diff --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp --- a/llvm/lib/CodeGen/MachineSink.cpp +++ b/llvm/lib/CodeGen/MachineSink.cpp @@ -105,6 +105,9 @@ using AllSuccsCache = std::map>; + // Remember debug uses of vregs seen, so we know what to sink out of blocks. + DenseMap> SeenDbgUsers; + public: static char ID; // Pass identification @@ -132,6 +135,7 @@ private: bool ProcessBlock(MachineBasicBlock &MBB); + void ProcessDbgInst(MachineInstr &MI); bool isWorthBreakingCriticalEdge(MachineInstr &MI, MachineBasicBlock *From, MachineBasicBlock *To); @@ -153,8 +157,14 @@ MachineBasicBlock *To, bool BreakPHIEdge); bool SinkInstruction(MachineInstr &MI, bool &SawStore, - AllSuccsCache &AllSuccessors); + + /// If we sink a COPY inst, some debug users of it's destination may no + /// longer be dominated by the COPY, and will eventually be dropped. + /// This is easily rectified by forwarding the non-dominated debug uses + /// to the copy source. + void SalvageUnsunkDebugUsersOfCopy(MachineInstr &, + MachineBasicBlock *TargetBlock); bool AllUsesDominatedByBlock(unsigned Reg, MachineBasicBlock *MBB, MachineBasicBlock *DefMBB, bool &BreakPHIEdge, bool &LocalUse) const; @@ -367,8 +377,11 @@ if (!ProcessedBegin) --I; - if (MI.isDebugInstr()) + if (MI.isDebugInstr()) { + if (MI.isDebugValue()) + ProcessDbgInst(MI); continue; + } bool Joined = PerformTrivialForwardCoalescing(MI, &MBB); if (Joined) { @@ -384,9 +397,23 @@ // If we just processed the first instruction in the block, we're done. } while (!ProcessedBegin); + SeenDbgUsers.clear(); + return MadeChange; } +void MachineSinking::ProcessDbgInst(MachineInstr &MI) { + // When we see DBG_VALUEs for registers, record any vreg it reads, so that + // we know what to sink if the vreg def sinks. + assert(MI.isDebugValue() && "Expected DBG_VALUE for processing"); + + MachineOperand &MO = MI.getOperand(0); + if (!MO.isReg() || !MO.getReg().isVirtual()) + return; + + SeenDbgUsers[MO.getReg()].push_back(&MI); +} + bool MachineSinking::isWorthBreakingCriticalEdge(MachineInstr &MI, MachineBasicBlock *From, MachineBasicBlock *To) { @@ -731,22 +758,13 @@ MBP.LHS.getReg() == BaseOp->getReg(); } -/// Sink an instruction and its associated debug instructions. If the debug -/// instructions to be sunk are already known, they can be provided in DbgVals. +/// Sink an instruction and its associated debug instructions. static void performSink(MachineInstr &MI, MachineBasicBlock &SuccToSinkTo, MachineBasicBlock::iterator InsertPos, - SmallVectorImpl *DbgVals = nullptr) { + SmallVectorImpl &DbgValuesToSink) { const MachineRegisterInfo &MRI = MI.getMF()->getRegInfo(); const TargetInstrInfo &TII = *MI.getMF()->getSubtarget().getInstrInfo(); - // If debug values are provided use those, otherwise call collectDebugValues. - SmallVector DbgValuesToSink; - if (DbgVals) - DbgValuesToSink.insert(DbgValuesToSink.begin(), - DbgVals->begin(), DbgVals->end()); - else - MI.collectDebugValues(DbgValuesToSink); - // If we cannot find a location to use (merge with), then we erase the debug // location to prevent debug-info driven tools from potentially reporting // wrong location information. @@ -929,7 +947,25 @@ while (InsertPos != SuccToSinkTo->end() && InsertPos->isPHI()) ++InsertPos; - performSink(MI, *SuccToSinkTo, InsertPos); + // Collect debug users of any vreg