Use the frame index side table for byval and inalloca arguments

rnk · rnk · commit 45efcf0c9608 · 2017-05-08T23:20:27.000Z
Summary: For inalloca functions, this is a very common code pattern: %argpack = type <{ i32, i32, i32 }> define void @f(%argpack* inalloca %args) { entry: %a = getelementptr inbounds %argpack, %argpack* %args, i32 0, i32 0 %b = getelementptr inbounds %argpack, %argpack* %args, i32 0, i32 1 %c = getelementptr inbounds %argpack, %argpack* %args, i32 0, i32 2 tail call void @llvm.dbg.declare(metadata i32* %a, ... "a") tail call void @llvm.dbg.declare(metadata i32* %c, ... "b") tail call void @llvm.dbg.declare(metadata i32* %b, ... "c") Even though these GEPs can be simplified to a constant offset from EBP or RSP, we don't do that at -O0, and each GEP is computed into a register. Registers used to compute argument addresses are typically spilled and clobbered very quickly after the initial computation, so live debug variable tracking loses information very quickly if we use DBG_VALUE instructions. This change moves processing of dbg.declare between argument lowering and basic block isel, so that we can ask if an argument has a frame index or not. If the argument lives in a register as is the case for byval arguments on some targets, then we don't put it in the side table and during ISel we emit DBG_VALUE instructions. Reviewers: aprantl Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D32980 llvm-svn: 302483
diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -1150,16 +1150,16 @@ bool FastISel::selectIntrinsicCall(const IntrinsicInst *II) {
       return true;
     }
 
-    unsigned Offset = 0;
+    // Byval arguments with frame indices were already handled after argument
+    // lowering and before isel.
+    const auto *Arg =
+        dyn_cast<Argument>(Address->stripInBoundsConstantOffsets());
+    if (Arg && FuncInfo.getArgumentFrameIndex(Arg) != INT_MAX)
+      return true;
+
     Optional<MachineOperand> Op;
-    if (const auto *Arg = dyn_cast<Argument>(Address))
-      // Some arguments' frame index is recorded during argument lowering.
-      Offset = FuncInfo.getArgumentFrameIndex(Arg);
-    if (Offset)
-      Op = MachineOperand::CreateFI(Offset);
-    if (!Op)
-      if (unsigned Reg = lookUpRegForValue(Address))
-        Op = MachineOperand::CreateReg(Reg, false);
+    if (unsigned Reg = lookUpRegForValue(Address))
+      Op = MachineOperand::CreateReg(Reg, false);
 
     // If we have a VLA that has a "use" in a metadata node that's then used
     // here but it has no other uses, then we have a problem. E.g.,
diff --git a/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp b/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
@@ -85,7 +85,6 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
   MF = &mf;
   TLI = MF->getSubtarget().getTargetLowering();
   RegInfo = &MF->getRegInfo();
-  MachineModuleInfo &MMI = MF->getMMI();
   const TargetFrameLowering *TFI = MF->getSubtarget().getFrameLowering();
   unsigned StackAlign = TFI->getStackAlignment();
 
@@ -214,33 +213,6 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
         if (!isa<AllocaInst>(I) || !StaticAllocaMap.count(cast<AllocaInst>(&I)))
           InitializeRegForValue(&I);
 
-      // Collect llvm.dbg.declare information. This is done now instead of
-      // during the initial isel pass through the IR so that it is done
-      // in a predictable order.
-      if (const DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(&I)) {
-        assert(DI->getVariable() && "Missing variable");
-        assert(DI->getDebugLoc() && "Missing location");
-        if (MMI.hasDebugInfo()) {
-          // Don't handle byval struct arguments or VLAs, for example.
-          // Non-byval arguments are handled here (they refer to the stack
-          // temporary alloca at this point).
-          const Value *Address = DI->getAddress();
-          if (Address) {
-            if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Address))
-              Address = BCI->getOperand(0);
-            if (const AllocaInst *AI = dyn_cast<AllocaInst>(Address)) {
-              DenseMap<const AllocaInst *, int>::iterator SI =
-                StaticAllocaMap.find(AI);
-              if (SI != StaticAllocaMap.end()) { // Check for VLAs.
-                int FI = SI->second;
-                MF->setVariableDbgInfo(DI->getVariable(), DI->getExpression(),
-                                       FI, DI->getDebugLoc());
-              }
-            }
-          }
-        }
-      }
-
       // Decide the preferred extend type for a value.
       PreferredExtendType[&I] = getPreferredExtendForValue(&I);
     }
@@ -510,12 +482,11 @@ void FunctionLoweringInfo::setArgumentFrameIndex(const Argument *A,
 /// If the argument does not have any assigned frame index then 0 is
 /// returned.
 int FunctionLoweringInfo::getArgumentFrameIndex(const Argument *A) {
-  DenseMap<const Argument *, int>::iterator I =
-    ByValArgFrameIndexMap.find(A);
+  auto I = ByValArgFrameIndexMap.find(A);
   if (I != ByValArgFrameIndexMap.end())
     return I->second;
   DEBUG(dbgs() << "Argument does not have assigned frame index!\n");
-  return 0;
+  return INT_MAX;
 }
 
 unsigned FunctionLoweringInfo::getCatchPadExceptionPointerVReg(
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4676,7 +4676,8 @@ bool SelectionDAGBuilder::EmitFuncArgumentDbgValue(
   bool IsIndirect = false;
   Optional<MachineOperand> Op;
   // Some arguments' frame index is recorded during argument lowering.
-  if (int FI = FuncInfo.getArgumentFrameIndex(Arg))
+  int FI = FuncInfo.getArgumentFrameIndex(Arg);
+  if (FI != INT_MAX)
     Op = MachineOperand::CreateFI(FI);
 
   if (!Op && N.getNode()) {
@@ -4927,6 +4928,13 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
       return nullptr;
     }
 
