Index: lib/CodeGen/LiveDebugValues.cpp =================================================================== --- lib/CodeGen/LiveDebugValues.cpp +++ lib/CodeGen/LiveDebugValues.cpp @@ -361,8 +361,18 @@ } }; - bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF, - unsigned &Reg); + /// Tests whether this instruction is a spill to a stack location. + bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF); + + /// Decide if @MI is a spill instruction and return true if it is. We use 2 + /// criteria to make this decision: + /// - Is this instruction a store to a spill slot? + /// - Is there a register operand that is both used and killed? + /// TODO: Store optimization can fold spills into other stores (including + /// other spills). We do not handle this yet (more than one memory operand). + bool isLocationSpill(const MachineInstr &MI, MachineFunction *MF, + unsigned &Reg); + /// If a given instruction is identified as a spill, return the spill location /// and set \p Reg to the spilled register. Optional isRestoreInstruction(const MachineInstr &MI, @@ -779,16 +789,8 @@ } } -/// Decide if @MI is a spill instruction and return true if it is. We use 2 -/// criteria to make this decision: -/// - Is this instruction a store to a spill slot? -/// - Is there a register operand that is both used and killed? -/// TODO: Store optimization can fold spills into other stores (including -/// other spills). We do not handle this yet (more than one memory operand). bool LiveDebugValues::isSpillInstruction(const MachineInstr &MI, - MachineFunction *MF, unsigned &Reg) { - SmallVector Accesses; - + MachineFunction *MF) { // TODO: Handle multiple stores folded into one. if (!MI.hasOneMemOperand()) return false; @@ -797,6 +799,14 @@ return false; // This is not a spill instruction, since no valid size was // returned from either function. + return true; +} + +bool LiveDebugValues::isLocationSpill(const MachineInstr &MI, + MachineFunction *MF, unsigned &Reg) { + if (!isSpillInstruction(MI, MF)) + return false; + auto isKilledReg = [&](const MachineOperand MO, unsigned &Reg) { if (!MO.isReg() || !MO.isUse()) { Reg = 0; @@ -865,7 +875,39 @@ LLVM_DEBUG(dbgs() << "Examining instruction: "; MI.dump();); - if (isSpillInstruction(MI, MF, Reg)) { + // First, if there are any DBG_VALUEs pointing at a spill slot that is + // written to, then close the variable location. The value in memory + // will have changed. + VarLocSet KillSet; + if (isSpillInstruction(MI, MF)) { + Loc = extractSpillBaseRegAndOffset(MI); + for (unsigned ID : OpenRanges.getVarLocs()) { + const VarLoc &VL = VarLocIDs[ID]; + if (VL.Kind == VarLoc::SpillLocKind && VL.Loc.SpillLocation == *Loc) { + // This location is overwritten by the current instruction -- terminate + // the open range, and insert an explicit DBG_VALUE $noreg. + // + // Doing this at a later stage would require re-interpreting all + // DBG_VALUes and DIExpressions to identify whether they point at + // memory, and then analysing all memory writes to see if they + // overwrite that memory, which is expensive. + // + // At this stage, we already know which DBG_VALUEs are for spills and + // where they are located; it's best to fix handle overwrites now. + KillSet.set(ID); + MachineInstr *NewDebugInstr = + BuildMI(*MF, VL.MI.getDebugLoc(), VL.MI.getDesc(), + VL.MI.isIndirectDebugValue(), 0, // $noreg + VL.MI.getDebugVariable(), VL.MI.getDebugExpression()); + Transfers.push_back({&MI, NewDebugInstr}); + } + } + OpenRanges.erase(KillSet, VarLocIDs); + } + + // Try to recognise spill and restore instructions that may create a new + // variable location. + if (isLocationSpill(MI, MF, Reg)) { TKind = TransferKind::TransferSpill; LLVM_DEBUG(dbgs() << "Recognized as spill: "; MI.dump();); LLVM_DEBUG(dbgs() << "Register: " << Reg << " " << printReg(Reg, TRI) Index: test/DebugInfo/MIR/X86/live-debug-values-stack-clobber.mir =================================================================== --- /dev/null +++ test/DebugInfo/MIR/X86/live-debug-values-stack-clobber.mir @@ -0,0 +1,200 @@ +# RUN: llc -mtriple=x86_64-unknown-unknown %s -o - -run-pass=livedebugvalues | FileCheck %s +# +# Fix some of PR42772. Consider the code below: the arguments are forced onto +# the stack by the FORCE_SPILL macro, and go out of liveness if the +# "bees == 2" conditional is not taken. A spill slot is then re-used to +# preserve quux over the second FORCE_SPILL, over-writing the value of either +# "a" or "b". LiveDebugValues should detect when this happens, and terminate +# stack-spill locations when they get overwritten by a new value. +# +# --------8<-------- +# #define FORCE_SPILL() \ +# __asm volatile("" : : : \ +# "rax", "rbx", "rcx", "rdx", "rsi", "rdi", "rbp", "r8", \ +# "r9", "r10", "r11", "r12", "r13", "r14", "r15") +# +# volatile int bees = 0; +# +# long int f(long int a, long int b) { +# if (bees == 12) +# return 3; +# +# FORCE_SPILL(); +# if (bees == 2) +# return a - b; +# +# int quux = sum(1, 2); +# FORCE_SPILL(); +# bees++; +# return quux; +# } +# -------->8-------- +# +# CHECK: ![[ANUM:[0-9]+]] = !DILocalVariable(name: "a" +# CHECK: ![[BNUM:[0-9]+]] = !DILocalVariable(name: "b" +# +# These variables should be spilt, +# CHECK-LABEL: bb.1.if.end: +# CHECK: MOV64mr $rsp, 1, $noreg, 16, $noreg, killed renamable $rsi +# CHECK-NEXT: DBG_VALUE $rsp, 0, ![[BNUM]], !DIExpression( +# CHECK-NEXT: MOV64mr $rsp, 1, $noreg, 8, $noreg, killed renamable $rdi +# CHECK-NEXT: DBG_VALUE $rsp, 0, ![[ANUM]], !DIExpression( +# CHECK-NEXT: INLINEASM +# +# Then the location of "a" should be terminated when overwritten +# CHECK-LABEL: bb.3.if.end3: +# CHECK: CALL64pcrel32 @sum +# CHECK-NEXT: MOV64mr $rsp, 1, $noreg, 8, $noreg, $rax +# CHECK-NEXT: DBG_VALUE $noreg, $noreg, ![[ANUM]], !DIExpression() +# CHECK-NEXT: INLINEASM + +--- | + target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" + target triple = "x86_64-unknown-linux-gnu" + + @bees = external global i32, !dbg !0 + + ; Function Attrs: noinline norecurse nounwind readnone uwtable + declare i64 @sum(i64, i64) + + ; Function Attrs: noinline nounwind uwtable + define i64 @f(i64 %a, i64 %b) !dbg !12 { + entry: + br label %if.end + if.end: + br label %if.then2 + if.then2: + br label %if.end3 + if.end3: + br label %return + return: + ret i64 0 + } + + !llvm.dbg.cu = !{!2} + !llvm.module.flags = !{!8, !9, !10} + + !0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression()) + !1 = distinct !DIGlobalVariable(name: "bees", scope: !2, file: !3, line: 6, type: !6, isLocal: false, isDefinition: true) + !2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: None) + !3 = !DIFile(filename: "pr42772.c", directory: ".") + !4 = !{} + !5 = !{!0} + !6 = !DIDerivedType(tag: DW_TAG_volatile_type, baseType: !7) + !7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) + !8 = !{i32 2, !"Dwarf Version", i32 4} + !9 = !{i32 2, !"Debug Info Version", i32 3} + !10 = !{i32 1, !"wchar_size", i32 4} + !12 = distinct !DISubprogram(name: "f", scope: !3, file: !3, line: 15, type: !13, scopeLine: 15, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !16) + !13 = !DISubroutineType(types: !14) + !14 = !{!15, !15, !15} + !15 = !DIBasicType(name: "long int", size: 64, encoding: DW_ATE_signed) + !16 = !