that this inst defines. + SmallVector DbgUsersToSink; + for (auto &MO : MI.operands()) { + if (!MO.isReg() || !MO.isDef() || !MO.getReg().isVirtual()) + continue; + if (!SeenDbgUsers.count(MO.getReg())) + continue; + + auto &Users = SeenDbgUsers[MO.getReg()]; + DbgUsersToSink.insert(DbgUsersToSink.end(), Users.begin(), Users.end()); + } + + // After sinking, some debug users may not be dominated any more. If possible, + // copy-propagate their operands. As it's expensive, don't do this if there's + // no debuginfo in the program. + if (MI.getMF()->getFunction().getSubprogram() && MI.isCopy()) + SalvageUnsunkDebugUsersOfCopy(MI, SuccToSinkTo); + + performSink(MI, *SuccToSinkTo, InsertPos, DbgUsersToSink); // Conservatively, clear any kill flags, since it's possible that they are no // longer correct. @@ -944,6 +980,41 @@ return true; } +void MachineSinking::SalvageUnsunkDebugUsersOfCopy( + MachineInstr &MI, MachineBasicBlock *TargetBlock) { + assert(MI.isCopy()); + assert(MI.getOperand(1).isReg()); + + // Enumerate all users of vreg operands that are def'd. Skip those that will + // be sunk. For the rest, if they are not dominated by the block we will sink + // MI into, propagate the copy source to them. + SmallVector DbgDefUsers; + const MachineRegisterInfo &MRI = MI.getMF()->getRegInfo(); + for (auto &MO : MI.operands()) { + if (!MO.isReg() || !MO.isDef() || !MO.getReg().isVirtual()) + continue; + for (auto &User : MRI.use_instructions(MO.getReg())) { + if (!User.isDebugValue() || DT->dominates(TargetBlock, User.getParent())) + continue; + + // If is in same block, will either sink or be use-before-def. + if (User.getParent() == MI.getParent()) + continue; + + assert(User.getOperand(0).isReg() && + "DBG_VALUE user of vreg, but non reg operand?"); + DbgDefUsers.push_back(&User); + } + } + + // Point the users of this copy that are no longer dominated, at the source + // of the copy. + for (auto *User : DbgDefUsers) { + User->getOperand(0).setReg(MI.getOperand(1).getReg()); + User->getOperand(0).setSubReg(MI.getOperand(1).getSubReg()); + } +} + //===----------------------------------------------------------------------===// // This pass is not intended to be a replacement or a complete alternative // for the pre-ra machine sink pass. It is only designed to sink COPY @@ -1253,7 +1324,7 @@ // block. clearKillFlags(MI, CurBB, UsedOpsInCopy, UsedRegUnits, TRI); MachineBasicBlock::iterator InsertPos = SuccBB->getFirstNonPHI(); - performSink(*MI, *SuccBB, InsertPos, &DbgValsToSink); + performSink(*MI, *SuccBB, InsertPos, DbgValsToSink); updateLiveIn(MI, SuccBB, UsedOpsInCopy, DefedRegsInCopy); Changed = true; diff --git a/llvm/test/DebugInfo/MIR/X86/machinesink.mir b/llvm/test/DebugInfo/MIR/X86/machinesink.mir new file mode 100644 --- /dev/null +++ b/llvm/test/DebugInfo/MIR/X86/machinesink.mir @@ -0,0 +1,105 @@ +# RUN: llc -mtriple=x86_64-unknown-unknown -run-pass=machine-sink -o - %s | FileCheck %s +# Check various things when we sink machine instructions: +# a) DBG_VALUEs should sink with defs +# b) Undefs should be left behind +# c) DBG_VALUEs not immediately following the defining inst should sink too +# d) If we generate debug-use-before-defs through sinking, and can copy +# propagate to a different value, we should do that. +--- | + target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" + target triple = "x86_64-unknown-linux-gnu" + + @x = common local_unnamed_addr global i32 0, align 4, !dbg !0 + + ; Function Attrs: noreturn nounwind uwtable + define void @Process(i32* nocapture readonly %p) local_unnamed_addr !dbg !9 { + ; Stripped + entry: + br label %nou + nou: + br label %exit + exit: + ret void + } + + ; Function Attrs: nounwind readnone + declare void @llvm.dbg.value(metadata, i64, metadata, metadata) + + !llvm.dbg.cu = !