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# HG changeset patch
# User Lars T Hansen <lhansen@mozilla.com>
# Date 1519822672 -3600
# Wed Feb 28 13:57:52 2018 +0100
# Node ID 672f0415217b202ae59a930769dffd9d6ba6b87c
# Parent 825fd04dacc6297d3a980ec4184079405950b35d
Bug 1375074 - Save and restore non-volatile x28 on ARM64 for generated unboxed object constructor.
diff --git a/js/src/jit-test/tests/bug1375074.js b/js/src/jit-test/tests/bug1375074.js
new file mode 100644
--- /dev/null
+++ b/js/src/jit-test/tests/bug1375074.js
@@ -0,0 +1,18 @@
+// This forces the VM to start creating unboxed objects and thus stresses a
+// particular path into generated code for a specialized unboxed object
+// constructor.
+
+var K = 2000; // 2000 should be plenty
+var s = "[";
+var i;
+for ( i=0; i < K-1; i++ )
+ s = s + `{"i":${i}},`;
+s += `{"i":${i}}]`;
+var v = JSON.parse(s);
+
+assertEq(v.length == K, true);
+
+for ( i=0; i < K; i++) {
+ assertEq(v[i] instanceof Object, true);
+ assertEq(v[i].i, i);
+}
diff --git a/js/src/vm/UnboxedObject.cpp b/js/src/vm/UnboxedObject.cpp
--- a/js/src/vm/UnboxedObject.cpp
+++ b/js/src/vm/UnboxedObject.cpp
@@ -95,7 +95,15 @@ UnboxedLayout::makeConstructorCode(JSCon
#endif
#ifdef JS_CODEGEN_ARM64
- // ARM64 communicates stack address via sp, but uses a pseudo-sp for addressing.
+ // ARM64 communicates stack address via sp, but uses a pseudo-sp (PSP) for
+ // addressing. The register we use for PSP may however also be used by
+ // calling code, and it is nonvolatile, so save it. Do this as a special
+ // case first because the generic save/restore code needs the PSP to be
+ // initialized already.
+ MOZ_ASSERT(PseudoStackPointer64.Is(masm.GetStackPointer64()));
+ masm.Str(PseudoStackPointer64, vixl::MemOperand(sp, -16, vixl::PreIndex));
+
+ // Initialize the PSP from the SP.
masm.initStackPtr();
#endif
@@ -233,7 +241,22 @@ UnboxedLayout::makeConstructorCode(JSCon
masm.pop(ScratchDoubleReg);
masm.PopRegsInMask(savedNonVolatileRegisters);
+#ifdef JS_CODEGEN_ARM64
+ // Now restore the value that was in the PSP register on entry, and return.
+
+ // Obtain the correct SP from the PSP.
+ masm.Mov(sp, PseudoStackPointer64);
+
+ // Restore the saved value of the PSP register, this value is whatever the
+ // caller had saved in it, not any actual SP value, and it must not be
+ // overwritten subsequently.
+ masm.Ldr(PseudoStackPointer64, vixl::MemOperand(sp, 16, vixl::PostIndex));
+
+ // Perform a plain Ret(), as abiret() will move SP <- PSP and that is wrong.
+ masm.Ret(vixl::lr);
+#else
masm.abiret();
+#endif
masm.bind(&failureStoreOther);
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