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* [gcc r13-241] [Ada] Cleanup unnecessary declare block in Check_Unreachable_Code
@ 2022-05-10 8:22 Pierre-Marie de Rodat
0 siblings, 0 replies; only message in thread
From: Pierre-Marie de Rodat @ 2022-05-10 8:22 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:ea22ec90df9649465b172269027fff8f0750047b
commit r13-241-gea22ec90df9649465b172269027fff8f0750047b
Author: Piotr Trojanek <trojanek@adacore.com>
Date: Thu Jan 20 22:36:16 2022 +0100
[Ada] Cleanup unnecessary declare block in Check_Unreachable_Code
Cleanup related to static detection of references to uninitialized
variables. Semantics is unaffected.
gcc/ada/
* sem_ch5.adb (Check_Unreachable_Code): Remove inner declare
block; refill code and comments.
Diff:
---
gcc/ada/sem_ch5.adb | 200 +++++++++++++++++++++++++---------------------------
1 file changed, 98 insertions(+), 102 deletions(-)
diff --git a/gcc/ada/sem_ch5.adb b/gcc/ada/sem_ch5.adb
index 41b9ae02276..81767d8c324 100644
--- a/gcc/ada/sem_ch5.adb
+++ b/gcc/ada/sem_ch5.adb
@@ -4397,149 +4397,145 @@ package body Sem_Ch5 is
procedure Check_Unreachable_Code (N : Node_Id) is
Error_Node : Node_Id;
+ Nxt : Node_Id;
P : Node_Id;
begin
if Is_List_Member (N) and then Comes_From_Source (N) then
- declare
- Nxt : Node_Id;
+ Nxt := Original_Node (Next (N));
- begin
- Nxt := Original_Node (Next (N));
+ -- Skip past pragmas
- -- Skip past pragmas
+ while Nkind (Nxt) = N_Pragma loop
+ Nxt := Original_Node (Next (Nxt));
+ end loop;
- while Nkind (Nxt) = N_Pragma loop
- Nxt := Original_Node (Next (Nxt));
- end loop;
+ -- If a label follows us, then we never have dead code, since someone
+ -- could branch to the label, so we just ignore it.
- -- If a label follows us, then we never have dead code, since
- -- someone could branch to the label, so we just ignore it.
+ if Nkind (Nxt) = N_Label then
+ return;
- if Nkind (Nxt) = N_Label then
- return;
+ -- Otherwise see if we have a real statement following us
- -- Otherwise see if we have a real statement following us
+ elsif Present (Nxt)
+ and then Comes_From_Source (Nxt)
+ and then Is_Statement (Nxt)
+ then
+ -- Special very annoying exception. If we have a return that
+ -- follows a raise, then we allow it without a warning, since
+ -- the Ada RM annoyingly requires a useless return here.
- elsif Present (Nxt)
- and then Comes_From_Source (Nxt)
- and then Is_Statement (Nxt)
+ if Nkind (Original_Node (N)) /= N_Raise_Statement
+ or else Nkind (Nxt) /= N_Simple_Return_Statement
then
- -- Special very annoying exception. If we have a return that
- -- follows a raise, then we allow it without a warning, since
- -- the Ada RM annoyingly requires a useless return here.
-
- if Nkind (Original_Node (N)) /= N_Raise_Statement
- or else Nkind (Nxt) /= N_Simple_Return_Statement
- then
- -- The rather strange shenanigans with the warning message
- -- here reflects the fact that Kill_Dead_Code is very good
- -- at removing warnings in deleted code, and this is one
- -- warning we would prefer NOT to have removed.
-
- Error_Node := Nxt;
+ -- The rather strange shenanigans with the warning message
+ -- here reflects the fact that Kill_Dead_Code is very good at
+ -- removing warnings in deleted code, and this is one warning
+ -- we would prefer NOT to have removed.
- -- If we have unreachable code, analyze and remove the
- -- unreachable code, since it is useless and we don't
- -- want to generate junk warnings.
+ Error_Node := Nxt;
- -- We skip this step if we are not in code generation mode
- -- or CodePeer mode.
+ -- If we have unreachable code, analyze and remove the
+ -- unreachable code, since it is useless and we don't want
+ -- to generate junk warnings.
- -- This is the one case where we remove dead code in the
- -- semantics as opposed to the expander, and we do not want
- -- to remove code if we are not in code generation mode,
- -- since this messes up the tree or loses useful information
- -- for CodePeer.
+ -- We skip this step if we are not in code generation mode
+ -- or CodePeer mode.
- -- Note that one might react by moving the whole circuit to
- -- exp_ch5, but then we lose the warning in -gnatc mode.
+ -- This is the one case where we remove dead code in the
+ -- semantics as opposed to the expander, and we do not want
+ -- to remove code if we are not in code generation mode, since
+ -- this messes up the tree or loses useful information for
+ -- CodePeer.