{!1} + !llvm.module.flags = !{!6, !7} + !llvm.ident = !{!8} + + !0 = !DIGlobalVariableExpression(var: !DIGlobalVariable(name: "x", scope: !1, file: !2, line: 1, type: !5, isLocal: false, isDefinition: true), expr: !DIExpression()) + !1 = distinct !DICompileUnit(language: DW_LANG_C99, file: !2, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !3, globals: !4) + !2 = !DIFile(filename: "t.c", directory: "") + !3 = !{} + !4 = !{!0} + !5 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) + !6 = !{i32 2, !"Dwarf Version", i32 4} + !7 = !{i32 2, !"Debug Info Version", i32 3} + !8 = !{!"clang version 4.0.0 "} + !9 = distinct !DISubprogram(name: "Process", scope: !2, file: !2, line: 2, type: !10, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: true, unit: !1, retainedNodes: !15) + !10 = !DISubroutineType(types: !11) + !11 = !{null, !12} + !12 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !13, size: 64) + !13 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !14) + !14 = !DIBasicType(name: "unsigned int", size: 32, encoding: DW_ATE_unsigned) + !15 = !{!16} + !16 = !DILocalVariable(name: "p", arg: 1, scope: !9, file: !2, line: 2, type: !12) + !17 = !DIExpression() + !18 = !DILocation(line: 2, column: 34, scope: !9) + !28 = !DILexicalBlockFile(scope: !9, file: !2, discriminator: 1) + + ; CHECK: [[VARNUM:![0-9]+]] = !DILocalVariable(name: "p", + +... +--- +name: Process +tracksRegLiveness: true +liveins: + - { reg: '$rdi', virtual-reg: '%2' } + - { reg: '$rsi', virtual-reg: '%2' } +body: | + bb.0.entry: + successors: %bb.1.nou(0x80000000), %bb.2.exit + liveins: $rdi, $esi + + ; This block should have the vreg copy sunk from it, the DBG_VALUE with it, + ; and a copy-prop'd DBG_VALUE left over. + ; CHECK-LABEL: bb.0.entry: + ; CHECK: [[ARG0VREG:%[0-9]+]]:gr64 = COPY $rdi + ; CHECK-NEXT: CMP32ri $esi, 0 + ; CHECK-NEXT: DBG_VALUE [[ARG0VREG]], $noreg, [[VARNUM]] + ; CHECK-NEXT: JCC_1 %bb.1, 4 + ; CHECK-NEXT: JMP_1 + + %2:gr64 = COPY $rdi + %5:gr64 = COPY %2 + CMP32ri $esi, 0, implicit-def $eflags + DBG_VALUE %5, $noreg, !16, !17, debug-location !18 + JCC_1 %bb.1.nou, 4, implicit $eflags + JMP_1 %bb.2.exit + + bb.1.nou: + successors: %bb.2.exit(0x80000000) + + ; This block should receive the sunk copy and DBG_VALUE + ; CHECK-LABEL: bb.1.nou: + ; CHECK: [[SUNKVREG:%[0-9]+]]:gr64 = COPY [[ARG0VREG]] + ; CHECK-NEXT: DBG_VALUE [[SUNKVREG]], $noreg, [[VARNUM]] + ; CHECK-NEXT: ADD64ri8 + ; CHECK-NEXT: JMP_1 + %1:gr64 = ADD64ri8 %5, 4, implicit-def dead $eflags + JMP_1 %bb.2.exit + + bb.2.exit: + ; The DBG_VALUE below should have its operand copy-propagated after + ; the copy to %5 is sunk. + ; CHECK-LABEL: bb.2.exit: + ; CHECK: DBG_VALUE [[ARG0VREG]], $noreg, [[VARNUM]] + ; CHECK-NEXT: $rax = MOV64rr [[ARG0VREG]] + ; CHECK-NEXT: RET 0 + DBG_VALUE %5, _, !16, !17, debug-location !18 + $rax = MOV64rr %2 + RET 0 +...