Summary:
Intel documentation shows the memory operand as the first operand. But we currently treat it as the second operand. Conceptually the order doesn't matter since it doesn't write memory. We have aliases to parse with the operands in either order and the isel matching is commutable.
For the register®ister form order does matter for the assembly parser. PR22995 was previously filed and fixed by changing the register®ister form from MRMSrcReg to MRMDestReg to match gas. Ideally the memory form should match by using MRMDestMem.
I believe this supercedes D38025 which was trying to switch the register®ister form back to pre-PR22995.
Reviewers: aymanmus, RKSimon, zvi
Reviewed By: aymanmus
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D38120
llvm-svn: 314639
This patch fixes bugzilla 31576 (https://llvm.org/bugs/show_bug.cgi?id=31576).
"data32" instruction prefix was not defined in the llvm.
An exception had to be added to the X86 tablegen and AsmPrinter because both "data16" and "data32" are encoded to 0x66 (but in different modes).
Differential Revision: https://reviews.llvm.org/D28468
llvm-svn: 292352
Moves of a value to a segment register from a 16-bit register is
equivalent to one from it's corresponding 32-bit register. Match gas's
behavior and rewrite instructions to the shorter of equivalent forms.
Reviewers: rnk, ab
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D23166
llvm-svn: 278031
It seems there is no separate instruction class for having AdSize *and*
OpSize bits set, which is required in order to disambiguate between all
these instructions. So add that to the disassembler.
Hm, perhaps we do need an AdSize16 bit after all?
llvm-svn: 198759
Where "where possible" means that it's an immediate value and it's below
0x10000. In fact GAS will either truncate or error with larger values,
and will insist on using the addr32 prefix to get 32-bit addressing. So
perhaps we should do that, in a later patch.
llvm-svn: 198758
JCXZ should have the 0x67 prefix only if we're in 32-bit mode, so make that
appropriately conditional. And JECXZ needs the prefix instead.
llvm-svn: 198757
I couldn't see how to do this sanely without splitting RETQ from RETL.
Eric says: "sad about the inability to roundtrip them now, but...".
I have no idea what that means, but perhaps it wants preserving in the
commit comment.
llvm-svn: 198756
This fixes the bulk of 16-bit output, and the corresponding test case
x86-16.s now looks mostly like the x86-32.s test case that it was
originally based on. A few irrelevant instructions have been dropped,
and there are still some corner cases to be fixed in subsequent patches.
llvm-svn: 198752
The 0x66 prefix toggles between 16-bit and 32-bit addressing mode.
So in 32-bit mode it is used to switch to 16-bit addressing mode for the
following instruction, while in 16-bit mode it's the other way round — it's
used to switch to 32-bit mode instead.
Thus, emit the 0x66 prefix byte for OpSize only in 32-bit (and 64-bit) mode,
and introduce a new OpSize16 bit which is used in 16-bit mode instead.
This is just the basic infrastructure for that change; a subsequent patch
will add the new OpSize16 bit to the 32-bit instructions that need it.
Patch from David Woodhouse.
llvm-svn: 198586
This is not really expected to work right yet. Mostly because we will
still emit the OpSize (0x66) prefix in all the wrong places, along with
a number of other corner cases. Those will all be fixed in the subsequent
commits.
Patch from David Woodhouse.
llvm-svn: 198584
