On April 21, 2020 12:26:12 PM PDT, Xi Wang <xi.wang@xxxxxxxxx> wrote: >On Tue, Apr 21, 2020 at 10:39 AM H. Peter Anvin <hpa@xxxxxxxxx> wrote: >> x32 is not x86-32. In Linux we generally call the latter "i386". > >Agreed. Most of the previous patches to this file use "x32" and this >one just wanted to be consistent. > >> C7 /0 imm32 is a valid instruction on i386. However, it is also >> inefficient when the destination is a register, because B8+r imm32 is >> equivalent, and when the value is zero, XOR is indeed more efficient. >> >> The real error is using EMIT3() instead of EMIT2_off32(), but XOR is >> more efficient. However, let's make the bug statement *correct*, or >it >> is going to confuse the Hades out of people in the future. > >I don't see how the bug statement is incorrect, which merely points >out that "C7 C0 0" is an invalid instruction, regardless of whether >the JIT intended to emit C7 /0 imm32, B8+r imm32, 31 /r, 33 /r, or any >other equivalent form. C7 C0 0 is *not* an invalid instruction, although it is incomplete. It is a different, but arguably even more serious, problem. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
