The s_singleuse_vdst instruction is used to mark regions of instructions
that produce values that have only one use.
Certain instructions take more than one cycle to execute, resulting in
regions being incorrectly marked.
This patch excludes these multi-cycle instructions from being marked as
either producing single use values or consuming single use values
or both depending on the instruction.
Previously each single use producer would be marked with a
"S_SINGLEUSE_VDST 1" instruction. This patch adds support for
larger immediates that encode multiple single use producers into
one S_SINGLEUSE_VDST instruction.
Previously, multiple uses of a register within the same instruction were
being counted as multiple uses. This has been corrected to
only count as a single use as per the specification allowing for
more optimisation candidates.
Add support for emitting GFX11.5 s_singleuse_vdst instructions. This is
a power saving feature whereby the compiler can annotate VALU
instructions whose results are known to have only a single use, so the
hardware can in some cases avoid writing the result back to VGPR RAM.
To begin with the pass is disabled by default because of one missing
feature: we need an exclusion list of opcodes that never qualify as
single-use producers and/or consumers. A future patch will implement
this and enable the pass by default.
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Co-authored-by: Scott Egerton <scott.egerton@amd.com>
