[llvm] fca4100 - [DebugInfo] Re-apply two patches to MachineSink

Jeremy Morse via llvm-commits llvm-commits at lists.llvm.org
Thu Dec 5 07:54:42 PST 2019


Author: Jeremy Morse
Date: 2019-12-05T15:52:20Z
New Revision: fca41001963cb473182c7b3b665ea1f03f94203a

URL: https://github.com/llvm/llvm-project/commit/fca41001963cb473182c7b3b665ea1f03f94203a
DIFF: https://github.com/llvm/llvm-project/commit/fca41001963cb473182c7b3b665ea1f03f94203a.diff

LOG: [DebugInfo] Re-apply two patches to MachineSink

These were:
 * D58386 / f5e1b718a67 / reverted in d382a8a768b
 * D58238 / ee50590e168 / reverted in a8db456b53a

Of which the latter has a performance regression tracked in PR43855,
fixed by D70672 / D70676, which will be committed atomically with this
reapplication.

Contains a minor difference to account for a change in the IsCopyInstr
signature.

Added: 
    llvm/test/DebugInfo/MIR/X86/machinesink.mir
    llvm/test/DebugInfo/MIR/X86/sink-leaves-undef.mir

Modified: 
    llvm/lib/CodeGen/MachineSink.cpp
    llvm/test/DebugInfo/MIR/X86/postra-subreg-sink.mir

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index 1b5fc2727fa7..f34e820a2e04 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -106,6 +106,9 @@ namespace {
     using AllSuccsCache =
         std::map<MachineBasicBlock *, SmallVector<MachineBasicBlock *, 4>>;
 
+    // Remember debug uses of vregs seen, so we know what to sink out of blocks.
+    DenseMap<unsigned, TinyPtrVector<MachineInstr *>> SeenDbgUsers;
+
   public:
     static char ID; // Pass identification
 
@@ -133,6 +136,7 @@ namespace {
 
   private:
     bool ProcessBlock(MachineBasicBlock &MBB);
+    void ProcessDbgInst(MachineInstr &MI);
     bool isWorthBreakingCriticalEdge(MachineInstr &MI,
                                      MachineBasicBlock *From,
                                      MachineBasicBlock *To);
@@ -154,8 +158,14 @@ namespace {
                                    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;
@@ -368,8 +378,11 @@ bool MachineSinking::ProcessBlock(MachineBasicBlock &MBB) {
     if (!ProcessedBegin)
       --I;
 
-    if (MI.isDebugInstr())
+    if (MI.isDebugInstr()) {
+      if (MI.isDebugValue())
+        ProcessDbgInst(MI);
       continue;
+    }
 
     bool Joined = PerformTrivialForwardCoalescing(MI, &MBB);
     if (Joined) {
@@ -385,9 +398,23 @@ bool MachineSinking::ProcessBlock(MachineBasicBlock &MBB) {
     // 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) {
@@ -732,18 +759,12 @@ static bool SinkingPreventsImplicitNullCheck(MachineInstr &MI,
          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<MachineInstr *> *DbgVals = nullptr) {
-  // If debug values are provided use those, otherwise call collectDebugValues.
-  SmallVector<MachineInstr *, 2> DbgValuesToSink;
-  if (DbgVals)
-    DbgValuesToSink.insert(DbgValuesToSink.begin(),
-                           DbgVals->begin(), DbgVals->end());
-  else
-    MI.collectDebugValues(DbgValuesToSink);
+                        SmallVectorImpl<MachineInstr *> &DbgValuesToSink) {
+  const MachineRegisterInfo &MRI = MI.getMF()->getRegInfo();
+  const TargetInstrInfo &TII = *MI.getMF()->getSubtarget().getInstrInfo();
 
   // 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
@@ -759,13 +780,60 @@ static void performSink(MachineInstr &MI, MachineBasicBlock &SuccToSinkTo,
   SuccToSinkTo.splice(InsertPos, ParentBlock, MI,
                       ++MachineBasicBlock::iterator(MI));
 
