en Copyright 2015 Java http://172.16.0.5:8080/history/llvm-project-15.0.7/llvm/test/CodeGen/BPF/CORE/simplifypatable-nullptr.ll#497a5f04 [BPF] Fix a bug in BPFMISimplifyPatchable passLLVM BPF pass SimplifyPatchable is used to do necessarycode conversion for CO-RE operations. When studying bpfselftest 'exhandler', I found a corner case not handled properly.The following is the C code, modified from original 'exhandler'code. int g; int test(struct t1 *p) { struct t2 *q = p->q; if (q) return 0; struct t3 *f = q->f; if (!f) g = 5; return 0; }For code: struct t3 *f = q->f; if (!f) ...The IR before BPFMISimplifyPatchable pass looks like: %5:gpr = LD_imm64 @"llvm.t2:0:8$0:1" %6:gpr = LDD killed %5:gpr, 0 %7:gpr = LDD killed %6:gpr, 0 JNE_ri killed %7:gpr, 0, %bb.3 JMP %bb.2Note that compiler knows q = 0 based dataflow and value analysis.The correct generated code after the pass should be %5:gpr = LD_imm64 @"llvm.t2:0:8$0:1" %7:gpr = LDD killed %5:gpr, 0 JNE_ri killed %7:gpr, 0, %bb.3 JMP %bb.2But the current implementation did further optimization for theabove code and generates %5:gpr = LD_imm64 @"llvm.t2:0:8$0:1" JNE_ri killed %5:gpr, 0, %bb.3 JMP %bb.2which is incorrect.This patch added a cache to remember those load insns not associatedwith CO-RE offset value and will skip these load insns duringtransformation.Differential Revision: https://reviews.llvm.org/D123883 List of files: /llvm-project-15.0.7/llvm/test/CodeGen/BPF/CORE/simplifypatable-nullptr.ll Mon, 04 Apr 2022 18:39:51 +0000 Peter Klausler <pklausler@nvidia.com>