commit cf80106b1322de3c43ac1c0c8605b4a0db6f0b8d
author Matthew G McGovern <matthew.mcgovern@microsoft.com> Thu Aug 22 20:44:34 2019 +0000
committer Matthew G McGovern <matthew.mcgovern@microsoft.com> Thu Aug 22 20:44:34 2019 +0000
tree 41909db8f6f53187aa137a15cfd90fd9a4d6af7e
parent 784073907c0695388e672350a7741c35bdd23034

LibFuzzer support for 32bit MSVC

This fixes the two build errors when trying to compile LibFuzzer for
32bit with MSVC.

    - authored by Max Shavrick (mxms at microsoft)

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@369704 91177308-0d34-0410-b5e6-96231b3b80d8

lib/fuzzer/FuzzerBuiltinsMsvc.h

diff --git a/lib/fuzzer/FuzzerBuiltinsMsvc.h b/lib/fuzzer/FuzzerBuiltinsMsvc.h
index 82709cf..bc65c60 100644
--- a/lib/fuzzer/FuzzerBuiltinsMsvc.h
+++ b/lib/fuzzer/FuzzerBuiltinsMsvc.h
@@ -15,9 +15,6 @@
 #include "FuzzerDefs.h"
 
 #if LIBFUZZER_MSVC
-#if !defined(_M_ARM) && !defined(_M_X64)
-#error "_BitScanReverse64 unavailable on this platform so MSVC is unsupported."
-#endif
 #include <intrin.h>
 #include <cstdint>
 #include <cstdlib>
@@ -40,7 +37,18 @@
 // outside of Windows.
 inline uint32_t Clzll(uint64_t X) {
   unsigned long LeadZeroIdx = 0;
+
+#if !defined(_M_ARM) && !defined(_M_X64)
+  // Scan the high 32 bits.
+  if (_BitScanReverse(&LeadZeroIdx, static_cast<unsigned long>(X >> 32)))
+    return static_cast<int>(63 - (LeadZeroIdx + 32)); // Create a bit offset from the MSB.
+  // Scan the low 32 bits.
+  if (_BitScanReverse(&LeadZeroIdx, static_cast<unsigned long>(X)))
+    return static_cast<int>(63 - LeadZeroIdx);
+
+#else
   if (_BitScanReverse64(&LeadZeroIdx, X)) return 63 - LeadZeroIdx;
+#endif
   return 64;
 }
 
@@ -50,7 +58,13 @@
   return 32;
 }
 
-inline int Popcountll(unsigned long long X) { return __popcnt64(X); }
+inline int Popcountll(unsigned long long X) {
+#if !defined(_M_ARM) && !defined(_M_X64)
+  return __popcnt(X) + __popcnt(X >> 32);
+#else
+  return __popcnt64(X);
+#endif
+}
 
 }  // namespace fuzzer