[llvm] r369247 - [DebugInfo] Make postra sinking of DBG_VALUEs subregister-safe
Jeremy Morse via llvm-commits
llvm-commits at lists.llvm.org
Mon Aug 19 02:53:07 PDT 2019
Author: jmorse
Date: Mon Aug 19 02:53:07 2019
New Revision: 369247
URL: http://llvm.org/viewvc/llvm-project?rev=369247&view=rev
Log:
[DebugInfo] Make postra sinking of DBG_VALUEs subregister-safe
Currently the machine instruction sinker identifies DBG_VALUE insts that
also need to sink by comparing register numbers. Unfortunately this isn't
safe, because (after register allocation) a DBG_VALUE may read a register
that aliases what's being sunk. To fix this, identify the DBG_VALUEs that
need to sink by recording & examining their register units. Register units
gives us the following guarantee:
"Two registers overlap if and only if they have a common register unit"
[MCRegisterInfo.h]
Thus we can always identify aliasing DBG_VALUEs if the set of register
units read by the DBG_VALUE, and the register units of the instruction
being sunk, intersect. (MachineSink already uses classes like
"LiveRegUnits" for determining sinking validity anyway).
The test added checks for super and subregister DBG_VALUE reads of a sunk
copy being sunk as well.
Differential Revision: https://reviews.llvm.org/D58191
Added:
llvm/trunk/test/DebugInfo/MIR/X86/postra-subreg-sink.mir
Modified:
llvm/trunk/lib/CodeGen/MachineSink.cpp
Modified: llvm/trunk/lib/CodeGen/MachineSink.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineSink.cpp?rev=369247&r1=369246&r2=369247&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineSink.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineSink.cpp Mon Aug 19 02:53:07 2019
@@ -36,8 +36,9 @@
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/BasicBlock.h"
-#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/DebugInfoMetadata.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Pass.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/CommandLine.h"
@@ -957,8 +958,9 @@ private:
/// Track which register units have been modified and used.
LiveRegUnits ModifiedRegUnits, UsedRegUnits;
- /// Track DBG_VALUEs of (unmodified) register units.
- DenseMap<unsigned, TinyPtrVector<MachineInstr*>> SeenDbgInstrs;
+ /// Track DBG_VALUEs of (unmodified) register units. Each DBG_VALUE has an
+ /// entry in this map for each unit it touches.
+ DenseMap<unsigned, TinyPtrVector<MachineInstr *>> SeenDbgInstrs;
/// Sink Copy instructions unused in the same block close to their uses in
/// successors.
@@ -1093,6 +1095,14 @@ static bool hasRegisterDependency(Machin
return HasRegDependency;
}
+static SmallSet<unsigned, 4> getRegUnits(unsigned Reg,
+ const TargetRegisterInfo *TRI) {
+ SmallSet<unsigned, 4> RegUnits;
+ for (auto RI = MCRegUnitIterator(Reg, TRI); RI.isValid(); ++RI)
+ RegUnits.insert(*RI);
+ return RegUnits;
+}
+
bool PostRAMachineSinking::tryToSinkCopy(MachineBasicBlock &CurBB,
MachineFunction &MF,
const TargetRegisterInfo *TRI,
@@ -1136,8 +1146,10 @@ bool PostRAMachineSinking::tryToSinkCopy
ModifiedRegUnits, UsedRegUnits))
continue;
- // Record debug use of this register.
- SeenDbgInstrs[MO.getReg()].push_back(MI);
+ // Record debug use of each reg unit.
+ SmallSet<unsigned, 4> Units = getRegUnits(MO.getReg(), TRI);
+ for (unsigned Reg : Units)
+ SeenDbgInstrs[Reg].push_back(MI);
}
continue;
}
@@ -1176,15 +1188,22 @@ bool PostRAMachineSinking::tryToSinkCopy
assert((SuccBB->pred_size() == 1 && *SuccBB->pred_begin() == &CurBB) &&
"Unexpected predecessor");
- // Collect DBG_VALUEs that must sink with this copy.
+ // Collect DBG_VALUEs that must sink with this copy. We've previously
+ // recorded which reg units that DBG_VALUEs read, if this instruction
+ // writes any of those units then the corresponding DBG_VALUEs must sink.
+ SetVector<MachineInstr *> DbgValsToSinkSet;
SmallVector<MachineInstr *, 4> DbgValsToSink;
for (auto &MO : MI->operands()) {
if (!MO.isReg() || !MO.isDef())
continue;
- Register reg = MO.getReg();
- for (auto *MI : SeenDbgInstrs.lookup(reg))
- DbgValsToSink.push_back(MI);
+
+ SmallSet<unsigned, 4> Units = getRegUnits(MO.getReg(), TRI);
+ for (unsigned Reg : Units)
+ for (auto *MI : SeenDbgInstrs.lookup(Reg))
+ DbgValsToSinkSet.insert(MI);
}
+ DbgValsToSink.insert(DbgValsToSink.begin(), DbgValsToSinkSet.begin(),
+ DbgValsToSinkSet.end());
// Clear the kill flag if SrcReg is killed between MI and the end of the
// block.
Added: llvm/trunk/test/DebugInfo/MIR/X86/postra-subreg-sink.mir
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/MIR/X86/postra-subreg-sink.mir?rev=369247&view=auto
==============================================================================
--- llvm/trunk/test/DebugInfo/MIR/X86/postra-subreg-sink.mir (added)
+++ llvm/trunk/test/DebugInfo/MIR/X86/postra-subreg-sink.mir Mon Aug 19 02:53:07 2019
@@ -0,0 +1,104 @@
+# RUN: llc -mtriple=x86_64-unknown-unknown %s -run-pass=postra-machine-sink -o - | FileCheck %s
+# Test that when we run the postra machine sinker (which sinks COPYs), that
+# DBG_VALUEs of both sub and super-registers that depend on such COPYs are
+# sunk with them.
