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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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# Wed Feb 28 13:57:52 2018 +0100
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# Node ID 672f0415217b202ae59a930769dffd9d6ba6b87c
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# Parent 825fd04dacc6297d3a980ec4184079405950b35d
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Bug 1375074 - Save and restore non-volatile x28 on ARM64 for generated unboxed object constructor.
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diff --git a/js/src/jit-test/tests/bug1375074.js b/js/src/jit-test/tests/bug1375074.js
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new file mode 100644
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--- /dev/null
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+++ b/js/src/jit-test/tests/bug1375074.js
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@@ -0,0 +1,18 @@
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+// This forces the VM to start creating unboxed objects and thus stresses a
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+// particular path into generated code for a specialized unboxed object
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+// constructor.
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+
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+var K = 2000; // 2000 should be plenty
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+var s = "[";
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+var i;
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+for ( i=0; i < K-1; i++ )
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+ s = s + `{"i":${i}},`;
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+s += `{"i":${i}}]`;
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+var v = JSON.parse(s);
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+
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+assertEq(v.length == K, true);
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+
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+for ( i=0; i < K; i++) {
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+ assertEq(v[i] instanceof Object, true);
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+ assertEq(v[i].i, i);
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+}
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diff --git a/js/src/vm/UnboxedObject.cpp b/js/src/vm/UnboxedObject.cpp
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--- a/js/src/vm/UnboxedObject.cpp
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+++ b/js/src/vm/UnboxedObject.cpp
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@@ -95,7 +95,15 @@ UnboxedLayout::makeConstructorCode(JSCon
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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 addressing.
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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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@@ -233,7 +241,22 @@ UnboxedLayout::makeConstructorCode(JSCon
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masm.pop(ScratchDoubleReg);
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masm.PopRegsInMask(savedNonVolatileRegisters);
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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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