build/run on machines that only have SSE2 with SIMDE (#303)

This allows the use of SIMDE library to emulate SSSE3/SSE4.2 instructions on SSE2-only (x86-64-v2) hardware.

---------

Co-authored-by: G.E <gregory.economou@vectorcamp.gr>
Co-authored-by: Konstantinos Margaritis <konstantinos@vectorcamp.gr>

src/hs_valid_platform.c

@@ -42,6 +42,7 @@ HS_PUBLIC_API
 hs_error_t HS_CDECL hs_valid_platform(void) {
     /* Hyperscan requires SSSE3, anything else is a bonus */
 #if !defined(VS_SIMDE_BACKEND) && (defined(ARCH_IA32) || defined(ARCH_X86_64))
+    // cppcheck-suppress knownConditionTrueFalse
     if (check_ssse3()) {
         return HS_SUCCESS;
     } else {

src/util/arch/x86/cpuid_inline.h

@@ -210,9 +210,13 @@ int check_avx512vbmi(void) {
 
 static inline
 int check_ssse3(void) {
+#if defined(VS_SIMDE_NATIVE) && (defined(ARCH_IA32) || defined(ARCH_X86_64))
+    return 1;
+#else
     unsigned int eax, ebx, ecx, edx;
     cpuid(1, 0, &eax, &ebx, &ecx, &edx);
     return !!(ecx & CPUID_SSSE3);
+#endif
 }
 
 static inline

src/util/simd_types.h

@@ -36,7 +36,9 @@
 #include "ue2common.h"
 
 #if defined(VS_SIMDE_BACKEND)
+#ifndef VECTORSIZE
 #define VECTORSIZE 16
+#endif
 #define SIMDE_ENABLE_NATIVE_ALIASES
 #if !defined(VS_SIMDE_NATIVE)
 #define SIMDE_NO_NATIVE