[llvm-bugs] [Bug 13801] llvm-mc does not parse the .w suffix on ldr and str instructions

via llvm-bugs llvm-bugs at lists.llvm.org
Mon Dec 4 11:29:26 PST 2017


Gordon Keiser <codeman.consulting at gmail.com> changed:

           What    |Removed                     |Added
             Status|NEW                         |RESOLVED
                 CC|                            |codeman.consulting at gmail.co
                   |                            |m
         Resolution|---                         |INVALID

--- Comment #2 from Gordon Keiser <codeman.consulting at gmail.com> ---
Encoding T4 ARMv6T2, ARMv7
LDR<c> <Rt>, [<Rn>, #-<imm8>]
LDR<c> <Rt>, [<Rn>], #+/-<imm8>
LDR<c> <Rt>, [<Rn>, #+/-<imm8>]!

The T4 encoding doesn't use the .W modifier, that indicates that T3 should be
used, according to ARM manuals.  

T3 specifies .W so that forces generation of it. 

Encoding T3 ARMv6T2, ARMv7
LDR<c>.W <Rt>, [<Rn>{, #<imm12>}]

In addition T3 zero-extends an imm12 and is incapable of subtraction.  T4 has a
sign bit.

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