This patch contains two DAGCombine:
fold vp_mul X, (splat -1), Mask, EVL -> vp_sub (splat 0), X, Mask, EVL
fold vp_mul X, (1 << C), Mask, EVL -> vp_shl X, C, Mask, EVL
Details
Details
Diff Detail
Diff Detail
- Repository
- rG LLVM Github Monorepo
| Time | Test | |
|---|---|---|
| 60,460 ms | x64 debian > Clang.CodeGen/RISCV/rvv-intrinsics-overloaded::vluxseg_mask.c Script:
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: 'RUN: at line 3'; /var/lib/buildkite-agent/builds/llvm-project/build/bin/clang -cc1 -internal-isystem /var/lib/buildkite-agent/builds/llvm-project/build/lib/clang/15.0.0/include -nostdsysteminc -triple riscv64 -target-feature +f -target-feature +d -target-feature +v -disable-O0-optnone -emit-llvm /var/lib/buildkite-agent/builds/llvm-project/clang/test/CodeGen/RISCV/rvv-intrinsics-overloaded/vluxseg_mask.c -o - | /var/lib/buildkite-agent/builds/llvm-project/build/bin/opt -S -mem2reg | /var/lib/buildkite-agent/builds/llvm-project/build/bin/FileCheck --check-prefix=CHECK-RV64 /var/lib/buildkite-agent/builds/llvm-project/clang/test/CodeGen/RISCV/rvv-intrinsics-overloaded/vluxseg_mask.c
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Event Timeline
| llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | ||
|---|---|---|
| 22858 | (style) Don't use auto unless the type is obvious (i.e. a cast<>) | |
| llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | ||
|---|---|---|
| 22861 | If one of the true/false values of the VP_SELECT is undef can we ignore the mask and EVL and return the other operand? @simoll @frasercrmck | |
| llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | ||
|---|---|---|
| 22861 | I believe so. Also for vp ops other than select or merge, if the mask is undef, we can scratch the operation entirely. If evl is undef, we can cut short to unreachable. | |
| llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | ||
|---|---|---|
| 22861 | Done, thanks. | |
| llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | ||
|---|---|---|
| 22863 | I think we should only use getSplatVector for scalable vectors. Fixed vectors should use getSplatBuildVector. | |
| 22863 | You can just call DAG.getConstant(0, SDLoc(N), VT); It will do the right thing. | |
| 22874 | DAG.getConstant(0, SDLoc(N), VT) | |
| 22882 | Same comment as above. | |
Comment Actions
@jacquesguan Thanks for working on VP optimizations! We just discussed on the VP syncup call where we want to go with this.
The thing is that this patch is essentially replicating the existing MUL DAGCombiner patterns for VP_MUL. Ideally, we would lift the existing DAGCombiner logic to work on both VP and non-VP SDNodes - automatically.
I've implemented something like this in NEC's open source LLVM stack:
https://github.com/sx-aurora-dev/llvm-project/blob/develop/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
The idea is to templatize the pattern-matching and rewriting code and instantiate that for each VP and non-VP. In essence, https://reviews.llvm.org/D92086 but on the SelectionDAG.
Would you be interested in working on a more general approach? Please contact me directly so we can get you on the VP Discord server or arrange a call to talk about this.