[gcc(refs/users/aoliva/heads/testme)] add alignment to enable store merging in strict-alignment targets

[gcc(refs/users/aoliva/heads/testme)] add alignment to enable store merging in strict-alignment targets

[Alexandre Oliva]

https://gcc.gnu.org/g:c247f78275448e8da74284ed1be77b05941425df

commit c247f78275448e8da74284ed1be77b05941425df
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Thu Dec 31 21:38:35 2020 -0300

    add alignment to enable store merging in strict-alignment targets
    
    In g++.dg/opt/store-merging-2.C, the natural alignment of types T and
    S is a single byte, so we shouldn't expect store merging on
    strict-alignment platforms.  Indeed, without something like the
    adjust-alignment pass to bump up the alignment of the automatic
    variable, as in GCC 10, the optimization does not occur.
    
    This patch adjusts the test so that the required alignment is
    expressly stated, and so we don't rely on its accidentally being there
    to get the desired optimization.
    
    
    for  gcc/testsuite/ChangeLog
    
            * g++.dg/opt/store-merging-2.C: Add the required alignment.

Diff:
---
 gcc/testsuite/g++.dg/opt/store-merging-2.C | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/g++.dg/opt/store-merging-2.C b/gcc/testsuite/g++.dg/opt/store-merging-2.C
index 3c17033764b..b1ad7018a17 100644
--- a/gcc/testsuite/g++.dg/opt/store-merging-2.C
+++ b/gcc/testsuite/g++.dg/opt/store-merging-2.C
@@ -4,7 +4,9 @@
 // { dg-options "-O2 -flifetime-dse=2 -fdump-tree-store-merging-details" }
 // { dg-final { scan-tree-dump "New sequence of 2 stores to replace old one of 3 stores" "store-merging" } }
 
-struct T { char a[128]; };
+/* The alignment is necessary for store-merging to take place on
+   strict-alignment targets.  */
+struct __attribute__ ((__aligned__ (4))) T { char a[128]; };
 struct S { S () : a () { a.a[12] = 0; a.a[13] = 1; a.a[14] = 0; a.a[15] = 6; } T a; };
 void foo (S &);
 void bar (void) { S s; foo (s); }

[gcc(refs/users/aoliva/heads/testme)] add alignment to enable store merging in strict-alignment targets

[Alexandre Oliva]

https://gcc.gnu.org/g:85649d9570298561bf4d8bd086593f8958fc1b4e

commit 85649d9570298561bf4d8bd086593f8958fc1b4e
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Thu Dec 31 21:38:35 2020 -0300

    add alignment to enable store merging in strict-alignment targets
    
    In g++.dg/opt/store-merging-2.C, the natural alignment of types T and
    S is a single byte, so we shouldn't expect store merging on
    strict-alignment platforms.  Indeed, without something like the
    adjust-alignment pass to bump up the alignment of the automatic
    variable, as in GCC 10, the optimization does not occur.
    
    This patch adjusts the test so that the required alignment is
    expressly stated, and so we don't rely on its accidentally being there
    to get the desired optimization.
    
    
    for  gcc/testsuite/ChangeLog
    
            * g++.dg/opt/store-merging-2.C: Add the required alignment.

Diff:
---
 gcc/testsuite/g++.dg/opt/store-merging-2.C | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/g++.dg/opt/store-merging-2.C b/gcc/testsuite/g++.dg/opt/store-merging-2.C
index 3c17033764b..b1ad7018a17 100644
--- a/gcc/testsuite/g++.dg/opt/store-merging-2.C
+++ b/gcc/testsuite/g++.dg/opt/store-merging-2.C
@@ -4,7 +4,9 @@
 // { dg-options "-O2 -flifetime-dse=2 -fdump-tree-store-merging-details" }
 // { dg-final { scan-tree-dump "New sequence of 2 stores to replace old one of 3 stores" "store-merging" } }
 
-struct T { char a[128]; };
+/* The alignment is necessary for store-merging to take place on
+   strict-alignment targets.  */
+struct __attribute__ ((__aligned__ (4))) T { char a[128]; };
 struct S { S () : a () { a.a[12] = 0; a.a[13] = 1; a.a[14] = 0; a.a[15] = 6; } T a; };
 void foo (S &);
 void bar (void) { S s; foo (s); }