{!17, !18, !19} + !17 = !DILocalVariable(name: "a", arg: 1, scope: !12, file: !3, line: 15, type: !15) + !18 = !DILocalVariable(name: "b", arg: 2, scope: !12, file: !3, line: 15, type: !15) + !19 = !DILocalVariable(name: "quux", scope: !12, file: !3, line: 23, type: !7) + !28 = !DILocation(line: 1, column: 1, scope: !12) + +... +--- +name: f +tracksRegLiveness: true +liveins: + - { reg: '$rdi', virtual-reg: '' } + - { reg: '$rsi', virtual-reg: '' } +frameInfo: + stackSize: 72 + offsetAdjustment: -72 + maxAlignment: 8 + adjustsStack: true + hasCalls: true + cvBytesOfCalleeSavedRegisters: 48 +fixedStack: + - { id: 0, type: spill-slot, offset: -56, size: 8, alignment: 8, stack-id: default, + callee-saved-register: '$rbx', callee-saved-restored: true, debug-info-variable: '', + debug-info-expression: '', debug-info-location: '' } + - { id: 1, type: spill-slot, offset: -48, size: 8, alignment: 16, stack-id: default, + callee-saved-register: '$r12', callee-saved-restored: true, debug-info-variable: '', + debug-info-expression: '', debug-info-location: '' } + - { id: 2, type: spill-slot, offset: -40, size: 8, alignment: 8, stack-id: default, + callee-saved-register: '$r13', callee-saved-restored: true, debug-info-variable: '', + debug-info-expression: '', debug-info-location: '' } + - { id: 3, type: spill-slot, offset: -32, size: 8, alignment: 16, stack-id: default, + callee-saved-register: '$r14', callee-saved-restored: true, debug-info-variable: '', + debug-info-expression: '', debug-info-location: '' } + - { id: 4, type: spill-slot, offset: -24, size: 8, alignment: 8, stack-id: default, + callee-saved-register: '$r15', callee-saved-restored: true, debug-info-variable: '', + debug-info-expression: '', debug-info-location: '' } + - { id: 5, type: spill-slot, offset: -16, size: 8, alignment: 16, stack-id: default, + callee-saved-register: '$rbp', callee-saved-restored: true, debug-info-variable: '', + debug-info-expression: '', debug-info-location: '' } +stack: + - { id: 0, name: '', type: spill-slot, offset: -72, size: 8, alignment: 8, + stack-id: default, callee-saved-register: '', callee-saved-restored: true, + debug-info-variable: '', debug-info-expression: '', debug-info-location: '' } + - { id: 1, name: '', type: spill-slot, offset: -64, size: 8, alignment: 8, + stack-id: default, callee-saved-register: '', callee-saved-restored: true, + debug-info-variable: '', debug-info-expression: '', debug-info-location: '' } +body: | + bb.0.entry: + successors: %bb.4, %bb.1 + liveins: $rdi, $rsi, $rbp, $r15, $r14, $r13, $r12, $rbx + + DBG_VALUE $rdi, $noreg, !17, !DIExpression(), debug-location !28 + DBG_VALUE $rdi, $noreg, !17, !DIExpression(), debug-location !28 + DBG_VALUE $rsi, $noreg, !18, !DIExpression(), debug-location !28 + DBG_VALUE $rsi, $noreg, !18, !DIExpression(), debug-location !28 + frame-setup PUSH64r killed $rbp, implicit-def $rsp, implicit $rsp, debug-location !28 + frame-setup PUSH64r killed $r15, implicit-def $rsp, implicit $rsp, debug-location !28 + frame-setup PUSH64r killed $r14, implicit-def $rsp, implicit $rsp, debug-location !28 + frame-setup PUSH64r killed $r13, implicit-def $rsp, implicit $rsp, debug-location !28 + frame-setup PUSH64r killed $r12, implicit-def $rsp, implicit $rsp, debug-location !28 + frame-setup PUSH64r killed $rbx, implicit-def $rsp, implicit $rsp, debug-location !28 + $rsp = frame-setup SUB64ri8 $rsp, 24, implicit-def dead $eflags + renamable $ecx = MOV32rm $rip, 1, $noreg, @bees, $noreg, debug-location !28 :: (volatile dereferenceable load 4 from @bees) + $eax = MOV32ri 3, implicit-def $rax + CMP32ri8 killed renamable $ecx, 12, implicit-def $eflags, debug-location !28 + JCC_1 %bb.4, 4, implicit $eflags, debug-location !28 + + bb.1.if.end: + successors: %bb.2, %bb.3 + liveins: $rdi, $rsi + + MOV64mr $rsp, 1, $noreg, 16, $noreg, killed renamable $rsi :: (store 8 into %stack.1) + MOV64mr $rsp, 1, $noreg, 8, $noreg, killed renamable $rdi :: (store 8 into %stack.0) + INLINEASM &"", 1, 12, implicit-def dead early-clobber $rax, 12, implicit-def dead early-clobber $rbx, 12, implicit-def dead early-clobber $rcx, 12, implicit-def dead early-clobber $rdx, 12, implicit-def dead early-clobber $rsi, 12, implicit-def dead early-clobber $rdi, 12, implicit-def dead early-clobber $rbp, 12, implicit-def dead early-clobber $r8, 12, implicit-def dead early-clobber $r9, 12, implicit-def dead early-clobber $r10, 12, implicit-def dead early-clobber $r11, 12, implicit-def dead early-clobber $r12, 12, implicit-def dead early-clobber $r13, 12, implicit-def dead early-clobber $r14, 12, implicit-def dead early-clobber $r15, 12, implicit-def dead early-clobber $df, 12, implicit-def dead early-clobber $fpsw, 12, implicit-def dead early-clobber $eflags, debug-location !28 + renamable $eax = MOV32rm $rip, 1, $noreg, @bees, $noreg, debug-location !28 :: (volatile dereferenceable load 4 from @bees) + CMP32ri8 killed renamable $eax, 2, implicit-def $eflags, debug-location !28 + JCC_1 %bb.3, 5, implicit killed $eflags, debug-location !28 + + bb.2.if.then2: + successors: %bb.4 + + renamable $rax = MOV64rm $rsp, 1, $noreg, 8, $noreg :: (load 8 from %stack.0) + renamable $rax = SUB64rm killed renamable $rax, $rsp, 1, $noreg, 16, $noreg, implicit-def dead $eflags, debug-location !28 :: (load 8 from %stack.1) + JMP_1 %bb.4 + + bb.3.if.end3: + successors: %bb.4 + + $edi = MOV32ri 1, implicit-def $rdi, debug-location !28 + $esi = MOV32ri 2, implicit-def $rsi, debug-location !28 + CALL64pcrel32 @sum, csr_64, implicit $rsp, implicit $ssp, implicit $rdi, implicit $rsi, implicit-def $rsp, implicit-def $ssp, implicit-def $rax, debug-location !28 + MOV64mr $rsp, 1, $noreg, 8, $noreg, $rax :: (store 8 into %stack.0) + INLINEASM &"", 1, 12, implicit-def dead early-clobber $rax, 12, implicit-def dead early-clobber $rbx, 12, implicit-def dead early-clobber $rcx, 12, implicit-def dead early-clobber $rdx, 12, implicit-def dead early-clobber $rsi, 12, implicit-def dead early-clobber $rdi, 12, implicit-def dead early-clobber $rbp, 12, implicit-def dead early-clobber $r8, 12, implicit-def dead early-clobber $r9, 12, implicit-def dead early-clobber $r10, 12, implicit-def dead early-clobber $r11, 12, implicit-def dead early-clobber $r12, 12, implicit-def dead early-clobber $r13, 12, implicit-def dead early-clobber $r14, 12, implicit-def dead early-clobber $r15, 12, implicit-def dead early-clobber $df, 12, implicit-def dead early-clobber $fpsw, 12, implicit-def dead early-clobber $eflags, debug-location !28 + ADD32mi8 $rip, 1, $noreg, @bees, $noreg, 1, implicit-def dead $eflags, debug-location !28 :: (volatile store 4 into @bees), (volatile dereferenceable load 4 from @bees) + renamable $rax = MOVSX64rm32 $rsp, 1, $noreg, 8, $noreg, debug-location !28 :: (load 4 from %stack.0, align 8) + + bb.4.return: + liveins: $rax + + $rsp = frame-destroy ADD64ri8 $rsp, 24, implicit-def dead $eflags, debug-location !28 + $rbx = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !28 + $r12 = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !28 + $r13 = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !28 + $r14 = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !28 + $r15 = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !28 + $rbp = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !28 + RETQ $rax, debug-location !28 + +...