[PATCH] D120592: [X86] Fix handling of Address-Size override prefix

[Kan Shengchen via Phabricator via llvm-commits]

skan added a comment.

In D120592#3348246 <https://reviews.llvm.org/D120592#3348246>, @craig.topper wrote:

> In D120592#3348216 <https://reviews.llvm.org/D120592#3348216>, @skan wrote:
>
>> I think this patch is totally wrong. We need address size override prefix only when the instruction has a memory operand.The address-size override prefix (67H) allows programs to switch between 16- and 32-bit addressing. Either size can be the default; the prefix selects the non-default size. Using this prefix and/or other undefined opcodes when operands for the instruction do not reside in memory is reserved; such use may cause unpredictable behavior.  Whether a instruction need ASZ should be included in the definition of the instruction in tablgen.
>
> I believe example test case is supported by gas and callq does use address size. What syntax should be used instead?

This test case is misleading.  LLVM-MC can pass the test case w/o this patch b/c an expicit prefix is added. However, this callq does not need a ASZ at all.


Repository:
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  https://reviews.llvm.org/D120592/new/

https://reviews.llvm.org/D120592