s390x/DYNAMIC_ARCH: pass supported arch levels from Makefile to run-time code

... instead of duplicating the (old) mechanism from the Makefile that
aimed to derive supported architecture generations from the gcc
version.

To enable builds with DYNAMIC_ARCH with older compiler releases, the
Makefile and drivers/other/dynamic_arch.c need a common view of the
architecture support built into the library.

We follow the notation from x86 when used with DYNAMIC_LIST, where
defines DYN_<ARCH NAME> denote support for a given generation to be
built in. Since there are far fewer architecture generations in OpenBLAS
for s390x, that does not bloat command lines too much.

Signed-off-by: Marius Hillenbrand <mhillen@linux.ibm.com>

Makefile.system

@@ -606,6 +606,7 @@ ZARCH_CC_SUPPORTS_Z13=$(shell $(CC) -march=z13 $(ZARCH_TEST_COMPILE) && echo 1)
 
 ifeq ($(or $(ZARCH_CC_SUPPORTS_ARCH11), $(ZARCH_CC_SUPPORTS_Z13)), 1)
 DYNAMIC_CORE += Z13
+CCOMMON_OPT += -DDYN_Z13
 else
 $(info OpenBLAS: Not building Z13 kernels because the compiler $(CC) does not support it)
 endif
@@ -615,6 +616,7 @@ ZARCH_CC_SUPPORTS_ARCH12=$(shell $(CC) -march=arch12 $(ZARCH_TEST_COMPILE) && ec
 ZARCH_CC_SUPPORTS_Z14=$(shell $(CC) -march=z14 $(ZARCH_TEST_COMPILE) && echo 1)
 ifeq ($(or $(ZARCH_CC_SUPPORTS_ARCH12), $(ZARCH_CC_SUPPORTS_Z14)), 1)
 DYNAMIC_CORE += Z14
+CCOMMON_OPT += -DDYN_Z14
 else
 $(info OpenBLAS: Not building Z14 kernels because the compiler $(CC) does not support it)
 endif

driver/others/dynamic_zarch.c

@@ -1,18 +1,6 @@
 #include "common.h"
 #include <stdbool.h>
 
-// Gate kernels for z13 and z14 on gcc version
-#if (__GNUC__ == 5 && __GNUC_MINOR__ >= 2) || __GNUC__ >= 6 ||           \
-    /* RHEL 7 since 7.3: */                                              \
-    (__GNUC__ == 4 && __GNUC_MINOR__ == 8 && __GNUC_PATCHLEVEL__ == 5 && \
-     __GNUC_RH_RELEASE__ >= 11)
-#define HAVE_Z13_SUPPORT
-#endif
-
-#if __GNUC__ >= 7
-#define HAVE_Z14_SUPPORT
-#endif
-
 // Guard the use of getauxval() on glibc version >= 2.16
 #ifdef __GLIBC__
 #include <features.h>
@@ -47,10 +35,10 @@ static unsigned long get_hwcap(void) {
 #endif // __GLIBC
 
 extern gotoblas_t gotoblas_ZARCH_GENERIC;
-#ifdef HAVE_Z13_SUPPORT
+#ifdef DYN_Z13
 extern gotoblas_t gotoblas_Z13;
 #endif
-#ifdef HAVE_Z14_SUPPORT
+#ifdef DYN_Z14
 extern gotoblas_t gotoblas_Z14;
 #endif
 
@@ -66,10 +54,10 @@ static char* corename[] = {
 };
 
 char* gotoblas_corename(void) {
-#ifdef HAVE_Z13_SUPPORT
+#ifdef DYN_Z13
 	if (gotoblas == &gotoblas_Z13)	return corename[1];
 #endif
-#ifdef HAVE_Z14_SUPPORT
+#ifdef DYN_Z14
 	if (gotoblas == &gotoblas_Z14)	return corename[2];
 #endif
 	if (gotoblas == &gotoblas_ZARCH_GENERIC) return corename[3];
@@ -89,15 +77,15 @@ static gotoblas_t* get_coretype(void) {
 
 	unsigned long hwcap __attribute__((unused)) = get_hwcap();
 
+#ifdef DYN_Z14
 	// z14 and z15 systems: exploit Vector Facility (SIMD) and
 	// Vector-Enhancements Facility 1 (float SIMD instructions), if present.
-#ifdef HAVE_Z14_SUPPORT
 	if ((hwcap & HWCAP_S390_VX) && (hwcap & HWCAP_S390_VXE))
 		return &gotoblas_Z14;
 #endif
 
+#ifdef DYN_Z13
 	// z13: Vector Facility (SIMD for double)
-#ifdef HAVE_Z13_SUPPORT
 	if (hwcap & HWCAP_S390_VX)
 		return &gotoblas_Z13;
 #endif
@@ -123,19 +111,27 @@ static gotoblas_t* force_coretype(char* coretype) {
 		}
 	}
 
-	switch (found)
-	{
-#ifdef HAVE_Z13_SUPPORT
-	case  1: return (&gotoblas_Z13);
+	if (found == 1) {
+#ifdef DYN_Z13
+		return &gotoblas_Z13;
+#else
+		openblas_warning(1, "Z13 support not compiled in");
+		return NULL;
 #endif
-#ifdef HAVE_Z14_SUPPORT
-	case  2: return (&gotoblas_Z14);
+	} else if (found == 2) {
+#ifdef DYN_Z14
+		return &gotoblas_Z14;
+#else
+		openblas_warning(1, "Z14 support not compiled in");
+		return NULL;
 #endif
-	case  3: return (&gotoblas_ZARCH_GENERIC);
-	default: return NULL;
+	} else if (found == 3) {
+		return &gotoblas_ZARCH_GENERIC;
 	}
+
 	snprintf(message, 128, "Core not found: %s\n", coretype);
 	openblas_warning(1, message);
+	return NULL;
 }
 
 void gotoblas_dynamic_init(void) {