Fix support for X86 32-bit (#1842)

Signed-off-by: Mark Reid <[email protected]>

Author: markreidvfx

CMakeLists.txt

@@ -180,8 +180,11 @@ option(OCIO_USE_OIIO_FOR_APPS "Request OIIO to build apps (ociolutimage, ociocon
 
 
 if (NOT APPLE)
-    if ("${CMAKE_SYSTEM_PROCESSOR}" MATCHES "(AMD64|IA64|EM64T|X86|x86_64|i386|i686)")
+    if ("${CMAKE_SYSTEM_PROCESSOR}" MATCHES "(AMD64|IA64|EM64T|x86_64|X86|i386|i686)")
         # Intel-based architecture (not APPLE)
+        if ("${CMAKE_SYSTEM_PROCESSOR}" MATCHES "(X86|i386|i686)")
+            set(OCIO_ARCH_X86_32 1)
+        endif()
         set(OCIO_ARCH_X86 1)
         set(OCIO_BUILD_ENABLE_OPTIMIZATIONS_SSE ON)
         set(OCIO_BUILD_ENABLE_OPTIMIZATIONS_AVX ON)

src/OpenColorIO/CPUInfo.cpp

@@ -50,6 +50,13 @@ static inline void cpuid(int index, int *data)
 {
 #if _MSC_VER
     __cpuid(data, index);
+#elif OCIO_ARCH_X86_32
+    __asm__ volatile (
+        "mov    %%ebx, %%esi \n\t"
+        "cpuid               \n\t"
+        "xchg   %%ebx, %%esi"
+        : "=a" (data[0]), "=S" (data[1]), "=c" (data[2]), "=d" (data[3])
+        : "0" (index), "2"(0));
 #else
     __asm__ volatile (
         "mov    %%rbx, %%rsi \n\t"

src/OpenColorIO/CPUInfoConfig.h.in

@@ -3,6 +3,7 @@
 
 
 #cmakedefine01 OCIO_ARCH_X86
+#cmakedefine01 OCIO_ARCH_X86_32
 
 // Relevant only for arm64 architecture.
 #if defined(__aarch64__)