Fix implementation of iamax_sse.S as reported in #2116.

The was a typo in iamax_sse.S where one of the comparison
was cmpeqps instead of cmpeqss. That misdetected index
for sequences where the minimum value was 0.

kernel/x86_64/KERNEL

@@ -171,7 +171,7 @@ IXAMAXKERNEL = izamax.S
 endif
 
 ifndef ISAMINKERNEL
-ISAMINKERNEL = iamax.S
+ISAMINKERNEL = iamax_sse.S
 endif
 
 ifndef IDAMINKERNEL
@@ -207,7 +207,7 @@ IQMAXKERNEL = iamax.S
 endif
 
 ifndef ISMINKERNEL
-ISMINKERNEL = iamax.S
+ISMINKERNEL = iamax_sse.S
 endif
 
 ifndef IDMINKERNEL

kernel/x86_64/iamax_sse.S

@@ -36,10 +36,6 @@
 /* or implied, of The University of Texas at Austin.                 */
 /*********************************************************************/
 
-/* This kernel was found to give wrong results when used for ISMIN/ISAMIN
-   with increment != 1, although it appears to be correct for corresponding
-   MAX operations. See issue 2116 */
-
 #define ASSEMBLER
 #include "common.h"
 
@@ -863,7 +859,7 @@
 #ifdef USE_ABS
 	andps	 %xmm15, %xmm5
 #endif
-	cmpeqps	%xmm0, %xmm5
+	cmpeqss	%xmm0, %xmm5
 
 	movss	0 * SIZE(X), %xmm6
 	addq	INCX, X

utest/CMakeLists.txt

@@ -7,6 +7,7 @@ else ()
   set(OpenBLAS_utest_src
     utest_main.c
     test_amax.c
+    test_ismin.c
     test_rotmg.c
     test_rot.c
     test_axpy.c

utest/Makefile

@@ -11,7 +11,7 @@ UTESTBIN=openblas_utest
 
 include $(TOPDIR)/Makefile.system
 
-OBJS=utest_main.o test_amax.o test_rotmg.o test_axpy.o test_dotu.o test_dsdot.o test_swap.o test_rot.o
+OBJS=utest_main.o test_amax.o test_ismin.o test_rotmg.o test_axpy.o test_dotu.o test_dsdot.o test_swap.o test_rot.o
 #test_rot.o test_swap.o test_axpy.o test_dotu.o test_dsdot.o test_fork.o
 
 ifneq ($(NO_LAPACK), 1)

utest/test_ismin.c

@@ -0,0 +1,89 @@
+/*****************************************************************************
+Copyright (c) 2020, The OpenBLAS Project
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   1. Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+   2. Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in
+      the documentation and/or other materials provided with the
+      distribution.
+   3. Neither the name of the OpenBLAS project nor the names of
+      its contributors may be used to endorse or promote products
+      derived from this software without specific prior written
+      permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+**********************************************************************************/
+
+#include "openblas_utest.h"
+
+#define ELEMENTS 50
+#define INCREMENT 2
+
+CTEST(ismin, positive_step_2){
+	blasint i;
+  blasint N = ELEMENTS, inc = INCREMENT;
+  float x[ELEMENTS * INCREMENT];
+  for (i = 0; i < N * inc; i ++) {
+    x[i] = i + 1000;
+  }
+
+  x[8 * inc] = 0;
+  blasint index = BLASFUNC(ismin)(&N, x, &inc);
+  ASSERT_EQUAL(9, index);
+}
+
+CTEST(ismin, negative_step_2){
+	blasint i;
+  blasint N = ELEMENTS, inc = INCREMENT;
+  float x[ELEMENTS * INCREMENT];
+  for (i = 0; i < N * inc; i ++) {
+    x[i] = - i - 1000;
+  }
+
+  x[8 * inc] = -123456.0f;
+  blasint index = BLASFUNC(ismin)(&N, x, &inc);
+  ASSERT_EQUAL(9, index);
+}
+
+CTEST(ismax, positive_step_2){
+	blasint i;
+  blasint N = ELEMENTS, inc = INCREMENT;
+  float x[ELEMENTS * INCREMENT];
+  for (i = 0; i < N * inc; i ++) {
+    x[i] = i + 1000;
+  }
+
+  x[8 * inc] = 123456.0f;
+  blasint index = BLASFUNC(ismax)(&N, x, &inc);
+  ASSERT_EQUAL(9, index);
+}
+
+CTEST(ismax, negative_step_2){
+	blasint i;
+  blasint N = ELEMENTS, inc = INCREMENT;
+  float x[ELEMENTS * INCREMENT];
+  for (i = 0; i < N * inc; i ++) {
+    x[i] = - i - 1000;
+  }
+
+  x[8 * inc] = 0;
+  blasint index = BLASFUNC(ismax)(&N, x, &inc);
+  ASSERT_EQUAL(9, index);
+}