Re: [swift-dev] Builtin.loadRaw

[Sam Ding via swift-dev]

Hi Slava & Joe,

Thank you for the response.

The failed test case is "generic instantiation" of KeyPath.swift. Here is
details of log:
      [ RUN      ] key paths.key path generic instantiation
      stdout>>> check failed
      at /home/wk/sw4/swift/test/stdlib/KeyPath.swift, line 193
      stdout>>> expected: Swift.ReferenceWritableKeyPath<a.S<Swift.Int>,
      Swift.Int> (of type Swift.ReferenceWritableKeyPath<a.S<Swift.Int>,
      Swift.Int>)
      stdout>>> actual: Swift.ReferenceWritableKeyPath<a.S<Swift.Int>,
      Swift.Int> (of type Swift.ReferenceWritableKeyPath<a.S<Swift.Int>,
      Swift.Int>)
      stdout>>> check failed
      at /home/wk/sw4/swift/test/stdlib/KeyPath.swift, line 197
      stdout>>> expected: Swift.ReferenceWritableKeyPath<a.S<Swift.String>,
      Swift.Int> (of type Swift.ReferenceWritableKeyPath<a.S<Swift.String>,
      Swift.Int>)
      stdout>>> actual: Swift.ReferenceWritableKeyPath<a.S<Swift.String>,
      Swift.Int> (of type Swift.ReferenceWritableKeyPath<a.S<Swift.String>,
      Swift.Int>)
      stdout>>> check failed
      at /home/wk/sw4/swift/test/stdlib/KeyPath.swift, line 201
      stdout>>> expected:
      Swift.ReferenceWritableKeyPath<a.S<StdlibUnittest.LifetimeTracked>,
      Swift.Int> (of type
      Swift.ReferenceWritableKeyPath<a.S<StdlibUnittest.LifetimeTracked>,
      Swift.Int>)
      stdout>>> actual:
      Swift.ReferenceWritableKeyPath<a.S<StdlibUnittest.LifetimeTracked>,
      Swift.Int> (of type
      Swift.ReferenceWritableKeyPath<a.S<StdlibUnittest.LifetimeTracked>,
      Swift.Int>)
      [     FAIL ] key paths.key path generic instantiation

Other test cases of KeyPath.siwft are all passed.
It is found that the failure reason is @stdlib/public/core/KeyPath.swift

        85           if aComponent.header.endOfReferencePrefix
        86               != bComponent.header.endOfReferencePrefix
        87             || aComponent.value != bComponent.value     // this
      is true on s390x,  aComponent.value="struct(0)",
      bComponent.value="struct(48)"
        88             || aType != bType {
        89             return false
        90           }

Then tracing to:

   2094     func tryToResolveOffset() {
   2095       if header.payload ==
   RawKeyPathComponent.Header.unresolvedFieldOffsetPayload {
   2096         // Look up offset in type metadata. The value in the
   pattern is the
   2097         // offset within the metadata object.
   2098         let metadataPtr = unsafeBitCast(base, to:
   UnsafeRawPointer.self)
   2099         let offsetOfOffset = patternBuffer.pop(UInt32.self)
   2100 print("+++++++++++ int_offsetOfOffset=\(Int(offsetOfOffset))\n")
   2101         var offset = metadataPtr.load(fromByteOffset: Int
   (offsetOfOffset),     // given the same input parameters
   (offsetOfOfferset=56),
   2102                                       as:
   UInt32.self)                                           //  different
   "offset" (0 on s390x, and 48 on  x86_64)
   2103         // Rewrite the header for a resolved offset.


Then it comes Builtin.loadRaw of UnsafeRawPointer.swift.gyb

As My lldb and gdb do not stop @ emitBuiltinLoadRaw(),
I inserted a "printf" in the fucntion, but it does not print out anything.

Yes,  I think it maybe related to alignment or endianness, so we need to
find the source code of LoadRaw.


Thanks,


Sam Ding,
Linux on z Systems  Open Source Ecosystem
IBM Toronto Lab,
email: samd...@ca.ibm.com
phone: (905)413-2947



From:   Slava Pestov <spes...@apple.com>
To:     Sam Ding <samd...@ca.ibm.com>
Cc:     swift-dev <swift-dev@swift.org>
Date:   09/28/2017 05:24 PM
Subject:        Re: [swift-dev] Builtin.loadRaw
Sent by:        spes...@apple.com



Hi Sam,

The builtin is defined in lib/SILGen/SILGenBuiltin.cpp, look for the
function named emitBuiltinLoadRaw().

However I suspect the problem in this case is not that the builtin is
implemented incorrectly (it eventually lowers to an LLVM load instruction)
but that something further upstream is going wrong, perhaps with alignment
or endianness.

Can you tell us which unit tests are failing specifically?

Slava

      On Sep 28, 2017, at 2:16 PM, Sam Ding via swift-dev <
      swift-dev@swift.org> wrote:



      I am testing a test case "KeyPath.swift" on s390x for v4.0 . It is
      found that " Builtin.loadRaw" as the below of
      "stdlib/public/core/UnsafeRawPointer.swift.gyb" returns a different
      value than that on x86-64.


            @_inlineable
            public func load<T>(fromByteOffset offset: Int = 0, as type:
            T.Type) -> T {
            _debugPrecondition(0 == (UInt(bitPattern: self + offset)
            & (UInt(MemoryLayout<T>.alignment) - 1)),
            "load from misaligned raw pointer")

            return Builtin.loadRaw((self + offset)._rawValue) // return a
            different value on s390x vs x86-64
            }
      My debugger (lldb) does not guide me to the detailed of "
      Builtin.loadRaw". Searching "loadRaw" and finding
            swift/include/swift/AST/Builtins.def:BUILTIN_SIL_OPERATION
            (LoadRaw, "loadRaw", Special)

      But I could not find the definition of this "LoadRaw" from the whole
      swift v4.
      Can anyone give me a hint where its implementation is?

      Thanks,


      Sam Ding,
      Linux on z Systems Open Source Ecosystem
      IBM Toronto Lab,
      email: samd...@ca.ibm.com
      phone: (905)413-2947
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