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Bug 1116855 - Tolerate any input register when storing bytes on x86, r=jandem.

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This commit is contained in:
Brian Hackett 2015-02-01 07:43:02 -07:00
parent 23f3f9f4fa
commit 51def7fb13
1 changed files with 45 additions and 2 deletions
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47
js/src/jit/shared/MacroAssembler-x86-shared.h
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@ -650,6 +650,44 @@ class MacroAssemblerX86Shared : public Assembler
Condition cond = testDoubleTruthy(truthy, reg);
j(cond, label);
}
// Class which ensures that registers used in byte ops are compatible with
// such instructions, even if the original register passed in wasn't. This
// only applies to x86, as on x64 all registers are valid single byte regs.
// This doesn't lead to great code but helps to simplify code generation.
class AutoEnsureByteRegister {
MacroAssemblerX86Shared *masm;
Register reg_;
bool read_;
public:
template <typename T>
AutoEnsureByteRegister(MacroAssemblerX86Shared *masm, T address, Register reg, bool read)
: masm(masm), reg_(reg), read_(read)
{
if (!GeneralRegisterSet(Registers::SingleByteRegs).has(reg_)) {
MOZ_ASSERT(address.base != StackPointer);
masm->push(eax);
if (read)
masm->mov(reg_, eax);
}
}
~AutoEnsureByteRegister() {
if (!GeneralRegisterSet(Registers::SingleByteRegs).has(reg_)) {
if (!read_)
masm->mov(eax, reg_);
masm->pop(eax);
}
}
Register reg() {
if (!GeneralRegisterSet(Registers::SingleByteRegs).has(reg_))
return eax;
return reg_;
}
};
void load8ZeroExtend(const Address &src, Register dest) {
movzbl(Operand(src), dest);
}
@ -662,11 +700,16 @@ class MacroAssemblerX86Shared : public Assembler
void load8SignExtend(const BaseIndex &src, Register dest) {
movsbl(Operand(src), dest);
}
template <typename S, typename T>
void store8(const S &src, const T &dest) {
template <typename T>
void store8(Imm32 src, const T &dest) {
movb(src, Operand(dest));
}
template <typename T>
void store8(Register src, const T &dest) {
AutoEnsureByteRegister ensure(this, dest, src, /* read = */ true);
movb(ensure.reg(), Operand(dest));
}
template <typename T>
void compareExchange8ZeroExtend(const T &mem, Register oldval, Register newval, Register output) {
MOZ_ASSERT(output == eax);
MOZ_ASSERT(newval == ebx || newval == ecx || newval == edx);