Towards s390x support (#19822)

* Towards s390x support

* Fix case index on Big Endian

Author: rposts

stdlib/public/SwiftShims/HeapObject.h

@@ -171,9 +171,9 @@ static_assert(alignof(HeapObject) == alignof(void*),
 #define _swift_abi_SwiftSpareBitsMask                                          \
   (__swift_uintptr_t) SWIFT_ABI_S390X_SWIFT_SPARE_BITS_MASK
 #define _swift_abi_ObjCReservedBitsMask                                        \
-  (__swift_uintptr_t) SWIFT_ABI_DEFAULT_OBJC_RESERVED_BITS_MASK
+  (__swift_uintptr_t) SWIFT_ABI_S390X_OBJC_RESERVED_BITS_MASK
 #define _swift_abi_ObjCReservedLowBits                                         \
-  (unsigned) SWIFT_ABI_DEFAULT_OBJC_NUM_RESERVED_LOW_BITS
+  (unsigned) SWIFT_ABI_S390X_OBJC_NUM_RESERVED_LOW_BITS
 #define _swift_BridgeObject_TaggedPointerBits                                  \
   (__swift_uintptr_t) SWIFT_ABI_DEFAULT_BRIDGEOBJECT_TAG_64
 

stdlib/public/SwiftShims/System.h

@@ -164,6 +164,24 @@
 /*********************************** s390x ************************************/
 
 // Top byte of pointers is unused, and heap objects are eight-byte aligned.
-#define SWIFT_ABI_S390X_SWIFT_SPARE_BITS_MASK 0x0000000000000007ULL
+// On s390x it is theoretically possible to have high bit set but in practice
+// it is unlikely.
+#define SWIFT_ABI_S390X_SWIFT_SPARE_BITS_MASK 0xFF00000000000007ULL
+
+// Objective-C reserves just the high bit for tagged pointers.
+#define SWIFT_ABI_S390X_OBJC_RESERVED_BITS_MASK 0x8000000000000000ULL
+#define SWIFT_ABI_S390X_OBJC_NUM_RESERVED_LOW_BITS 0
+
+// BridgeObject uses this bit to indicate whether it holds an ObjC object or
+// not.
+#define SWIFT_ABI_S390X_IS_OBJC_BIT 0x4000000000000000ULL
+
+// ObjC weak reference discriminator is the high bit
+// reserved for ObjC tagged pointers plus the LSB.
+#define SWIFT_ABI_S390X_OBJC_WEAK_REFERENCE_MARKER_MASK  \
+  (SWIFT_ABI_S390X_OBJC_RESERVED_BITS_MASK |          \
+   1<<SWIFT_ABI_S390X_OBJC_NUM_RESERVED_LOW_BITS)
+#define SWIFT_ABI_S390X_OBJC_WEAK_REFERENCE_MARKER_VALUE \
+  (1<<SWIFT_ABI_S390X_OBJC_NUM_RESERVED_LOW_BITS)
 
 #endif /* SWIFT_ABI_SYSTEM_H */

stdlib/public/core/CTypes.swift

@@ -82,6 +82,11 @@ public typealias CLongDouble = Double
 public typealias CLongDouble = Float80
 #endif
 // TODO: Fill in definitions for other OSes.
+#if arch(s390x)
+// On s390x '-mlong-double-64' option with size of 64-bits makes the
+// Long Double type equivalent to Double type.
+public typealias CLongDouble = Double
+#endif
 #endif
 
 // FIXME: Is it actually UTF-32 on Darwin?

stdlib/public/runtime/EnumImpl.h

@@ -110,16 +110,19 @@ inline unsigned getEnumTagSinglePayloadImpl(
       unsigned caseIndexFromExtraTagBits =
           payloadSize >= 4 ? 0 : (extraTagBits - 1U) << (payloadSize * 8U);
 
+#if defined(__BIG_ENDIAN__)
+      // On BE high order bytes contain the index
+      unsigned long caseIndexFromValue = 0;
+      unsigned numPayloadTagBytes = std::min(size_t(8), payloadSize);
+      if (numPayloadTagBytes)
+        memcpy(reinterpret_cast<uint8_t *>(&caseIndexFromValue) + 8 -
+               numPayloadTagBytes,
+               valueAddr, numPayloadTagBytes);
+#else
       // In practice we should need no more than four bytes from the payload
       // area.
       unsigned caseIndexFromValue = 0;
       unsigned numPayloadTagBytes = std::min(size_t(4), payloadSize);
-#if defined(__BIG_ENDIAN__)
-      if (numPayloadTagBytes)
-        small_memcpy(reinterpret_cast<uint8_t *>(&caseIndexFromValue) + 4 -
-                         numPayloadTagBytes,
-                     valueAddr, numPayloadTagBytes, true);
-#else
       if (numPayloadTagBytes)
         small_memcpy(&caseIndexFromValue, valueAddr,
                      numPayloadTagBytes, true);
@@ -192,6 +195,8 @@ inline void storeEnumTagSinglePayloadImpl(
                  reinterpret_cast<uint8_t *>(&payloadIndex) + 4 -
                      numPayloadTagBytes,
                  numPayloadTagBytes, true);
+  if (payloadSize > 4)
+	    memset(valueAddr + 4, 0, payloadSize - 4);
   if (numExtraTagBytes)
     small_memcpy(extraTagBitAddr,
                  reinterpret_cast<uint8_t *>(&extraTagIndex) + 4 -

stdlib/public/runtime/HeapObject.cpp

@@ -61,9 +61,11 @@ using namespace swift;
 /// Returns true if the pointer passed to a native retain or release is valid.
 /// If false, the operation should immediately return.
 static inline bool isValidPointerForNativeRetain(const void *p) {
-#if defined(__x86_64__) || defined(__arm64__) || defined(__aarch64__) || defined(_M_ARM64)
-  // On these platforms, the upper half of address space is reserved for the
+#if defined(__x86_64__) || defined(__arm64__) || defined(__aarch64__) || defined(_M_ARM64) || defined(__s390x__)
+  // On these platforms, except s390x, the upper half of address space is reserved for the
   // kernel, so we can assume that pointer values in this range are invalid.
+  // On s390x it is theoretically possible to have high bit set but in practice
+  // it is unlikely.
   return (intptr_t)p > 0;
 #else
   return p != nullptr;