-  // Move previously adjacent debug value instructions to the insert position.
+  // Sink a copy of debug users to the insert position. Mark the original
+  // DBG_VALUE location as 'undef', indicating that any earlier variable
+  // location should be terminated as we've optimised away the value at this
+  // point.
+  // If the sunk instruction is a copy, try to forward the copy instead of
+  // leaving an 'undef' DBG_VALUE in the original location. Don't do this if
+  // there's any subregister weirdness involved.
   for (SmallVectorImpl<MachineInstr *>::iterator DBI = DbgValuesToSink.begin(),
                                                  DBE = DbgValuesToSink.end();
        DBI != DBE; ++DBI) {
     MachineInstr *DbgMI = *DBI;
-    SuccToSinkTo.splice(InsertPos, ParentBlock, DbgMI,
-                        ++MachineBasicBlock::iterator(DbgMI));
+    MachineInstr *NewDbgMI = DbgMI->getMF()->CloneMachineInstr(*DBI);
+    SuccToSinkTo.insert(InsertPos, NewDbgMI);
+
+    // Copy DBG_VALUE operand and set the original to undef. We then check to
+    // see whether this is something that can be copy-forwarded. If it isn't,
+    // continue around the loop.
+    MachineOperand DbgMO = DbgMI->getOperand(0);
+    DbgMI->getOperand(0).setReg(0);
+
+    const MachineOperand *SrcMO = nullptr, *DstMO = nullptr;
+    auto CopyOperands = TII.isCopyInstr(MI);
+    if (!CopyOperands)
+      continue;
+    SrcMO = CopyOperands->Source;
+    DstMO = CopyOperands->Destination;
+
+    // Check validity of forwarding this copy.
+    bool PostRA = MRI.getNumVirtRegs() == 0;
+
+    // Trying to forward between physical and virtual registers is too hard.
+    if (DbgMO.getReg().isVirtual() != SrcMO->getReg().isVirtual())
+      continue;
+
+    // Only try virtual register copy-forwarding before regalloc, and physical
+    // register copy-forwarding after regalloc.
+    bool arePhysRegs = !DbgMO.getReg().isVirtual();
+    if (arePhysRegs != PostRA)
+      continue;
+
+    // Pre-regalloc, only forward if all subregisters agree (or there are no
+    // subregs at all). More analysis might recover some forwardable copies.
+    if (!PostRA && (DbgMO.getSubReg() != SrcMO->getSubReg() ||
+                    DbgMO.getSubReg() != DstMO->getSubReg()))
+      continue;
+
+    // Post-regalloc, we may be sinking a DBG_VALUE of a sub or super-register
+    // of this copy. Only forward the copy if the DBG_VALUE operand exactly
+    // matches the copy destination.
+    if (PostRA && DbgMO.getReg() != DstMO->getReg())
+      continue;
+
+    DbgMI->getOperand(0).setReg(SrcMO->getReg());
+    DbgMI->getOperand(0).setSubReg(SrcMO->getSubReg());
   }
 }
 
@@ -883,7 +951,25 @@ bool MachineSinking::SinkInstruction(MachineInstr &MI, bool &SawStore,
   while (InsertPos != SuccToSinkTo->end() && InsertPos->isPHI())
     ++InsertPos;
 
-  performSink(MI, *SuccToSinkTo, InsertPos);
+  // Collect debug users of any vreg that this inst defines.
+  SmallVector<MachineInstr *, 4> 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.
@@ -898,6 +984,41 @@ bool MachineSinking::SinkInstruction(MachineInstr &MI, bool &SawStore,
   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<MachineInstr *, 4> 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
@@ -1207,7 +1328,7 @@ bool PostRAMachineSinking::tryToSinkCopy(MachineBasicBlock &CurBB,
     // 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
index 000000000000..3df80ee15f51
--- /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 
diff erent 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
+...

