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| author | Eric Botcazou <ebotcazou@adacore.com> | 2019-09-19 08:14:47 +0000 |
|---|---|---|
| committer | Pierre-Marie de Rodat <pmderodat@gcc.gnu.org> | 2019-09-19 08:14:47 +0000 |
| commit | c3a75a09b8424c192b32a39fa273d27db5b9c039 (patch) | |
| tree | 02248dbe080cb8039d06d8da007945feaac10b45 /gcc/ada | |
| parent | 87cd385fa5dad3a0e5d144e08670c7fdd85fe2ef (diff) | |
| download | gcc-c3a75a09b8424c192b32a39fa273d27db5b9c039.zip gcc-c3a75a09b8424c192b32a39fa273d27db5b9c039.tar.gz gcc-c3a75a09b8424c192b32a39fa273d27db5b9c039.tar.bz2 | |
[Ada] Get rid of useless temporary for slice in overaligned record type
This fixes a recent code quality regression for targets that do not
require the strict alignment of memory accesses: the compiler would
generate a useless temporary for a slice of an array component in an
overaligned record type.
Running these commands:
gcc -c p.adb -gnatws -gnatD
grep loop p.adb.dg
On the following sources:
procedure P (N : Positive) is
type Rec1 is record
I : Integer;
end record;
type Arr is array (Positive range <>) of Rec1;
type Rec2 is record
A : Arr (1 .. 128);
end record;
for Rec2'Alignment use 8;
procedure Proc (A : Arr) is
begin
null;
end;
R : Rec2;
begin
Proc (R.A (1 .. N));
end;
Should execute silently.
2019-09-19 Eric Botcazou <ebotcazou@adacore.com>
gcc/ada/
* exp_util.adb (Is_Possibly_Unaligned_Slice): Do not return true
on pure alignment considerations if the target does not require
the strict alignment of memory accesses.
From-SVN: r275956
Diffstat (limited to 'gcc/ada')
| -rw-r--r-- | gcc/ada/ChangeLog | 6 | ||||
| -rw-r--r-- | gcc/ada/exp_util.adb | 6 |
2 files changed, 10 insertions, 2 deletions
diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog index 8a87274..5808008 100644 --- a/gcc/ada/ChangeLog +++ b/gcc/ada/ChangeLog @@ -1,5 +1,11 @@ 2019-09-19 Eric Botcazou <ebotcazou@adacore.com> + * exp_util.adb (Is_Possibly_Unaligned_Slice): Do not return true + on pure alignment considerations if the target does not require + the strict alignment of memory accesses. + +2019-09-19 Eric Botcazou <ebotcazou@adacore.com> + * sem_ch12.adb (Check_Private_View): Add a comment to indicate future work. diff --git a/gcc/ada/exp_util.adb b/gcc/ada/exp_util.adb index 905e3f4..6306320 100644 --- a/gcc/ada/exp_util.adb +++ b/gcc/ada/exp_util.adb @@ -8692,9 +8692,11 @@ package body Exp_Util is -- We are definitely in trouble if the record in question -- has an alignment, and either we know this alignment is -- inconsistent with the alignment of the slice, or we don't - -- know what the alignment of the slice should be. + -- know what the alignment of the slice should be. But this + -- really matters only if the target has strict alignment. - if Known_Alignment (Ptyp) + if Target_Strict_Alignment + and then Known_Alignment (Ptyp) and then (Unknown_Alignment (Styp) or else Alignment (Styp) > Alignment (Ptyp)) then |