gnu: openblas: Fix build on i686.

* gnu/packages/patches/openblas-fix-tests-i686.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.
* gnu/packages/maths.scm (openblas)[native-inputs]: Add it.
[arguments]: Add phase to apply it on i686 systems only.

gnu/local.mk

@@ -967,6 +967,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/omake-fix-non-determinism.patch	\
   %D%/packages/patches/ola-readdir-r.patch			\
   %D%/packages/patches/opencascade-oce-glibc-2.26.patch		\
+  %D%/packages/patches/openblas-fix-tests-i686.patch		\
   %D%/packages/patches/openexr-missing-samples.patch		\
   %D%/packages/patches/openfoam-4.1-cleanup.patch			\
   %D%/packages/patches/openldap-CVE-2017-9287.patch		\

gnu/packages/maths.scm

@@ -2836,6 +2836,16 @@ parts of it.")
        #:phases
        (modify-phases %standard-phases
          (delete 'configure)
+         ;; Conditionally apply a patch on i686 to avoid rebuilding
+         ;; all architectures.  FIXME: This should be moved to the
+         ;; (source (patches ...)) field in the next rebuild cycle.
+         ,@(if (string-prefix? "i686" (or (%current-target-system)
+                                          (%current-system)))
+               `((add-after 'unpack 'fix-tests
+                   (lambda* (#:key inputs #:allow-other-keys)
+                     (invoke "patch" "-p1"
+                             "--input" (assoc-ref inputs "i686-fix-tests.patch")))))
+               '())
          (add-before 'build 'set-extralib
            (lambda* (#:key inputs #:allow-other-keys)
              ;; Get libgfortran found when building in utest.
@@ -2847,6 +2857,11 @@ parts of it.")
      `(("fortran-lib" ,gfortran "lib")))
     (native-inputs
      `(("cunit" ,cunit)
+       ,@(if (string-prefix? "i686" (or (%current-target-system)
+                                        (%current-system)))
+             `(("i686-fix-tests.patch"
+                ,(search-patch "openblas-fix-tests-i686.patch")))
+             '())
        ("fortran" ,gfortran)
        ("perl" ,perl)))
     (home-page "http://www.openblas.net/")

gnu/packages/patches/openblas-fix-tests-i686.patch

@@ -0,0 +1,35 @@
+Fix a test failure on some i686 systems:
+
+https://github.com/xianyi/OpenBLAS/issues/1575
+
+This patch is a squashed version of these commits:
+
+https://github.com/xianyi/OpenBLAS/pull/1583
+
+diff --git a/kernel/x86/KERNEL.NEHALEM b/kernel/x86/KERNEL.NEHALEM
+index 835520ef..65b03ae5 100644
+--- a/kernel/x86/KERNEL.NEHALEM
++++ b/kernel/x86/KERNEL.NEHALEM
+@@ -1,3 +1 @@
+ include $(KERNELDIR)/KERNEL.PENRYN
+-SSWAPKERNEL  = ../arm/swap.c
+-DSWAPKERNEL  = ../arm/swap.c
+diff --git a/kernel/x86/swap.S b/kernel/x86/swap.S
+index 54b00b33..e30c2789 100644
+--- a/kernel/x86/swap.S
++++ b/kernel/x86/swap.S
+@@ -138,6 +138,14 @@
+ /* INCX != 1 or INCY != 1 */
+ 
+ .L14:
++	cmpl	$0, %ebx
++	jne	.L141
++	cmpl	$0, %ecx
++	jne	.L141
++/* INCX == 0 and INCY == 0 */
++	jmp	.L27
++
++.L141:
+ 	movl	%edx, %eax
+ 	sarl	$2,   %eax
+ 	jle	.L28