diff  --git a/llvm/test/DebugInfo/MIR/X86/postra-subreg-sink.mir b/llvm/test/DebugInfo/MIR/X86/postra-subreg-sink.mir
index 01e81ea39f9a..8cca1de12b9b 100644
--- a/llvm/test/DebugInfo/MIR/X86/postra-subreg-sink.mir
+++ b/llvm/test/DebugInfo/MIR/X86/postra-subreg-sink.mir
@@ -69,7 +69,10 @@ body:             |
   ; CHECK:   successors: %bb.1(0x80000000)
   ; CHECK:   liveins: $edi
   ; CHECK:   DBG_VALUE $edi, $noreg, ![[BARVAR]]
+  ; CHECK-NEXT:   DBG_VALUE $edi, $noreg, ![[ARGVAR]]
+  ; CHECK-NEXT:   DBG_VALUE $noreg, $noreg, ![[BAZVAR]]
   ; CHECK-NEXT:   renamable $cl = MOV8ri 1
+  ; CHECK-NEXT:   DBG_VALUE $noreg, $noreg, ![[FOOVAR]]
   ; CHECK-NEXT:   JMP_1 %bb.1
   ; CHECK: bb.1.return:
   ; CHECK:   liveins: $cl, $edi

diff  --git a/llvm/test/DebugInfo/MIR/X86/sink-leaves-undef.mir b/llvm/test/DebugInfo/MIR/X86/sink-leaves-undef.mir
new file mode 100644
index 000000000000..21668fc89f6b
--- /dev/null
+++ b/llvm/test/DebugInfo/MIR/X86/sink-leaves-undef.mir
@@ -0,0 +1,105 @@
+# RUN: llc %s -o - -run-pass=machine-sink -mtriple=x86_64-- | FileCheck %s
+# This is a copy of test/CodeGen/X86/MachineSink-DbgValue.ll, where we
+# additionally test that when the MOV32rm defining %0 is sunk, it leaves
+# an 'undef' DBG_VALUE behind to terminate earlier location ranges.
+--- |
+  target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+  target triple = "x86_64-apple-macosx10.7.0"
+  
+  ; Function Attrs: nounwind readonly ssp uwtable
+  define i32 @foo(i32 %i, i32* nocapture %c) !dbg !4 {
+    call void @llvm.dbg.value(metadata i32 %i, metadata !9, metadata !DIExpression()), !dbg !14
+    %ab = load i32, i32* %c, align 1, !dbg !15
+    call void @llvm.dbg.value(metadata i32* %c, metadata !10, metadata !DIExpression()), !dbg !16
+    call void @llvm.dbg.value(metadata i32 %ab, metadata !12, metadata !DIExpression()), !dbg !15
+    %cd = icmp eq i32 %i, 42, !dbg !17
+    br i1 %cd, label %bb1, label %bb2, !dbg !17
+  
+  bb1:                                              ; preds = %0
+    %gh = add nsw i32 %ab, 2, !dbg !18
+    br label %bb2, !dbg !18
+  
+  bb2:                                              ; preds = %bb1, %0
+    %.0 = phi i32 [ %gh, %bb1 ], [ 0, %0 ]
+    ret i32 %.0, !dbg !19
+  }
+  
+  ; Function Attrs: nounwind readnone speculatable
+  declare void @llvm.dbg.value(metadata, metadata, metadata)
+  
+  ; Function Attrs: nounwind
+  declare void @llvm.stackprotector(i8*, i8**)
+  
+  !llvm.dbg.cu = !{!0}
+  !llvm.module.flags = !{!3}
+  
+  !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "Apple clang version 3.0 (tags/Apple/clang-211.10.1) (based on LLVM 3.0svn)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !2)
+  !1 = !DIFile(filename: "a.c", directory: "/private/tmp")
+  !2 = !{}
+  !3 = !{i32 1, !"Debug Info Version", i32 3}
