[x86,testsuite] preserve full register across main

Message ID orzhjz4uov.fsf@lxoliva.fsfla.org
State New
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  • [x86,testsuite] preserve full register across main
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Commit Message

Alexandre Oliva Aug. 23, 2019, 6:12 p.m.
This test uses a call-saved register as a global variable.  It
attempts to preserve its value across main, but only the lower int
part is preserved, which is not good enough for x86_64, when the
runtime that calls main() happens to hold something in the chosen
register that is not a zero-extension from the 32-bit value, and
rightfully expects the full register to remain unchanged when main()
returns.

Tested on x86_64-linux-gnu, both -m64 and -m32.  Ok to install?


for  gcc/testsuite/ChangeLog

	* gcc.target/i386/20020616-1.c: Preserve full register across
	main.
---
 gcc/testsuite/gcc.target/i386/20020616-1.c |   14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)


-- 
Alexandre Oliva, freedom fighter  he/him   https://FSFLA.org/blogs/lxo
Be the change, be Free!                 FSF Latin America board member
GNU Toolchain Engineer                        Free Software Evangelist
Hay que enGNUrecerse, pero sin perder la terGNUra jamás - Che GNUevara

Comments

Uros Bizjak Aug. 24, 2019, 8:35 a.m. | #1
On Friday, August 23, 2019, Alexandre Oliva <oliva@adacore.com> wrote:
> This test uses a call-saved register as a global variable.  It

> attempts to preserve its value across main, but only the lower int

> part is preserved, which is not good enough for x86_64, when the

> runtime that calls main() happens to hold something in the chosen

> register that is not a zero-extension from the 32-bit value, and

> rightfully expects the full register to remain unchanged when main()

> returns.

>

> Tested on x86_64-linux-gnu, both -m64 and -m32.  Ok to install?

>

>

> for  gcc/testsuite/ChangeLog

>

>         * gcc.target/i386/20020616-1.c: Preserve full register across

>         main.

> ---

>  gcc/testsuite/gcc.target/i386/20020616-1.c |   14 +++++++++-----

>  1 file changed, 9 insertions(+), 5 deletions(-)

>

> diff --git a/gcc/testsuite/gcc.target/i386/20020616-1.c

b/gcc/testsuite/gcc.target/i386/20020616-1.c
> index 5641826b4837..3b8cf8e41783 100644

> --- a/gcc/testsuite/gcc.target/i386/20020616-1.c

> +++ b/gcc/testsuite/gcc.target/i386/20020616-1.c

> @@ -2,12 +2,16 @@

>  /* { dg-do run } */

>  /* { dg-options "-O2" } */

>

> +/* We need this type to be as wide as the register chosen below, so

> +   that, when we preserve it across main, we preserve all of it.  */

> +typedef long reg_type;


Can __attribute__ ((mode (__word__))) be used here?

Otherwise OK.

Thanks,
Uros.

>  #if !__PIC__

> -register int k asm("%ebx");

> +register reg_type k asm("%ebx");

>  #elif __amd64

> -register int k asm("%r12");

> +register reg_type k asm("%r12");

>  #else

> -register int k asm("%esi");

> +register reg_type k asm("%esi");

>  #endif

>

>  void __attribute__((noinline))

> @@ -18,7 +22,7 @@ foo()

>

>  void test()

>  {

> -  int i;

> +  reg_type i;

>    for (i = 0; i < 10; i += k)

>      {

>        k = 0;

> @@ -28,7 +32,7 @@ void test()

>

>  int main()

>  {

> -  int old = k;

> +  reg_type old = k;

>    test();

>    k = old;

>    return 0;

>

> --

> Alexandre Oliva, freedom fighter  he/him   https://FSFLA.org/blogs/lxo

> Be the change, be Free!                 FSF Latin America board member

> GNU Toolchain Engineer                        Free Software Evangelist

> Hay que enGNUrecerse, pero sin perder la terGNUra jamás - Che GNUevara

>
Alexandre Oliva Sept. 3, 2019, 5:36 a.m. | #2
On Aug 24, 2019, Uros Bizjak <ubizjak@gmail.com> wrote:

> Can __attribute__ ((mode (__word__))) be used here?


Oh, nice, yes, thanks!

> Otherwise OK.


Here's what I'm installing.


for  gcc/testsuite/ChangeLog

	* gcc.target/i386/20020616-1.c: Preserve full register across
	main.
---
 gcc/testsuite/gcc.target/i386/20020616-1.c |   14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/gcc/testsuite/gcc.target/i386/20020616-1.c b/gcc/testsuite/gcc.target/i386/20020616-1.c
index 5641826b4837c..48dea27956ce2 100644
--- a/gcc/testsuite/gcc.target/i386/20020616-1.c
+++ b/gcc/testsuite/gcc.target/i386/20020616-1.c
@@ -2,12 +2,16 @@
 /* { dg-do run } */
 /* { dg-options "-O2" } */
 
+/* We need this type to be as wide as the register chosen below, so
+   that, when we preserve it across main, we preserve all of it.  */
+typedef int __attribute__ ((mode (__word__))) reg_type;
+
 #if !__PIC__
-register int k asm("%ebx");
+register reg_type k asm("%ebx");
 #elif __amd64
-register int k asm("%r12");
+register reg_type k asm("%r12");
 #else
-register int k asm("%esi");
+register reg_type k asm("%esi");
 #endif
 
 void __attribute__((noinline))
@@ -18,7 +22,7 @@ foo()
 
 void test()
 {
-  int i;
+  reg_type i;
   for (i = 0; i < 10; i += k)
     {
       k = 0;
@@ -28,7 +32,7 @@ void test()
 
 int main()
 {
-  int old = k;
+  reg_type old = k;
   test();
   k = old;
   return 0;


-- 
Alexandre Oliva, freedom fighter  he/him   https://FSFLA.org/blogs/lxo
Be the change, be Free!       FSF.org & FSF Latin America board member
GNU Toolchain Engineer                        Free Software Evangelist
Hay que enGNUrecerse, pero sin perder la terGNUra jamás - Che GNUevara

Patch

diff --git a/gcc/testsuite/gcc.target/i386/20020616-1.c b/gcc/testsuite/gcc.target/i386/20020616-1.c
index 5641826b4837..3b8cf8e41783 100644
--- a/gcc/testsuite/gcc.target/i386/20020616-1.c
+++ b/gcc/testsuite/gcc.target/i386/20020616-1.c
@@ -2,12 +2,16 @@ 
 /* { dg-do run } */
 /* { dg-options "-O2" } */
 
+/* We need this type to be as wide as the register chosen below, so
+   that, when we preserve it across main, we preserve all of it.  */
+typedef long reg_type;
+
 #if !__PIC__
-register int k asm("%ebx");
+register reg_type k asm("%ebx");
 #elif __amd64
-register int k asm("%r12");
+register reg_type k asm("%r12");
 #else
-register int k asm("%esi");
+register reg_type k asm("%esi");
 #endif
 
 void __attribute__((noinline))
@@ -18,7 +22,7 @@  foo()
 
 void test()
 {
-  int i;
+  reg_type i;
   for (i = 0; i < 10; i += k)
     {
       k = 0;
@@ -28,7 +32,7 @@  void test()
 
 int main()
 {
-  int old = k;
+  reg_type old = k;
   test();
   k = old;
   return 0;