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Future-proof the ARM64 ABI by not reserving the entire top byte. #21015

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Merged
merged 1 commit into from
Dec 5, 2018
Merged

Future-proof the ARM64 ABI by not reserving the entire top byte. #21015

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5 changes: 3 additions & 2 deletions stdlib/public/SwiftShims/System.h
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Original file line number Diff line number Diff line change
Expand Up @@ -136,9 +136,10 @@
/// Darwin reserves the low 4GB of address space.
#define SWIFT_ABI_DARWIN_ARM64_LEAST_VALID_POINTER 0x100000000ULL

// TBI guarantees the top byte of pointers is unused.
// TBI guarantees the top byte of pointers is unused, but ARMv8.5-A
// claims the bottom four bits of that for memory tagging.
// Heap objects are eight-byte aligned.
#define SWIFT_ABI_ARM64_SWIFT_SPARE_BITS_MASK 0xFF00000000000007ULL
#define SWIFT_ABI_ARM64_SWIFT_SPARE_BITS_MASK 0xF000000000000007ULL

// Objective-C reserves just the high bit for tagged pointers.
#define SWIFT_ABI_ARM64_OBJC_RESERVED_BITS_MASK 0x8000000000000000ULL
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4 changes: 2 additions & 2 deletions test/IRGen/bridge_object_arm64.sil
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Expand Up @@ -35,8 +35,8 @@ entry(%c : $C, %w : $Builtin.Word):
// CHECK: [[TAGGED_RESULT:%.*]] = bitcast [[BRIDGE]] %0 to [[C:%objc_object\*]]
// CHECK: br label %tagged-cont
// CHECK: not-tagged-pointer:
// -- 0x00ff_ffff_ffff_fff8
// CHECK: [[MASKED_BITS:%.*]] = and i64 [[BOBITS]], 72057594037927928
// -- 0x0fff_ffff_ffff_fff8
// CHECK: [[MASKED_BITS:%.*]] = and i64 [[BOBITS]], 1152921504606846968
// CHECK: [[MASKED_RESULT:%.*]] = inttoptr i64 [[MASKED_BITS]] to [[C]]
// CHECK: br label %tagged-cont
// CHECK: tagged-cont:
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