[PATCH] Fix tests that require IBM 128-bit long double

Michael Meissner meissner@linux.ibm.com
Fri Aug 13 04:09:24 GMT 2021


Fix tests that require IBM 128-bit long double

I posted an earlier version of this patch on July 7th, and Segher had some
comments about it on July 14th.  This is a revised version of the patch

 * My patch: Message-ID: <20210707195837.GA28511@ibm-toto.the-meissners.org>
 * Seger's reply: Message-ID: <20210714223208.GF1583@gate.crashing.org>

This patch adds 3 more selections to target-supports.exp to see if we can
specify 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 just reverified that this patch still works on a little endian power9 system
running Linux.

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.

Compared the to last version that I posted, I simplified the fucntion names
(eliminating the 'ppc_' and 'override_' parts).  I have changed the length
parameter from using sizeof to just using 16.  I removed the #if code in the
tests.  I changed the comments.

I did not remove the void * casts in calling memcmp, because not having those
casts will cause the test to fail.  This is because the variables are declared
volatile, and GCC now complains that you are discarding the volatile in doing
the call.  Having this warning makes the test fail.

Can I check this patch into the master branch?

2021-08-12  Michael Meissner  <meissner@linux.ibm.com>

gcc/testsuite/
	PR target/94630
	* gcc.target/powerpc/pr70117.c: Specify that we need the long double
	type to be IBM 128-bit.  Remove the code to use __ibm128.
	* c-c++-common/dfp/convert-bfp-11.c: Specify that we need the long
	double type to be IBM 128-bit.  Run the test at -O2 optimization.
	* lib/target-supports.exp (add_options_for_long_double_ibm128): New
	function.
	(check_effective_target_long_double_ibm128): New function.
	(add_options_for_long_double_ieee128): New function.
	(check_effective_target_long_double_ieee128): New function.
	(add_options_for_long_double_64bit): New function.
	(check_effective_target_long_double_64bit): New function.
---
 .../c-c++-common/dfp/convert-bfp-11.c         |  20 ++--
 gcc/testsuite/gcc.target/powerpc/pr70117.c    |  24 ++--
 gcc/testsuite/lib/target-supports.exp         | 110 ++++++++++++++++++
 3 files changed, 130 insertions(+), 24 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..c09c8342bbb 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 +1,16 @@
-/* { dg-skip-if "" { ! "powerpc*-*-linux*" } } */
+/* { dg-require-effective-target dfp } */
 
-/* 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 need 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.  */
+
+/* { dg-require-effective-target long_double_ibm128 } */
+/* { dg-options "-O2" } */
+/* { dg-add-options long_double_ibm128 } */
+
+/* Test decimal float conversions to and from IBM 128-bit long double.   */
 
 #include "convert.h"
 
@@ -36,9 +43,6 @@ 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..4a51f583157 100644
--- a/gcc/testsuite/gcc.target/powerpc/pr70117.c
+++ b/gcc/testsuite/gcc.target/powerpc/pr70117.c
@@ -1,26 +1,18 @@
-/* { 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 long_double_ibm128 } */
+/* { dg-options "-std=c99 -O2" } */
+/* { dg-add-options long_double_ibm128 } */
 
 #include <float.h>
 
-#if defined(__LONG_DOUBLE_IEEE128__)
-/* If long double is IEEE 128-bit, we need to use the __ibm128 type instead of
-   long double.  We can't use __ibm128 on systems that don't support IEEE
-   128-bit floating point, because the type is not enabled on those
-   systems.  */
-#define LDOUBLE __ibm128
-
-#elif defined(__LONG_DOUBLE_IBM128__)
-#define LDOUBLE long double
-
-#else
-#error "long double must be either IBM 128-bit or IEEE 128-bit"
+#ifndef __LONG_DOUBLE_IBM128__
+#error "long double must be IBM 128-bit"
 #endif
 
 union gl_long_double_union
 {
   struct { double hi; double lo; } dd;
-  LDOUBLE ld;
+  long double ld;
 };
 
 /* This is gnulib's LDBL_MAX which, being 107 bits in precision, is
@@ -36,7 +28,7 @@ volatile double dnan = 0.0/0.0;
 int
 main (void)
 {
-  LDOUBLE ld;
+  long double ld;
 
   ld = gl_LDBL_MAX.ld;
   if (__builtin_isinf (ld))
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 44465b14b06..09664e88537 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -2360,6 +2360,116 @@ proc check_effective_target_ppc_ieee128_ok { } {
     }]
 }
 
+# Return the appropriate options to specify that long double uses the IBM
+# 128-bit format on PowerPC.
+
+proc add_options_for_long_double_ibm128 { flags } {
+    if { [istarget powerpc*-*-*] } {
+	return "$flags -mlong-double-128 -Wno-psabi -mabi=ibmlongdouble"
+    }
+    return "$flags"
+}
+
+# Check if GCC and GLIBC supports explicitly specifying that the long double
+# format uses the IBM 128-bit extended double format.  Under little endian
+# PowerPC Linux, you need GLIBC 2.32 or later to be able to use a different
+# long double format for running a program than the system default.
+
+proc check_effective_target_long_double_ibm128 { } {
+    return [check_runtime_nocache long_double_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 (sizeof (long double) != 16)
+	    return 1;
+	  b = one + two;
+	  if (memcmp ((void *)&a, (void *)&b, 16) != 0)
+	    return 1;
+	  sprintf (buffer, "%lg", b);
+	  return strcmp (buffer, "3") != 0;
+	}
+    } [add_options_for_long_double_ibm128 ""]]
+}
+
+# Return the appropriate options to specify that long double uses the IBM
+# 128-bit format on PowerPC.
+proc add_options_for_long_double_ieee128 { flags } {
+    if { [istarget powerpc*-*-*] } {
+	return "$flags -mlong-double-128 -Wno-psabi -mabi=ieeelongdouble"
+    }
+    return "$flags"
+}
+
+# Check if GCC and GLIBC supports explicitly specifying that the long double
+# format uses the IEEE 128-bit format.  Under little endian PowerPC Linux, you
+# need GLIBC 2.32 or later to be able to use a different long double format for
+# running a program than the system default.
+
+proc check_effective_target_long_double_ieee128 { } {
+    return [check_runtime_nocache long_double_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 (sizeof (long double) != 16)
+	    return 1;
+	  b = one + two;
+	  if (memcmp ((void *)&a, (void *)&b, 16) != 0)
+	    return 1;
+	  sprintf (buffer, "%lg", b);
+	  return strcmp (buffer, "3") != 0;
+	}
+    }  [add_options_for_long_double_ieee128 ""]]
+}
+
+# Return the appropriate options to specify that long double uses the IEEE
+# 64-bit format on PowerPC.
+
+proc add_options_for_long_double_64bit { flags } {
+    if { [istarget powerpc*-*-*] } {
+	return "$flags -mlong-double-64"
+    }
+    return "$flags"
+}
+
+# Check if GCC and GLIBC supports explicitly specifying that the long double
+# format uses the IEEE 64-bit.  Under little endian PowerPC Linux, you need
+# GLIBC 2.32 or later to be able to use a different long double format for
+# running a program than the system default.
+
+proc check_effective_target_long_double_64bit { } {
+    return [check_runtime_nocache long_double_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 (sizeof (long double) != 8)
+	    return 1;
+	  b = one + two;
+	  if (memcmp ((void *)&a, (void *)&b, 16) != 0)
+	    return 1;
+	  sprintf (buffer, "%lg", b);
+	  return strcmp (buffer, "3") != 0;
+	}
+    }  [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


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