The AMDGPU target has a convention that defined all VGPRs
(execept the initial 32 argument registers) as callee-saved.
This convention is not efficient always, esp. when the callee
requiring more registers, ended up emitting a large number of
spills, even though its caller requires only a few.
This patch revises the ABI by introducing more scratch registers
that a callee can freely use.
The 256 vgpr registers now become:
32 argument registers
112 scratch registers and
112 callee saved registers.
The scratch registers and the CSRs are intermixed at regular
intervals (a split boundary of 8) to obtain a better occupancy.
Reviewers: arsenm, t-tye, rampitec, b-sumner, mjbedy, tpr
Reviewed By: arsenm, t-tye
Differential Revision: https://reviews.llvm.org/D76356
These are used in SReg_32 and when we start to use SGPR_LO16
there will be compaints that not all registers in RC support
all subreg indexes. For now it is NFC.
Unused regunits are reserved so that verifier does not complain
about missing phys reg live-ins.
Differential Revision: https://reviews.llvm.org/D78591
These are used in SReg_32 and when we start to use SGPR_LO16
there will be compaints that not all registers in RC support
all subreg indexes. For now it is NFC.
Unused regunits are reserved so that verifier does not complain
about missing phys reg live-ins.
Differential Revision: https://reviews.llvm.org/D78591
We have loads preserving low and high 16 bits of their
destinations. However, we always use a whole 32 bit register
for these. The same happens with 16 bit stores, we have to
use full 32 bit register so if high bits are clobbered the
register needs to be copied. One example of such code is
added to the load-hi16.ll.
The proper solution to the problem is to define 16 bit subregs
and use them in the operations which do not read another half
of a VGPR or preserve it if the VGPR is written.
This patch simply defines subregisters and register classes.
At the moment there should be no difference in code generation.
A lot more work is needed to actually use these new register
classes. Therefore, there are no new tests at this time.
Register weight calculation has changed with new subregs so
appropriate changes were made to keep all calculations just
as they are now, especially calculations of register pressure.
Differential Revision: https://reviews.llvm.org/D74873
This is extremly slow on AMDGPU, which has a lot of physical register
and a lot of register classes.
determineCalleeSaves, via MachineRegisterInfo::isPhysRegUsed already
added all of the super registers to the saved set.
llvm-svn: 365370
Christudasan Devadasan