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# HG changeset patch
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# User Lars T Hansen <lhansen@mozilla.com>
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# Date 1519822672 -3600
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# Node ID 800abe66894d6b07b24bccecbf6a65e2261076f6
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# Parent 223c97459e96183eb616aed39147207bdb953ba8
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Bug 1375074 - Save and restore non-volatile x28 on ARM64 for generated unboxed object constructor. r=sstangl
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Origin: upstream
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Applied-upstream: 61, commit: https://hg.mozilla.org/mozilla-central/rev/800abe66894d
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---
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js/src/vm/UnboxedObject.cpp | 30 ++++++++++++++++++++++++++----
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1 file changed, 26 insertions(+), 4 deletions(-)
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diff --git a/js/src/vm/UnboxedObject.cpp b/js/src/vm/UnboxedObject.cpp
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index 35ca20d7405f..1c20a1093d13 100644
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--- a/js/src/vm/UnboxedObject.cpp
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+++ b/js/src/vm/UnboxedObject.cpp
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@@ -86,9 +86,16 @@ static const uintptr_t CLEAR_CONSTRUCTOR_CODE_TOKEN = 0x1;
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#endif
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#ifdef JS_CODEGEN_ARM64
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- // ARM64 communicates stack address via sp, but uses a pseudo-sp for
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- // addressing.
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- masm.initStackPtr();
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+ // ARM64 communicates stack address via sp, but uses a pseudo-sp (PSP) for
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+ // addressing. The register we use for PSP may however also be used by
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+ // calling code, and it is nonvolatile, so save it. Do this as a special
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+ // case first because the generic save/restore code needs the PSP to be
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+ // initialized already.
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+ MOZ_ASSERT(PseudoStackPointer64.Is(masm.GetStackPointer64()));
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+ masm.Str(PseudoStackPointer64, vixl::MemOperand(sp, -16, vixl::PreIndex));
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+
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+ // Initialize the PSP from the SP.
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+ masm.initStackPtr();
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#endif
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MOZ_ASSERT(propertiesReg.volatile_());
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@@ -239,7 +246,22 @@ static const uintptr_t CLEAR_CONSTRUCTOR_CODE_TOKEN = 0x1;
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if (ScratchDoubleReg.volatile_()) masm.pop(ScratchDoubleReg);
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masm.PopRegsInMask(savedNonVolatileRegisters);
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- masm.abiret();
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+#ifdef JS_CODEGEN_ARM64
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+ // Now restore the value that was in the PSP register on entry, and return.
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+
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+ // Obtain the correct SP from the PSP.
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+ masm.Mov(sp, PseudoStackPointer64);
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+
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+ // Restore the saved value of the PSP register, this value is whatever the
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+ // caller had saved in it, not any actual SP value, and it must not be
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+ // overwritten subsequently.
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+ masm.Ldr(PseudoStackPointer64, vixl::MemOperand(sp, 16, vixl::PostIndex));
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+
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+ // Perform a plain Ret(), as abiret() will move SP <- PSP and that is wrong.
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+ masm.Ret(vixl::lr);
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+#else
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+ masm.abiret();
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+#endif
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masm.bind(&failureStoreOther);
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--
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2.21.0
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