- if Operating_Mode = Generate_Code
- and then not CodePeer_Mode
- then
- loop
- Nxt := Next (N);
+ -- Note that one might react by moving the whole circuit to
+ -- exp_ch5, but then we lose the warning in -gnatc mode.
- -- Quit deleting when we have nothing more to delete
- -- or if we hit a label (since someone could transfer
- -- control to a label, so we should not delete it).
+ if Operating_Mode = Generate_Code
+ and then not CodePeer_Mode
+ then
+ loop
+ Nxt := Next (N);
- exit when No (Nxt) or else Nkind (Nxt) = N_Label;
+ -- Quit deleting when we have nothing more to delete
+ -- or if we hit a label (since someone could transfer
+ -- control to a label, so we should not delete it).
- -- Statement/declaration is to be deleted
+ exit when No (Nxt) or else Nkind (Nxt) = N_Label;
- Analyze (Nxt);
- Remove (Nxt);
- Kill_Dead_Code (Nxt);
- end loop;
- end if;
+ -- Statement/declaration is to be deleted
- Error_Msg
- ("??unreachable code!", Sloc (Error_Node), Error_Node);
+ Analyze (Nxt);
+ Remove (Nxt);
+ Kill_Dead_Code (Nxt);
+ end loop;
end if;
- -- If the unconditional transfer of control instruction is the
- -- last statement of a sequence, then see if our parent is one of
- -- the constructs for which we count unblocked exits, and if so,
- -- adjust the count.
-
- else
- P := Parent (N);
+ Error_Msg
+ ("??unreachable code!", Sloc (Error_Node), Error_Node);
+ end if;
- -- Statements in THEN part or ELSE part of IF statement
+ -- If the unconditional transfer of control instruction is the
+ -- last statement of a sequence, then see if our parent is one of
+ -- the constructs for which we count unblocked exits, and if so,
+ -- adjust the count.
- if Nkind (P) = N_If_Statement then
- null;
+ else
+ P := Parent (N);
- -- Statements in ELSIF part of an IF statement
+ -- Statements in THEN part or ELSE part of IF statement
- elsif Nkind (P) = N_Elsif_Part then
- P := Parent (P);
- pragma Assert (Nkind (P) = N_If_Statement);
+ if Nkind (P) = N_If_Statement then
+ null;
- -- Statements in CASE statement alternative
+ -- Statements in ELSIF part of an IF statement
- elsif Nkind (P) = N_Case_Statement_Alternative then
- P := Parent (P);
- pragma Assert (Nkind (P) = N_Case_Statement);
+ elsif Nkind (P) = N_Elsif_Part then
+ P := Parent (P);
+ pragma Assert (Nkind (P) = N_If_Statement);
- -- Statements in body of block
+ -- Statements in CASE statement alternative
- elsif Nkind (P) = N_Handled_Sequence_Of_Statements
- and then Nkind (Parent (P)) = N_Block_Statement
- then
- -- The original loop is now placed inside a block statement
- -- due to the expansion of attribute 'Loop_Entry. Return as
- -- this is not a "real" block for the purposes of exit
- -- counting.
+ elsif Nkind (P) = N_Case_Statement_Alternative then
+ P := Parent (P);
+ pragma Assert (Nkind (P) = N_Case_Statement);
- if Nkind (N) = N_Loop_Statement
- and then Subject_To_Loop_Entry_Attributes (N)
- then
- return;
- end if;
+ -- Statements in body of block
- -- Statements in exception handler in a block
+ elsif Nkind (P) = N_Handled_Sequence_Of_Statements
+ and then Nkind (Parent (P)) = N_Block_Statement
+ then
+ -- The original loop is now placed inside a block statement
+ -- due to the expansion of attribute 'Loop_Entry. Return as
+ -- this is not a "real" block for the purposes of exit
+ -- counting.
- elsif Nkind (P) = N_Exception_Handler
- and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
- and then Nkind (Parent (Parent (P))) = N_Block_Statement
+ if Nkind (N) = N_Loop_Statement
+ and then Subject_To_Loop_Entry_Attributes (N)
then
- null;
-
- -- None of these cases, so return
-
- else
return;
end if;
- -- This was one of the cases we are looking for (i.e. the
- -- parent construct was IF, CASE or block) so decrement count.
+ -- Statements in exception handler in a block
- Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
+ elsif Nkind (P) = N_Exception_Handler
+ and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
+ and then Nkind (Parent (Parent (P))) = N_Block_Statement
+ then
+ null;
+
+ -- None of these cases, so return
+
+ else
+ return;
end if;
- end;
+
+ -- This was one of the cases we are looking for (i.e. the parent
+ -- construct was IF, CASE or block) so decrement count.
+
+ Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
+ end if;
end if;
end Check_Unreachable_Code;
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