+  !4 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 2, type: !5, virtualIndex: 6, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
+  !5 = !DISubroutineType(types: !6)
+  !6 = !{!7}
+  !7 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+  !8 = !{!9, !10, !12}
+  !9 = !DILocalVariable(name: "i", arg: 1, scope: !4, file: !1, line: 2, type: !7)
+  !10 = !DILocalVariable(name: "c", arg: 2, scope: !4, file: !1, line: 2, type: !11)
+  !11 = !DIDerivedType(tag: DW_TAG_pointer_type, scope: !0, baseType: !7, size: 64, align: 64)
+  !12 = !DILocalVariable(name: "a", scope: !13, file: !1, line: 3, type: !7)
+  !13 = distinct !DILexicalBlock(scope: !4, file: !1, line: 2, column: 25)
+  !14 = !DILocation(line: 2, column: 13, scope: !4)
+  !15 = !DILocation(line: 3, column: 14, scope: !13)
+  !16 = !DILocation(line: 2, column: 22, scope: !4)
+  !17 = !DILocation(line: 4, column: 3, scope: !13)
+  !18 = !DILocation(line: 5, column: 5, scope: !13)
+  !19 = !DILocation(line: 7, column: 1, scope: !13)
+  ; CHECK: ![[VARNUM:[0-9]+]] = !DILocalVariable(name: "a",
+...
+---
+name:            foo
+alignment:       4
+tracksRegLiveness: true
+registers:       
+  - { id: 0, class: gr32 }
+  - { id: 1, class: gr32 }
+  - { id: 2, class: gr32 }
+  - { id: 3, class: gr32 }
+  - { id: 4, class: gr64 }
+  - { id: 5, class: gr32 }
+  - { id: 6, class: gr32 }
+liveins:         
+  - { reg: '$edi', virtual-reg: '%3' }
+  - { reg: '$rsi', virtual-reg: '%4' }
+body:             |
+  bb.0 (%ir-block.0):
+    successors: %bb.1, %bb.2
+    liveins: $edi, $rsi
+  ; CHECK-LABEL: bb.0 (%ir-block.0):
+  ; CHECK:       DBG_VALUE $noreg, $noreg, ![[VARNUM]]
+  
+    DBG_VALUE $edi, $noreg, !9, !DIExpression(), debug-location !14
+    DBG_VALUE $rsi, $noreg, !10, !DIExpression(), debug-location !16
+    %4:gr64 = COPY $rsi
+    DBG_VALUE %4, $noreg, !10, !DIExpression(), debug-location !16
+    %3:gr32 = COPY $edi
+    DBG_VALUE %3, $noreg, !9, !DIExpression(), debug-location !14
+    %0:gr32 = MOV32rm %4, 1, $noreg, 0, $noreg, debug-location !15 :: (load 4 from %ir.c, align 1)
+    DBG_VALUE %0, $noreg, !12, !DIExpression(), debug-location !15
+    %5:gr32 = MOV32r0 implicit-def dead $eflags
+    %6:gr32 = SUB32ri8 %3, 42, implicit-def $eflags, debug-location !17
+    JCC_1 %bb.2, 5, implicit $eflags, debug-location !17
+    JMP_1 %bb.1, debug-location !17
+  
+  bb.1.bb1:
+  ; CHECK-LABEL: bb.1.bb1:
+  ; CHECK:       %[[VREG:[0-9]+]]:gr32 = MOV32rm
+  ; CHECK-NEXT:  DBG_VALUE %[[VREG]], $noreg, ![[VARNUM]]
+  ; CHECK-NEXT:  ADD32ri8
+    %1:gr32 = nsw ADD32ri8 %0, 2, implicit-def dead $eflags, debug-location !18
+  
+  bb.2.bb2:
+    %2:gr32 = PHI %5, %bb.0, %1, %bb.1
+    $eax = COPY %2, debug-location !19
+    RET 0, $eax, debug-location !19
+
+...


        


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