Allow building x86 and arm on msvc (#1147)

Summary:
A couple of changes to support building folly in MSVC/win32 for x86 and arm platforms.
Pull Request resolved: https://github.com/facebook/folly/pull/1147

Reviewed By: Orvid

Differential Revision: D15592309

Pulled By: yfeldblum

fbshipit-source-id: 97860ab9309e5492bfadac56079af735741d4a2c

folly/memory/detail/MallocImpl.h

@@ -50,6 +50,19 @@ extern int (
 #ifdef _MSC_VER
 // We emulate weak linkage for MSVC. The symbols we're
 // aliasing to are hiding in MallocImpl.cpp
+#if defined(_M_IX86)
+#pragma comment(linker, "/alternatename:_mallocx=_mallocxWeak")
+#pragma comment(linker, "/alternatename:_rallocx=_rallocxWeak")
+#pragma comment(linker, "/alternatename:_xallocx=_xallocxWeak")
+#pragma comment(linker, "/alternatename:_sallocx=_sallocxWeak")
+#pragma comment(linker, "/alternatename:_dallocx=_dallocxWeak")
+#pragma comment(linker, "/alternatename:_sdallocx=_sdallocxWeak")
+#pragma comment(linker, "/alternatename:_nallocx=_nallocxWeak")
+#pragma comment(linker, "/alternatename:_mallctl=_mallctlWeak")
+#pragma comment( \
+    linker, "/alternatename:_mallctlnametomib=_mallctlnametomibWeak")
+#pragma comment(linker, "/alternatename:_mallctlbymib=_mallctlbymibWeak")
+#else
 #pragma comment(linker, "/alternatename:mallocx=mallocxWeak")
 #pragma comment(linker, "/alternatename:rallocx=rallocxWeak")
 #pragma comment(linker, "/alternatename:xallocx=xallocxWeak")
@@ -62,4 +75,5 @@ extern int (
 #pragma comment(linker, "/alternatename:mallctlbymib=mallctlbymibWeak")
 #endif
 #endif
+#endif
 }

folly/portability/Builtins.h

@@ -50,10 +50,21 @@ FOLLY_ALWAYS_INLINE int __builtin_clzl(unsigned long x) {
   return __builtin_clz((unsigned int)x);
 }
 
+#if defined(_M_IX86) || defined(_M_ARM)
+FOLLY_ALWAYS_INLINE int __builtin_clzll(unsigned long long x) {
+  if (x == 0) {
+    return 64;
+  }
+  unsigned int msb = (unsigned int)(x >> 32);
+  unsigned int lsb = (unsigned int)x;
+  return (msb != 0) ? __builtin_clz(msb) : 32 + __builtin_clz(lsb);
+}
+#else
 FOLLY_ALWAYS_INLINE int __builtin_clzll(unsigned long long x) {
   unsigned long index;
   return int(_BitScanReverse64(&index, x) ? 63 - index : 64);
 }
+#endif
 
 FOLLY_ALWAYS_INLINE int __builtin_ctz(unsigned int x) {
   unsigned long index;
@@ -64,10 +75,23 @@ FOLLY_ALWAYS_INLINE int __builtin_ctzl(unsigned long x) {
   return __builtin_ctz((unsigned int)x);
 }
 
+#if defined(_M_IX86) || defined(_M_ARM)
+FOLLY_ALWAYS_INLINE int __builtin_ctzll(unsigned long long x) {
+  unsigned long index;
+  unsigned int msb = (unsigned int)(x >> 32);
+  unsigned int lsb = (unsigned int)x;
+  if (lsb != 0) {
+    return (int)(_BitScanForward(&index, lsb) ? index : 64);
+  } else {
+    return (int)(_BitScanForward(&index, msb) ? index + 32 : 64);
+  }
+}
+#else
 FOLLY_ALWAYS_INLINE int __builtin_ctzll(unsigned long long x) {
   unsigned long index;
   return int(_BitScanForward64(&index, x) ? index : 64);
 }
+#endif
 
 FOLLY_ALWAYS_INLINE int __builtin_ffs(int x) {
   unsigned long index;
@@ -78,6 +102,12 @@ FOLLY_ALWAYS_INLINE int __builtin_ffsl(long x) {
   return __builtin_ffs(int(x));
 }
 
+#if defined(_M_IX86) || defined(_M_ARM)
+FOLLY_ALWAYS_INLINE int __builtin_ffsll(long long x) {
+  int ctzll = __builtin_ctzll((unsigned long long)x);
+  return ctzll != 64 ? ctzll + 1 : 0;
+}
+#else
 FOLLY_ALWAYS_INLINE int __builtin_ffsll(long long x) {
   unsigned long index;
   return int(_BitScanForward64(&index, (unsigned long long)x) ? index + 1 : 0);
@@ -91,10 +121,18 @@ FOLLY_ALWAYS_INLINE int __builtin_popcountl(unsigned long x) {
   static_assert(sizeof(x) == 4, "");
   return int(__popcnt(x));
 }
+#endif
 
+#if defined(_M_IX86)
+FOLLY_ALWAYS_INLINE int __builtin_popcountll(unsigned long long x) {
+  return int(__popcnt((unsigned int)(x >> 32))) +
+      int(__popcnt((unsigned int)x));
+}
+#elif defined(_M_X64)
 FOLLY_ALWAYS_INLINE int __builtin_popcountll(unsigned long long x) {
   return int(__popcnt64(x));
 }
+#endif
 
 FOLLY_ALWAYS_INLINE void* __builtin_return_address(unsigned int frame) {
   // I really hope frame is zero...