+--- |
+ ; Module stripped of everything, MIR below is what's interesting
+ ; ModuleID = '<stdin>'
+ source_filename = "justacall.cpp"
+ target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+ target triple = "x86_64-unknown-linux-gnu"
+
+ ; Function Attrs: noinline norecurse nounwind uwtable
+ define dso_local i32 @main(i32 %argc, i8** nocapture readnone %argv) !dbg !14 {
+ entry:
+ br label %return
+ return:
+ ret i32 0
+ }
+
+ !llvm.dbg.cu = !{!2}
+ !llvm.module.flags = !{!1, !1000}
+
+ !0 = !{!"dummy metadata"}
+ !1 = !{i32 2, !"Dwarf Version", i32 4}
+ !1000 = !{i32 2, !"Debug Info Version", i32 3}
+ !2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, nameTableKind: None)
+ !3 = !DIFile(filename: "justacall.cpp", directory: "/tmp")
+ !4 = !{}
+ !7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+ !8 = !DIBasicType(name: "int", size: 8, encoding: DW_ATE_signed)
+ !9 = !DIBasicType(name: "int", size: 16, encoding: DW_ATE_signed)
+ !14 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 7, type: !15, isLocal: false, isDefinition: true, scopeLine: 8, flags: DIFlagPrototyped, isOptimized: true, unit: !2, retainedNodes: !20)
+ !15 = !DISubroutineType(types: !16)
+ !16 = !{!7, !7}
+ !20 = !{!21, !22, !23, !24}
+ !21 = !DILocalVariable(name: "argc", arg: 1, scope: !14, file: !3, line: 7, type: !7)
+ !22 = !DILocalVariable(name: "foo", scope: !14, file: !3, line: 7, type: !8)
+ !23 = !DILocalVariable(name: "bar", scope: !14, file: !3, line: 7, type: !7)
+ !24 = !DILocalVariable(name: "baz", scope: !14, file: !3, line: 7, type: !9)
+ !100 = !DILocation(line: 1, scope: !14)
+
+...
+---
+name: main
+tracksRegLiveness: true
+registers:
+liveins:
+ - { reg: '$edi', virtual-reg: '' }
+frameInfo:
+ hasCalls: true
+fixedStack:
+stack:
+constants:
+body: |
+
+ ; CHECK: ![[ARGVAR:[0-9]+]] = !DILocalVariable(name: "argc",
+ ; CHECK: ![[FOOVAR:[0-9]+]] = !DILocalVariable(name: "foo",
+ ; CHECK: ![[BARVAR:[0-9]+]] = !DILocalVariable(name: "bar",
+ ; CHECK: ![[BAZVAR:[0-9]+]] = !DILocalVariable(name: "baz",
+
+ ; In the following code, the:
+ ; DBG_VALUE of $edi should not sink: it's an argument
+ ; DBG_VALUE of $ebx should sink: it's a standard copy
+ ; DBG_VALUE of $bx should sink: a write of its superregister sinks
+ ; DBG_VALUE of $ecx should sink: a write of one of its subregisters sinks
+
+ ; CHECK-LABEL: name: main
+ ; CHECK: bb.0.entry:
+ ; CHECK: successors: %bb.1(0x80000000)
+ ; CHECK: liveins: $edi
+ ; CHECK: DBG_VALUE $edi, $noreg, ![[BARVAR]]
+ ; CHECK-NEXT: renamable $cl = MOV8ri 1
+ ; CHECK-NEXT: JMP_1 %bb.1
+ ; CHECK: bb.1.return:
+ ; CHECK: liveins: $cl, $edi
+ ; CHECK: renamable $ebx = COPY $edi
+ ; CHECK-NEXT: DBG_VALUE $bx, $noreg, ![[BAZVAR]]
+ ; CHECK-NEXT: DBG_VALUE $ebx, $noreg, ![[ARGVAR]]
+ ; CHECK-NEXT: renamable $ch = COPY renamable $cl
+ ; CHECK-NEXT: DBG_VALUE $ecx, $noreg, ![[FOOVAR]]
+ ; CHECK-NEXT: $rdi = MOV32ri64 0
+ ; CHECK-NEXT: $eax = MOV32r0 implicit-def dead $eflags
+ ; CHECK-NEXT: RET 0, $eax
+ bb.0.entry:
+ successors: %bb.1(0x40000000)
+ liveins: $edi
+
+ DBG_VALUE $edi, $noreg, !23, !DIExpression(), debug-location !100
+ renamable $ebx = COPY $edi
+ DBG_VALUE $ebx, $noreg, !21, !DIExpression(), debug-location !100
+ DBG_VALUE $bx, $noreg, !24, !DIExpression(), debug-location !100
+ renamable $cl = MOV8ri 1, debug-location !100
+ renamable $ch = COPY renamable $cl
+ DBG_VALUE $ecx, $noreg, !22, !DIExpression(), debug-location !100
+ JMP_1 %bb.1
+
+ bb.1.return:
+ liveins: $ebx, $ch
+
+ $rdi = MOV32ri64 0
+ $eax = MOV32r0 implicit-def dead $eflags
+ RET 0, $eax
+
+...
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