_Id; + Target_Typ : Entity_Id; + Target : Node_Id; + Source_Typ : Entity_Id := Empty); + -- Similar to Apply_Length_Check, but takes the target of an assignment for + -- which the check is to be done. Used to filter out specific cases where + -- the check is superfluous. + procedure Apply_Range_Check (Expr : Node_Id; Target_Typ : Entity_Id; diff --git a/gcc/ada/exp_ch5.adb b/gcc/ada/exp_ch5.adb index 0634ffc..fd51dfa 100644 --- a/gcc/ada/exp_ch5.adb +++ b/gcc/ada/exp_ch5.adb @@ -441,7 +441,7 @@ package body Exp_Ch5 is -- respect to the right-hand side as given, not a possible underlying -- renamed object, since this would generate incorrect extra checks. - Apply_Length_Check (Rhs, L_Type); + Apply_Length_Check_On_Assignment (Rhs, L_Type, Lhs); -- We start by assuming that the move can be done in either direction, -- i.e. that the two sides are completely disjoint. diff --git a/gcc/ada/sem_ch5.adb b/gcc/ada/sem_ch5.adb index 01f0b50..36633cb 100644 --- a/gcc/ada/sem_ch5.adb +++ b/gcc/ada/sem_ch5.adb @@ -995,7 +995,7 @@ package body Sem_Ch5 is and then (Nkind (Rhs) /= N_Function_Call or else Nkind (N) /= N_Block_Statement) then - -- Assignment verifies that the length of the Lsh and Rhs are equal, + -- Assignment verifies that the length of the Lhs and Rhs are equal, -- but of course the indexes do not have to match. If the right-hand -- side is a type conversion to an unconstrained type, a length check -- is performed on the expression itself during expansion. In rare @@ -1003,7 +1003,7 @@ package body Sem_Ch5 is -- with a different representation, triggering incorrect code in the -- back end. - Apply_Length_Check (Rhs, Etype (Lhs)); + Apply_Length_Check_On_Assignment (Rhs, Etype (Lhs), Lhs); else -- Discriminant checks are applied in the course of expansion -- 2.7.4