[PATCH] Fix long double tests when default long double is not IBM.

[Michael Meissner <meissner@linux.ibm.com>]

[PATCH] Fix long double tests when default long double is not IBM.

This patch adds 3 more selections to target-supports.exp to see if we can force
the compiler to use a particular long double format (IEEE 128-bit, IBM extended
double, 64-bit), and the library support will track the changes for the long
double.  This is needed because two of the tests in the test suite use long
double, and they are actually testing IBM extended double.

This patch also forces the two tests that explicitly require long double
to use the IBM double-double encoding to explicitly run the test.  This
requires GLIBC 2.32 or greater in order to do the switch.

I have run tests on a little endian power9 system with 3 compilers.  There were
no regressions with these patches, and the two tests in the following patches
now work if the default long double is not IBM 128-bit:

    *	One compiler used the default IBM 128-bit format;
    *	One compiler used the IEEE 128-bit format; (and)
    *	One compiler used 64-bit long doubles.

I have also tested compilers on a big endian power8 system with a compiler
defaulting to power8 code generation and another with the default cpu
set.  There were no regressions.

Can I check this patch into the master branch?

I have done bootstrap builds with this patch on the following 4 systems:
    1)	power9 running LE Linux using --with-cpu=power9 with long double == IBM
    2)	power9 running LE Linux using --with-cpu=power9 with long double == IEEE
    3)	power8 running BE Linux using --with-cpu=power8, testing both
	32/64-bit.
    4)	power10 prototype running LE Linux using --with-cpu=power10.

There were no regressions to the tests, and the two test cases that previously
failed with I ran the compiler defaulting to long double using IEEE 128-bit now
passed.  Can I check these patches into trunk branch for GCC 12?

I would like to check these patches into GCC 11 after a cooling off period, but
I can also not do the backport if desired.

gcc/testsuite/
2021-05-18  Michael Meissner  <meissner@linux.ibm.com>

	PR target/70117
	* gcc.target/powerpc/pr70117.c: Force the long double type to use
	the IBM 128-bit format.
	* c-c++-common/dfp/convert-bfp-11.c: Force using IBM 128-bit long
	double.  Remove check for 64-bit long double.
	* lib/target-supports.exp
	(add_options_for_ppc_long_double_override_ibm128): New function.
	(check_effective_target_ppc_long_double_override_ibm128): New
	function.
	(add_options_for_ppc_long_double_override_ieee128): New function.
	(check_effective_target_ppc_long_double_override_ieee128): New
	function.
	(add_options_for_ppc_long_double_override_64bit): New function.
	(check_effective_target_ppc_long_double_override_64bit): New
	function.
---
 .../c-c++-common/dfp/convert-bfp-11.c         |  18 +--
 gcc/testsuite/gcc.target/powerpc/pr70117.c    |   6 +-
 gcc/testsuite/lib/target-supports.exp         | 107 ++++++++++++++++++
 3 files changed, 121 insertions(+), 10 deletions(-)

diff --git a/gcc/testsuite/c-c++-common/dfp/convert-bfp-11.c b/gcc/testsuite/c-c++-common/dfp/convert-bfp-11.c
index 95c433d2c24..35da07d1fa4 100644
--- a/gcc/testsuite/c-c++-common/dfp/convert-bfp-11.c
+++ b/gcc/testsuite/c-c++-common/dfp/convert-bfp-11.c
@@ -1,9 +1,14 @@
-/* { dg-skip-if "" { ! "powerpc*-*-linux*" } } */
+/* { dg-require-effective-target dfp } */
+/* { dg-require-effective-target ppc_long_double_override_ibm128 } */
+/* { dg-add-options ppc_long_double_override_ibm128 } */
 
-/* Test decimal float conversions to and from IBM 128-bit long double. 
-   Checks are skipped at runtime if long double is not 128 bits.
-   Don't force 128-bit long doubles because runtime support depends
-   on glibc.  */
+/* We force the long double type to be IBM 128-bit because the CONVERT_TO_PINF
+   tests will fail if we use IEEE 128-bit floating point.  This is due to IEEE
+   128-bit having a larger exponent range than IBM 128-bit extended double.  So
+   tests that would generate an infinity with IBM 128-bit will generate a
+   normal number with IEEE 128-bit.  */
+
+/* Test decimal float conversions to and from IBM 128-bit long double.   */
 
 #include "convert.h"
 
@@ -36,9 +41,6 @@ CONVERT_TO_PINF (312, tf, sd, 1.6e+308L, d32)
 int
 main ()
 {
-  if (sizeof (long double) != 16)
-    return 0;
-
   convert_101 ();
   convert_102 ();
 
diff --git a/gcc/testsuite/gcc.target/powerpc/pr70117.c b/gcc/testsuite/gcc.target/powerpc/pr70117.c
index 3bbd2c595e0..8a5fad1dee0 100644
--- a/gcc/testsuite/gcc.target/powerpc/pr70117.c
+++ b/gcc/testsuite/gcc.target/powerpc/pr70117.c
@@ -1,5 +1,7 @@
-/* { dg-do run { target { powerpc*-*-linux* powerpc*-*-darwin* powerpc*-*-aix* rs6000-*-* } } } */
-/* { dg-options "-std=c99 -mlong-double-128 -O2" } */
+/* { dg-do run } */
+/* { dg-require-effective-target ppc_long_double_override_ibm128 } */
+/* { dg-options "-std=c99 -O2" } */
+/* { dg-add-options ppc_long_double_override_ibm128 } */
 
