Merge pull request #74014 from Azoy/60-fix-invertible-abi

[6.0] [IRGen] Fix misalignment of conditional invertible requirement counts

Author: Azoy

include/swift/ABI/GenericContext.h

@@ -23,6 +23,7 @@
 #include "swift/ABI/MetadataRef.h"
 #include "swift/ABI/InvertibleProtocols.h"
 #include "swift/ABI/TrailingObjects.h"
+#include "swift/Basic/MathUtils.h"
 #include "swift/Demangling/Demangle.h"
 
 namespace swift {
@@ -696,7 +697,7 @@ class TrailingGenericContextObjects<TargetSelf<Runtime>,
     if (!asSelf()->hasConditionalInvertedProtocols())
       return 0;
 
-    return countBitsUsed(getConditionalInvertedProtocols().rawBits());
+    return popcount(getConditionalInvertedProtocols().rawBits());
   }
 
   size_t numTrailingObjects(

include/swift/Basic/MathUtils.h

@@ -17,7 +17,13 @@
 #ifndef SWIFT_BASIC_MATH_UTILS_H
 #define SWIFT_BASIC_MATH_UTILS_H
 
+#include "Compiler.h"
 #include <cstddef>
+#include <cstdint>
+
+#if SWIFT_COMPILER_IS_MSVC
+#include <intrin.h>
+#endif
 
 namespace swift {
 
@@ -33,6 +39,21 @@ static inline size_t roundUpToAlignMask(size_t size, size_t alignMask) {
   return (size + alignMask) & ~alignMask;
 }
 
+static inline unsigned popcount(unsigned value) {
+#if SWIFT_COMPILER_IS_MSVC && (defined(_M_IX86) || defined(_M_X64))
+  // The __popcnt intrinsic is only available when targetting x86{_64} with MSVC.
+  return __popcnt(value);
+#elif __has_builtin(__builtin_popcount)
+  return __builtin_popcount(value);
+#else
+  // From llvm/ADT/bit.h which the runtime doesn't have access to (yet?)
+  uint32_t v = value;
+  v = v - ((v >> 1) & 0x55555555);
+  v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
+  return int(((v + (v >> 4) & 0xF0F0F0F) * 0x1010101) >> 24);
+#endif
+}
+
 } // namespace swift
 
 #endif // #ifndef SWIFT_BASIC_MATH_UTILS_H

lib/IRGen/GenMeta.cpp

@@ -1334,6 +1334,13 @@ namespace {
             B.addPlaceholderWithSize(IGM.Int16Ty));
       }
 
+      // The conditional invertible protocol set is alone as a 16 bit slot, so
+      // an even amount of conditional invertible protocols will cause an uneven
+      // alignment.
+      if ((numProtocols & 1) == 0) {
+        B.addInt16(0);
+      }
+
       // Emit the generic requirements for the conditional conformance
       // to each invertible protocol.
       auto nominal = cast<NominalTypeDecl>(Type);