목록분류 전체보기 (139)

Why should I know this?

computeKnownBits & KnownBits 관련 예제

computeKnownBits https://llvm.org/doxygen/ValueTracking_8cpp.html#a903bd19e9d31beff55b22fe86111639e Determine which bits of V are known to be either zero or one and return them. void computeKnownBits (const Value *V, KnownBits &Known, const DataLayout &DL, unsigned Depth=0, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr, bool UseInstrInfo=true) Dete..
LLVM-STUDY 2023. 12. 5. 00:25
[TODO] GVN

* 다른 이슈 스터디 차원에서 먼저 일부 GVN 로직을 다룹니다. ;*** IR Dump After MergedLoadStoreMotionPass on test1 *** ; Function Attrs: mustprogress nofree norecurse nosync nounwind readnone uwtable willreturn define dso_local zeroext i1 @test1(i1 noundef zeroext %a, i1 noundef zeroext %b) local_unnamed_addr #0 { entry: %or5 = or i1 %a, %b br i1 %or5, label %cond.true, label %cond.false cond.true: ; preds = %entry %xo..
LLVM-STUDY/PASS 2023. 11. 24. 23:51
Simplification Comparison for (a | b) ? (a ^ b) : (a & b) etc. (Clang13 vs Clang trunk

이번에 살펴볼 이슈는 이겁니다. https://github.com/llvm/llvm-project/issues/71792 Simplification Comparison for `(a | b) ? (a ^ b) : (a & b)` etc. (Clang13 vs Clang trunk) · Issue #71792 · llvm/llvm-project Consider the following six functions. https://godbolt.org/z/cTsd43jhh bool test1(bool a, bool b) { return (a | b) ? (a ^ b) : (a & b); } bool test2(bool a, bool b) { return (a | b) ? (a & b) : (a ^... gith..
LLVM-STUDY/PATCH 2023. 11. 12. 06:23
[MemCpyOpt] The store instruction should not be removed by DSE.

패치 링크 : https://github.com/llvm/llvm-project/issues/70578 [MemCpyOpt] The store instruction should not be removed by DSE. · Issue #70578 · llvm/llvm-project This IR is reduced from rust-lang/rust#116976. declare void @f_byval(ptr byval(i32)) declare void @llvm.memcpy.p0.p0.i64(ptr, ptr, i64, i1) define void @byval_param_noalias_metadata(ptr align 4 byv... github.com 문제 IR https://llvm.godbolt.or..
LLVM-STUDY/PATCH 2023. 11. 7. 18:24
byval

https://discourse.llvm.org/t/how-does-byval-work/62397/3 How does byval work? Yeah I’m actually looking for the behavior as it is now. I’m not implementing a new backend, I’m trying to see if byval passes it on the stack on all platforms (arm, aarch64, x86_64, i386, etc), so I was wondering if there is a default behavior here discourse.llvm.org
LLVM-STUDY 2023. 11. 7. 18:10
[TODO] MemorySSAAnalysis

(gdb) bt #0 0x00005555562eebc6 in llvm::BatchAAResults::getModRefInfo (this=0x7fffffffb980, I=0x55555ceb46a0, OptLoc=std::optional [no contained value]) at /home/m/llvm-project/llvm/include/llvm/Analysis/AliasAnalysis.h:641 #1 0x000055555657a3de in llvm::MemorySSA::createNewAccess (this=0x55555ce56230, I=0x55555ceb46a0, AAP=0x7fffffffb980, Template=0x0) at /home/m/llvm-project/llvm/lib/Analysis/..
LLVM-STUDY/TODO 2023. 11. 7. 17:36
[TODO] Metadata & Attribute

https://llvm.org/devmtg/2016-11/Slides/Finkel-IntrinsicsMetadataAttributes.pdf
LLVM-STUDY/TODO 2023. 11. 6. 23:47
[TODO] MemorySSA = MSSA

https://llvm.org/docs/MemorySSA.html MemorySSA — LLVM 18.0.0git documentation MemorySSA is an analysis that can be built for any arbitrary function. When it’s built, it does a pass over the function’s IR in order to build up its mapping of MemoryAccesses. You can then query MemorySSA for things like the dominance relation betwee llvm.org
LLVM-STUDY/TODO 2023. 11. 6. 15:59
LLVM middle-end 최적화 관련 주의점(?)

1. 당면한 문제에 `몰입`도 중요하지만 더 큰 구조를 생각하는 것도 중요하다. 제가 경험했던 패치 https://reviews.llvm.org/D153752 ⚙ D153752 [InstSimplify] Fold icmp comparing GEPs with local allocation This revision is now accepted and ready to land. reviews.llvm.org 최근에 살펴본 패치 https://die4taoam.tistory.com/136 [InstSimplify] Fold (a != 0) ? abs(a) : 0 https://github.com/llvm/llvm-project/pull/70305 [InstSimplify] Fold (a != 0) ? abs(a..
LLVM-STUDY/PATCH 2023. 11. 6. 15:41
Memcpyopt crashes with simple IR

이번에 살펴볼 패치는 매우 짧아서 좋은 패치 입니다. 패치의 링크 https://github.com/llvm/llvm-project/issues/71183 Memcpyopt crashes with simple IR · Issue #71183 · llvm/llvm-project target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128-ni:10:11:12:13" target triple = "x86_64-unknown-linux-gnu" define void @"julia_#36#f_439"() { top: call v... github.com 최초에 문제가 발생하는 IR 은 다음과 같습니다. def..
LLVM-STUDY/PATCH 2023. 11. 6. 15:37
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