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authorPaul E. Murphy <murphyp@linux.vnet.ibm.com>2020-02-07 14:08:23 -0600
committerPaul E. Murphy <murphyp@linux.vnet.ibm.com>2020-04-30 08:52:08 -0500
commit50545f5aa0111c1e7f8917348490907d1a1e1f9b (patch)
tree69f10aa5ec7f6c8ea2188aec952d7c2907873274 /NEWS
parente2239af353b053b9c645e396b13bce8688f9d615 (diff)
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powerpc64le: raise GCC requirement to 7.4 for long double transition
Add compiler feature tests to ensure we can build ieee128 long double.
These test for -mabi=ieeelongdouble, -mno-gnu-attribute, and -Wno-psabi.

Likewise, verify some compiler bugs have been addressed.  These aren't
helpful for building glibc, but may cause test failures when testing
the new long double.  See notes below from Raji.

On powerpc64le, some older compiler versions give error for the function
signbit() for 128-bit floating point types.  This is fixed by PR83862
in gcc 8.0 and backported to gcc6 and gcc7.  This patch adds a test
to check compiler version to avoid compiler errors during make check.

Likewise, test for -mno-gnu-attribute support which was

On powerpc64le, a few files are built on IEEE long double mode
(-mabi=ieeelongdouble), whereas most are built on IBM long double mode
(-mabi=ibmlongdouble, the default for -mlong-double-128).  Since binutils
2.31, linking object files with different long double modes causes
errors similar to:

  ld: libc_pic.a(s_isinfl.os) uses IBM long double,
      libc_pic.a(ieee128-qefgcvt.os) uses IEEE long double.
  collect2: error: ld returned 1 exit status
  make[2]: *** [../Makerules:649: libc_pic.os] Error 1

The warnings are fair and correct, but in order for glibc to have
support for both long double modes on powerpc64le, they have to be
ignored.  This can be accomplished with the use of -mno-gnu-attribute
option when building the few files that require IEEE long double mode.

However, -mno-gnu-attribute is not available in GCC 6, the minimum
version required to build glibc, so this patch adds a test for this
feature in powerpc64le builds, and fails early if it's not available.

Co-Authored-By: Rajalakshmi Srinivasaraghavan  <raji@linux.vnet.ibm.com>
Co-Authored-By: Gabriel F. T. Gomes <gabrielftg@linux.ibm.com>
Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
Diffstat (limited to 'NEWS')
-rw-r--r--NEWS3
1 files changed, 2 insertions, 1 deletions
diff --git a/NEWS b/NEWS
index f58436c91a..e60f83a947 100644
--- a/NEWS
+++ b/NEWS
@@ -32,7 +32,8 @@ Deprecated and removed features, and other changes affecting compatibility:
 
 Changes to build and runtime requirements:
 
-  [Add changes to build and runtime requirements here]
+* powerpc64le requires GCC 7.4 or newer.  This is required for supporting
+  long double redirects.
 
 Security related changes: