From: Johannes Kliemann <kliem...@adacore.com>
On targets with preallocated task stacks the minimum stack size is
defined as a constant in System.Parameters. When adding preallocated
tasks to the expanded code the compiler does not have direct access to
that value. Instead generate the expression
Max (Task_Size, Minimum_Task_Size) in the expanded tree and let it be
resolved later in the compilation process.
gcc/ada/ChangeLog:
* exp_ch9.adb (Expand_N_Task_Type_Declaration): Take
Minimum_Stack_Size into account when preallocating task stacks.
* rtsfind.ads (RE_Id, RE_Unit_Table): Add RE_Minimum_Stack_Size.
Tested on x86_64-pc-linux-gnu, committed on master.
---
gcc/ada/exp_ch9.adb | 29 +++++++++++++++++++++++++++++
gcc/ada/rtsfind.ads | 2 ++
2 files changed, 31 insertions(+)
diff --git a/gcc/ada/exp_ch9.adb b/gcc/ada/exp_ch9.adb
index cf4d4d82256..df51856f9c9 100644
--- a/gcc/ada/exp_ch9.adb
+++ b/gcc/ada/exp_ch9.adb
@@ -11945,6 +11945,35 @@ package body Exp_Ch9 is
else
Task_Size := New_Copy_Tree (Expr_N);
end if;
+
+ -- On targets with a preallocated task stack the minimum stack
+ -- size is defined in System.Parameters. Since we do not have
+ -- access to the value of that definition here we replace the
+ -- static task size with the static expression
+ -- Size_Type'Max (Task_Size, Minimum_Stack_Size).
+ -- The compiler will evaluate this expression and replace the
+ -- task size with the Minimum_Stack_Size if needed. It is
+ -- important for this expression to be static to avoid
+ -- introducing implicit heap allocations that would break code
+ -- with the No_Implicit_Heap_Allocations restriction.
+ -- On some runtimes the allocation of the minimum stack size is
+ -- ensured by a call to Adjust_Storage_Size. We cannot use this
+ -- function here as it is not static and evaluated at runtime.
+ -- Note: This expression may not appear in the expanded code
+ -- as the compiler evaluates this expression before code
+ -- generation.
+
+ Task_Size :=
+ Convert_To
+ (RTE (RE_Storage_Offset),
+ Make_Attribute_Reference (Loc,
+ Attribute_Name => Name_Max,
+ Prefix =>
+ New_Occurrence_Of
+ (RTE (RE_Size_Type), Loc), Expressions => New_List (
+ Convert_To (RTE (RE_Size_Type), Task_Size),
+ New_Occurrence_Of (RTE (RE_Minimum_Stack_Size),
+ Loc))));
end;
else
diff --git a/gcc/ada/rtsfind.ads b/gcc/ada/rtsfind.ads
index 9cfd2ed4c48..16c817dc37e 100644
--- a/gcc/ada/rtsfind.ads
+++ b/gcc/ada/rtsfind.ads
@@ -1618,6 +1618,7 @@ package Rtsfind is
RE_Adjust_Storage_Size, -- System.Parameters
RE_Default_Stack_Size, -- System.Parameters
+ RE_Minimum_Stack_Size, -- System.Parameters
RE_Size_Type, -- System.Parameters
RE_Unspecified_Size, -- System.Parameters
@@ -3274,6 +3275,7 @@ package Rtsfind is
RE_Adjust_Storage_Size => System_Parameters,
RE_Default_Stack_Size => System_Parameters,
+ RE_Minimum_Stack_Size => System_Parameters,
RE_Size_Type => System_Parameters,
RE_Unspecified_Size => System_Parameters,
--
2.43.0