 #include <float.h>
 
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 8192da5ec9f..c1f2c4ff96a 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -2360,6 +2360,113 @@ proc check_effective_target_ppc_ieee128_ok { } {
     }]
 }
 
+# Check if we can explicitly override the long double format to use the IBM
+# 128-bit extended double format, and GLIBC supports doing this override by
+# switching the sprintf to handle IBM 128-bit long double.
+
+proc add_options_for_ppc_long_double_override_ibm128 { flags } {
+    if { [istarget powerpc*-*-*] } {
+	return "$flags -mlong-double-128 -Wno-psabi -mabi=ibmlongdouble"
+    }
+    return "$flags"
+}
+
+proc check_effective_target_ppc_long_double_override_ibm128 { } {
+    return [check_runtime_nocache ppc_long_double_override_ibm128 {
+	#include <string.h>
+	#include <stdio.h>
+	volatile __ibm128 a = (__ibm128) 3.0;
+	volatile long double one = 1.0L;
+	volatile long double two = 2.0L;
+	volatile long double b;
+	char buffer[20];
+	int main()
+	{
+	  #if !defined(_ARCH_PPC) || !defined(__LONG_DOUBLE_IBM128__)
+	    return 1;
+	  #else
+	    b = one + two;
+	    if (memcmp ((void *)&a, (void *)&b, sizeof (long double)) != 0)
+	      return 1;
+	    sprintf (buffer, "%lg", b);
+	    return strcmp (buffer, "3") != 0;
+	  #endif
+	}
+    } [add_options_for_ppc_long_double_override_ibm128 ""]]
+}
+
+# Check if we can explicitly override the long double format to use the IEEE
+# 128-bit format, and GLIBC supports doing this override by switching the
+# sprintf to handle IEEE 128-bit long double.
+
+proc add_options_for_ppc_long_double_override_ieee128 { flags } {
+    if { [istarget powerpc*-*-*] } {
+	return "$flags -mlong-double-128 -Wno-psabi -mabi=ieeelongdouble"
+    }
+    return "$flags"
+}
+
+proc check_effective_target_ppc_long_double_override_ieee128 { } {
+    return [check_runtime_nocache ppc_long_double_override_ieee128 {
+	#include <string.h>
+	#include <stdio.h>
+	volatile _Float128 a = 3.0f128;
+	volatile long double one = 1.0L;
+	volatile long double two = 2.0L;
+	volatile long double b;
+	char buffer[20];
+	int main()
+	{
+	  #if !defined(_ARCH_PPC) || !defined(__LONG_DOUBLE_IEEE128__)
+	    return 1;
+	  #else
+	    b = one + two;
+	    if (memcmp ((void *)&a, (void *)&b, sizeof (long double)) != 0)
+	      return 1;
+	    sprintf (buffer, "%lg", b);
+	    return strcmp (buffer, "3") != 0;
+	  #endif
+	}
+    }  [add_options_for_ppc_long_double_override_ieee128 ""]]
+}
+
+# Check if we can explicitly override the long double format to use 64-bit
+# floating point, and GLIBC supports doing this override by switching the
+# sprintf to handle 64-bit long double.
+
+proc add_options_for_ppc_long_double_override_64bit { flags } {
+    if { [istarget powerpc*-*-*] } {
+	return "$flags -mlong-double-64"
+    }
+    return "$flags"
+}
+
+proc check_effective_target_ppc_long_double_override_64bit { } {
+    return [check_runtime_nocache ppc_long_double_override_64bit {
+	#include <string.h>
+	#include <stdio.h>
+	volatile double a = 3.0;
+	volatile long double one = 1.0L;
+	volatile long double two = 2.0L;
+	volatile long double b;
+	char buffer[20];
+	int main()
+	{
+	  #if !defined(_ARCH_PPC) || defined(__LONG_DOUBLE_128__)
+	    return 1;
+	  #else
+	    if (sizeof (long double) != sizeof (double))
+	      return 1;
+	    b = one + two;
+	    if (memcmp ((void *)&a, (void *)&b, sizeof (long double)) != 0)
+	      return 1;
+	    sprintf (buffer, "%lg", b);
+	    return strcmp (buffer, "3") != 0;
+	  #endif
+	}
+    }  [add_options_for_ppc_long_double_override_64bit ""]]
+}
+
 # Return 1 if the target supports executing VSX instructions, 0
 # otherwise.  Cache the result.
 
-- 
2.31.1

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.ibm.com, phone: +1 (978) 899-4797