}
};
- 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<VarLoc::SpillLoc> isRestoreInstruction(const MachineInstr &MI,
}
}
-/// 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<const MachineMemOperand*, 1> Accesses;
-
+ MachineFunction *MF) {
// TODO: Handle multiple stores folded into one.
if (!MI.hasOneMemOperand())
return false;
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;
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)
--- /dev/null
+# 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
+
+...