1 

     2 # HG changeset patch

     3 # User Lars T Hansen <lhansen@mozilla.com>

     4 # Date 1519822672 -3600

     5 # Node ID 800abe66894d6b07b24bccecbf6a65e2261076f6

     6 # Parent  223c97459e96183eb616aed39147207bdb953ba8

     7 Bug 1375074 - Save and restore non-volatile x28 on ARM64 for generated unboxed object constructor.  r=sstangl

     8 

     9 diff --git a/js/src/jit-test/tests/bug1375074.js b/js/src/jit-test/tests/bug1375074.js

    10 new file mode 100644

    11 --- /dev/null

    12 +++ b/js/src/jit-test/tests/bug1375074.js

    13 @@ -0,0 +1,18 @@

    14 +// This forces the VM to start creating unboxed objects and thus stresses a

    15 +// particular path into generated code for a specialized unboxed object

    16 +// constructor.

    17 +

    18 +var K = 2000;			// 2000 should be plenty

    19 +var s = "[";

    20 +var i;

    21 +for ( i=0; i < K-1; i++ )

    22 +    s = s + `{"i":${i}},`;

    23 +s += `{"i":${i}}]`;

    24 +var v = JSON.parse(s);

    25 +

    26 +assertEq(v.length == K, true);

    27 +

    28 +for ( i=0; i < K; i++) {

    29 +    assertEq(v[i] instanceof Object, true);

    30 +    assertEq(v[i].i, i);

    31 +}

    32 diff --git a/js/src/vm/UnboxedObject.cpp b/js/src/vm/UnboxedObject.cpp

    33 --- a/js/src/vm/UnboxedObject.cpp

    34 +++ b/js/src/vm/UnboxedObject.cpp

    35 @@ -90,17 +90,25 @@ UnboxedLayout::makeConstructorCode(JSCon

    36      masm.loadPtr(Address(masm.getStackPointer(), sizeof(void*)), propertiesReg);

    37      masm.loadPtr(Address(masm.getStackPointer(), 2 * sizeof(void*)), newKindReg);

    38  #else

    39      propertiesReg = IntArgReg0;

    40      newKindReg = IntArgReg1;

    41  #endif

    42  

    43  #ifdef JS_CODEGEN_ARM64

    44 -    // ARM64 communicates stack address via sp, but uses a pseudo-sp for addressing.

    45 +    // ARM64 communicates stack address via sp, but uses a pseudo-sp (PSP) for

    46 +    // addressing.  The register we use for PSP may however also be used by

    47 +    // calling code, and it is nonvolatile, so save it.  Do this as a special

    48 +    // case first because the generic save/restore code needs the PSP to be

    49 +    // initialized already.

    50 +    MOZ_ASSERT(PseudoStackPointer64.Is(masm.GetStackPointer64()));

    51 +    masm.Str(PseudoStackPointer64, vixl::MemOperand(sp, -16, vixl::PreIndex));

    52 +

    53 +    // Initialize the PSP from the SP.

    54      masm.initStackPtr();

    55  #endif

    56  

    57      MOZ_ASSERT(propertiesReg.volatile_());

    58      MOZ_ASSERT(newKindReg.volatile_());

    59  

    60      AllocatableGeneralRegisterSet regs(GeneralRegisterSet::All());

    61      regs.take(propertiesReg);

    62 @@ -228,17 +236,32 @@ UnboxedLayout::makeConstructorCode(JSCon

    63      if (object != ReturnReg)

    64          masm.movePtr(object, ReturnReg);

    65  

    66      // Restore non-volatile registers which were saved on entry.

    67      if (ScratchDoubleReg.volatile_())

    68          masm.pop(ScratchDoubleReg);

    69      masm.PopRegsInMask(savedNonVolatileRegisters);

    70  

    71 +#ifdef JS_CODEGEN_ARM64

    72 +    // Now restore the value that was in the PSP register on entry, and return.

    73 +

    74 +    // Obtain the correct SP from the PSP.

    75 +    masm.Mov(sp, PseudoStackPointer64);

    76 +

    77 +    // Restore the saved value of the PSP register, this value is whatever the

    78 +    // caller had saved in it, not any actual SP value, and it must not be

    79 +    // overwritten subsequently.

    80 +    masm.Ldr(PseudoStackPointer64, vixl::MemOperand(sp, 16, vixl::PostIndex));

    81 +

    82 +    // Perform a plain Ret(), as abiret() will move SP <- PSP and that is wrong.

    83 +    masm.Ret(vixl::lr);

    84 +#else

    85      masm.abiret();

    86 +#endif

    87  

    88      masm.bind(&failureStoreOther);

    89  

    90      // There was a failure while storing a value which cannot be stored at all

    91      // in the unboxed object. Initialize the object so it is safe for GC and

    92      // return null.

    93      masm.initUnboxedObjectContents(object, templateObject);

    94  

    95