# 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);