search for: volatile_copi

On 02/25/2016 06:14 PM, Matthias Braun via llvm-dev wrote: > 1) The value read from a reserved register cannot be predicted. Reading a reserved register twice may each time produce a different result. This seems broken to me that treating another copy should be assumed to produce a different result. This seems like it should be optimized, and have a special volatile_copy instruction for the

Let's try this again after some longer offline discussions: = Reserved Registers = The primary use of reserved registers is to hold values required by runtime conventions. Typical examples are the stack pointer, frame pointer maybe TLS base address, GOT address ... Zero registers and program counters are an odd special case for which we may be able to provide looser rules. == Rules == 1)

> On Feb 26, 2016, at 1:54 PM, Matthias Braun <mbraun at apple.com> wrote: > > Let's try this again after some longer offline discussions: > > = Reserved Registers = > The primary use of reserved registers is to hold values required by runtime conventions. Typical examples are the stack pointer, frame pointer maybe TLS base address, GOT address ... > Zero registers

Lately I have had a few discussions of what it means for a register to be unallocatable or reserved. As this comes up every now and again and I often struggled answering such questions I decided to write down some definite rules and codify the current usage and assumptions. I plan to put the rules below into the doxygen comments of MachineRegisterInfo etc. And I also hope that people will correct