Merge pull request OpenMathLib#4320 from ChipKerchner/fixOldGCCPower

Fix older versions of gcc - missing __has_builtin, cpuid and no support of P10.

Makefile.power

@@ -11,7 +11,19 @@ endif
 
 ifeq ($(CORE), POWER10)
 ifneq ($(C_COMPILER), PGI)
+ifeq ($(C_COMPILER), GCC))
+ifeq ($(GCCVERSIONGTEQ10), 1)
 CCOMMON_OPT += -Ofast -mcpu=power10 -mtune=power10 -mvsx -fno-fast-math
+else ifneq ($(GCCVERSIONGT4), 1)
+$(warning your compiler is too old to fully support POWER9, getting a newer version of gcc is recommended)
+CCOMMON_OPT += -Ofast -mcpu=power8 -mtune=power8 -mvsx -fno-fast-math
+else
+$(warning your compiler is too old to fully support POWER10, getting a newer version of gcc is recommended)
+CCOMMON_OPT += -Ofast -mcpu=power9 -mtune=power9 -mvsx -fno-fast-math
+endif
+else
+CCOMMON_OPT += -Ofast -mcpu=power10 -mtune=power10 -mvsx -fno-fast-math
+endif
 ifeq ($(F_COMPILER), IBM)
 FCOMMON_OPT += -O2 -qrecur -qnosave -qarch=pwr10 -qtune=pwr10 -qfloat=nomaf -qzerosize
 else

driver/others/dynamic_power.c

@@ -66,8 +66,7 @@ static int cpuid(void)
 #endif
     return CPU_UNKNOWN;
 }
-#else
-#if defined(C_PGI) || defined(__clang__)
+#elif defined(C_PGI) || defined(__clang__)
 /*
  * NV HPC compilers do not yet implement __builtin_cpu_is().
  * Fake a version here for use in the CPU detection code below.
@@ -196,13 +195,21 @@ static int cpuid(void)
 	cpu_type = pvrPOWER[i].cpu_type;
 	return (int)(cpu_type);
 }
-#endif  /* C_PGI */
+#elif !defined(__BUILTIN_CPU_SUPPORTS__)
+static int cpuid(void)
+{
+    return CPU_UNKNOWN;
+}
 #endif  /* _AIX */
 
 #ifndef __BUILTIN_CPU_SUPPORTS__
 #include <string.h>
 
-#if defined(_AIX) || (defined(__has_builtin) && !__has_builtin(__builtin_cpu_is))
+#ifndef __has_builtin
+#define __has_builtin(x)   0
+#endif
+
+#if defined(_AIX) || !__has_builtin(__builtin_cpu_is)
 static int __builtin_cpu_is(const char *arg)
 {
     static int ipinfo = -1;
@@ -227,7 +234,7 @@ static int __builtin_cpu_is(const char *arg)
 }
 #endif
 
-#if defined(_AIX) || (defined(__has_builtin) && !__has_builtin(__builtin_cpu_supports))
+#if defined(_AIX) || !__has_builtin(__builtin_cpu_supports)
 static int __builtin_cpu_supports(const char *arg)
 {
     return 0;