Hi Matthias, Yes, thank you! I am porting your pacth to risc-v. 在2023年11月13日星期一 UTC+8 19:41:33<[email protected]> 写道：
> Hi Yahan, > > Yes, this happens in a reducer introduced a few days ago here > <https://chromium-review.googlesource.com/c/v8/v8/+/4994354/11/src/compiler/turboshaft/load-simplification-reducer.h> > . > In Turbofan, a load is a simple operation that represents *(base + index) > in Turboshaft, a load expresses *(base + index * element_size + offset). > This is somewhat close to loads in e.g. x86-64 but doesn't seem to map > that greatly to e.g. arm64 where a load is a simpler / more restricted > instruction. > There are two options to solve this: > a) During instruction selection map the complex load to a sequence of > machine instructions. > b) Before instruction selection, lower the "complex" loads to simpler > operations that are closer to the target machine. > (a) is probably the cleaner design as it means that the optimizations are > machine-independent (which already isn't true in many other cases, like > count-leading-zeros and other operations that will directly be replaced by > something else very early if the target machine doesn't support these). > The advantage of (b) is that any subsequent loads with the same base + > index * element_size but a different offset can profit from global value > numbering to not having to repeat this calculation multiple times. > > That being said, please note that --turboshaft-wasm-instruction-selection > is a highly experimental flag that currently doesn't support much else than > what is covered in this single mjsunit test. > It will take multiple weeks to get it to a state where it's > feature-complete. > It might also be a bit unfortunate that this is done during a phase called > WasmDeadCodeElimination while this isn't about dead code. The issue is that > every additional phase has a significant impact on both compile time and > binary size. For the time of this being experimental it might however be a > good idea to move it into its own phase. > > Does this help? Do you see an issue in this transformation? (Note that > prior to this similar modifications would happen when translating the > Turboshaft load to a Turbofan load in recreate-schedule.cc > <https://source.chromium.org/chromium/chromium/src/+/main:v8/src/compiler/turboshaft/recreate-schedule.cc;l=1034> > . > > Best regards, > Matthias > > > On Mon, Nov 13, 2023 at 12:19 PM Yahan Lu <[email protected]> wrote: > >> >> ----- V8.TFTurboshaftWasmOptimize ----- >> >> MERGE B0 >> 0: Parameter()[1] >> 1: StackCheck()[WebAssembly, function-entry] >> 2: Constant()[word64: 1] >> 3: WordBinop(#0, #2)[BitwiseAnd, Word64] >> 4: Constant()[word64: 0] >> 5: Equal(#3, #4)[Word64] >> 6: Constant()[word32: 0] >> 7: Branch(#5)[B2, B1, False] >> >> BLOCK B1 <- B0 >> 10: Load *(#0) [tagged base, TaggedPointer] >> 11: Load *(#10 + 12) [tagged base, Uint16, offset: 12] >> 12: Constant()[word32: 128] >> 13: Comparison(#11, #12)[UnsignedLessThan, Word32] >> 14: Goto()[B3] >> >> BLOCK B2 <- B0 >> 15: Goto()[B3] >> >> MERGE B3 <- B1, B2 >> 16: Phi(#13, #6)[Word32] >> 17: Return(#6, #16) >> >> ----- V8.TFTurboshaftWasmDeadCodeElimination ----- >> >> MERGE B0 >> 0: Parameter()[1] >> 1: Constant()[word64: 1] >> 2: WordBinop(#0, #1)[BitwiseAnd, Word64] >> 3: Constant()[word64: 0] >> 4: Equal(#2, #3)[Word64] >> 5: Constant()[word32: 0] >> 6: Branch(#4)[B2, B1, False] >> >> BLOCK B1 <- B0 >> 9: TaggedBitcast(#0)[Tagged, Word64] >> 10: Load *(#9 - 1) [raw, TaggedPointer, offset: -1] >> 11: TaggedBitcast(#10)[Tagged, Word64] >> 12: Load *(#11 + 11) [raw, Uint16, offset: 11] >> 13: Constant()[word32: 128] >> 14: Comparison(#12, #13)[UnsignedLessThan, Word32] >> 15: Goto()[B3] >> >> >> On Block B1 >> Before TFTurboshaftWasmDeadCodeElimination >> 10: Load *(#0) [tagged base, TaggedPointer] >> After: >> 9: TaggedBitcast(#0)[Tagged, Word64] >> 10: Load *(#9 - 1) [raw, TaggedPointer, offset: -1] >> >> Is it changed by TFTurboshaftWasmDeadCodeElimination? >> I set constexpr bool trace_analysis true, >> I can't find any information about this change. >> >> cmd: >> arm64.release/d8 --test test/mjsunit/mjsunit.js >> test/mjsunit/wasm/turboshaft/instruction-selection.js >> --random-seed=-1803833885 --nohard-abort --verify-heap >> --testing-d8-test-runner --no-liftoff --no-wasm-lazy-compilation >> --experimental-wasm-stringref --turboshaft-wasm >> --turboshaft-wasm-instruction-selection --print-code --trace-turbo-graph >> --trace-turbo-filter=isString >> >> -- >> -- >> v8-dev mailing list >> [email protected] >> http://groups.google.com/group/v8-dev >> --- >> You received this message because you are subscribed to the Google Groups >> "v8-dev" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/v8-dev/0f717fd7-a31d-4d32-ae62-4a5e2d03e50dn%40googlegroups.com >> >> <https://groups.google.com/d/msgid/v8-dev/0f717fd7-a31d-4d32-ae62-4a5e2d03e50dn%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > > > -- > > Matthias Liedtke > > Software Engineer > > [email protected] > > Google Germany GmbH > > Erika-Mann-Straße 33 > > 80636 München > > Geschäftsführer: Paul Manicle, Liana Sebastian > > Registergericht und -nummer: Hamburg, HRB 86891 > > Sitz der Gesellschaft: Hamburg > > Diese E-Mail ist vertraulich. 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