通过LoopRotate (loop-rotate) pass可对loop进行rotate(调转)操作,这将使原loop转换为do/while的loop形式,其实现位于LoopRotation.h文件中。例如: voidtest(intn){for(inti=0;i<n;i+=1)// Loop body} 将被转换为: voidtest(intn){inti=0;do{// Loop bodyi+=1;}while(i<n);} 注意:此变换唯有在...
而 LLVM 当中有两种 canonical loop 的格式,分别是 simplified 格式和 rotated 格式(关于 canonical 的概念可以翻翻我之前写的文章)。 一开始是大部分循环的 pass 都需要依赖 simplified 格式,不过也分出了派系,一些 pass 则需要 rotated 格式来进行分析,rotated 格式是可转换的,官网对于 rotated 格式还标着双引...
DefaultRotationThreshold+: 0;const DataLayout &DL = L.getHeader()->getDataLayout(); const SimplifyQuery SQ = getBestSimplifyQuery(AR, DL);diff --git a/llvm/test/Transforms/LoopRotate/minsize-disable.ll b/llvm/test/Transforms/LoopRotate/minsize-disable.llnew file mode 100644 index 0000000000000...
loop-mssa(loop-instsimplify,loop-simplifycfg,licm<no-allowspeculation>,loop-rotate,licm<allowspeculation>,simple-loop-unswitch<nontrivial;trivial>,loop-flatten),simplifycfg<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;no-switch-to-lookup;keep-loops;no-hoist-common-insts;no-...
std::unique_ptr<llvm::legacy::PassManager>pass_manager(newllvm::legacy::PassManager());pass_manager->add(llvm::createFunctionInliningPass());pass_manager->add(llvm::createLoopRotatePass());pass_manager->add(llvm::createLICMPass());pass_manager->add(llvm::createInstructionCombiningPass...
2000年,伊利诺伊大学厄巴纳-香槟分校(University of Illinois at Urbana-Champaign 简称UIUC)这所享有世界声望的一流公立研究型大学的 Chris Lattner(他的 twitter @clattner_llvm ) 开发了一个叫作 Low Level Virtual M...
优化的方法不一而足，总体上将有以下几类：1）精简操作指令；2）尽量满足 cpu 的流水操作；3）通过对...
I don’t know of any superoptimizer that targets code containing loops. There seem to be two obstacles. First, the search space may become problematically large. Second, the straightforward approach to encoding a loop in SMT — to unroll it a few times — is unsound. Can I use an SMT ...
Stack dump: 0. Program arguments: /opt/llvm-19/bin/opt -O3 -S bug.ll 1. Running pass "function<eager-inv>(float2int,lower-constant-intrinsics,chr,loop(loop-rotate,loop-deletion),loop-distribute,inject-tli-mappings,loop-vectorize<no-interleave-forced-only;no-vectorize-forced-only;>,infer-al...
We can do this because we still need to reshuffle smaller subgraph when buildiong operands for the graph nodes with lasrger vectorization factor, we can rotate just subgraph, not the whole graph. The second step (bottom-to-top) scans through the leaves and tries to detect the users of the...