[SOL] Remove lddw instruction
#74
Conversation
| (outs GPR:$dst), | ||
| (ins GPR:$src2, u64imm:$imm), | ||
| "hor64 $dst, $imm", | ||
| []>; |
There was a problem hiding this comment.
While this isn't incorrect per-se, we do not need two different instructions defined for each case (different selection patterns are enough). Optional change.
There was a problem hiding this comment.
I couldn't see how to do it with patterns. The two instructions have different operand types, and I get and error if I use only HOR.
llvm/lib/Target/SBF/SBFInstrInfo.td
Outdated
| // These instructions copy the value 0x1122334455667788 to a register. | ||
| def : Pat<(i64 imm:$imm), | ||
| (HOR (MOV_32_64_imm (i32 (Lower64 $imm))), | ||
| (i32 (Upper64 $imm)))>, Requires<[SBFv2]>; |
There was a problem hiding this comment.
Note that since we now generate the pair rather than lddw, there are opportunities for minor optimizations here. For example, if the upper 32-bits is clear, we only need to emit one instruction (and similar patterns).
It isn't important for this patch, but a follow-up patch might add those tweaks and corresponding unit tests. Given the absurdly long instruction word size of BPF/SBF (and the code size restrictions of Solana contracts/programs), eliminating redundant instructions like this is a good idea.
There was a problem hiding this comment.
I'll do this in a follow-up PR.
LucasSte
merged commit 4ca616d
into
anza-xyz:solana-rustc/16.0-2023-06-05
* Remove lddw instruction * Add suggestions
* Remove lddw instruction * Add suggestions
* Remove lddw instruction * Add suggestions
* Remove lddw instruction * Add suggestions
This PR represents the third task in solana-labs/solana#34250. It removes the
lddwinstructions and configures the SBF backend to generatemov32andhor64for loading 64-bit immediates.It is the corresponding change in LLVM for solana-labs/rbpf#486 and solana-labs/rbpf#496.