+    // Byval arguments with frame indices were already handled after argument
+    // lowering and before isel.
+    const auto *Arg =
+        dyn_cast<Argument>(Address->stripInBoundsConstantOffsets());
+    if (Arg && FuncInfo.getArgumentFrameIndex(Arg) != INT_MAX)
+      return nullptr;
+
     SDValue &N = NodeMap[Address];
     if (!N.getNode() && isa<Argument>(Address))
       // Check unused arguments map.
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -38,6 +38,7 @@
 #include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineMemOperand.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachineOperand.h"
 #include "llvm/CodeGen/MachinePassRegistry.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
@@ -1145,6 +1146,51 @@ static void createSwiftErrorEntriesInEntryBlock(FunctionLoweringInfo *FuncInfo,
   }
 }
 
+/// Collect llvm.dbg.declare information. This is done after argument lowering
+/// in case the declarations refer to arguments.
+static void processDbgDeclares(FunctionLoweringInfo *FuncInfo) {
+  MachineFunction *MF = FuncInfo->MF;
+  const DataLayout &DL = MF->getDataLayout();
+  for (const BasicBlock &BB : *FuncInfo->Fn) {
+    for (const Instruction &I : BB) {
+      const DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(&I);
+      if (!DI)
+        continue;
+
+      assert(DI->getVariable() && "Missing variable");
+      assert(DI->getDebugLoc() && "Missing location");
+      const Value *Address = DI->getAddress();
+      if (!Address)
+        continue;
+
+      // Look through casts and constant offset GEPs. These mostly come from
+      // inalloca.
+      APInt Offset(DL.getPointerSizeInBits(0), 0);
+      Address = Address->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
+
+      // Check if the variable is a static alloca or a byval or inalloca
+      // argument passed in memory. If it is not, then we will ignore this
+      // intrinsic and handle this during isel like dbg.value.
+      int FI = INT_MAX;
+      if (const auto *AI = dyn_cast<AllocaInst>(Address)) {
+        auto SI = FuncInfo->StaticAllocaMap.find(AI);
+        if (SI != FuncInfo->StaticAllocaMap.end())
+          FI = SI->second;
+      } else if (const auto *Arg = dyn_cast<Argument>(Address))
+        FI = FuncInfo->getArgumentFrameIndex(Arg);
+
+      if (FI == INT_MAX)
+        continue;
+
+      DIExpression *Expr = DI->getExpression();
+      if (Offset.getBoolValue())
+        Expr = DIExpression::prepend(Expr, DIExpression::NoDeref,
+                                     Offset.getZExtValue());
+      MF->setVariableDbgInfo(DI->getVariable(), Expr, FI, DI->getDebugLoc());
+    }
+  }
+}
+
 /// Propagate swifterror values through the machine function CFG.
 static void propagateSwiftErrorVRegs(FunctionLoweringInfo *FuncInfo) {
   auto *TLI = FuncInfo->TLI;
@@ -1317,6 +1363,8 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) {
   }
   createSwiftErrorEntriesInEntryBlock(FuncInfo, FastIS, TLI, TII, SDB);
 
+  processDbgDeclares(FuncInfo);
+
   // Iterate over all basic blocks in the function.
   for (const BasicBlock *LLVMBB : RPOT) {
     if (OptLevel != CodeGenOpt::None) {
diff --git a/llvm/test/CodeGen/X86/2010-01-18-DbgValue.ll b/llvm/test/CodeGen/X86/2010-01-18-DbgValue.ll
@@ -1,14 +1,18 @@
-; RUN: llc -march=x86 -O0 < %s | FileCheck %s
-; Currently, dbg.declare generates a DEBUG_VALUE comment.  Eventually it will
-; generate DWARF and this test will need to be modified or removed.
+; RUN: llc -march=x86 -O0 < %s -filetype=obj | llvm-dwarfdump - | FileCheck %s
 
+; CHECK-LABEL: .debug_info contents:
+
+; CHECK-LABEL: DW_TAG_subprogram
+; CHECK:   DW_AT_name [DW_FORM_strp]       ( {{.*}}"foo")
+; CHECK:   DW_TAG_formal_parameter
+; CHECK-NEXT:     DW_AT_location [DW_FORM_exprloc]      (<0x2> 91 08 )
+; CHECK-NEXT:     DW_AT_name [DW_FORM_strp]     ( {{.*}}"my_r0")
 
 %struct.Pt = type { double, double }
 %struct.Rect = type { %struct.Pt, %struct.Pt }
 
 define double @foo(%struct.Rect* byval %my_r0) nounwind ssp !dbg !1 {
 entry:
-;CHECK: DEBUG_VALUE
   %retval = alloca double                         ; <double*> [#uses=2]
   %0 = alloca double                              ; <double*> [#uses=2]
   %"alloca point" = bitcast i32 0 to i32          ; <i32> [#uses=0]
diff --git a/llvm/test/CodeGen/X86/2012-11-30-handlemove-dbg.ll b/llvm/test/CodeGen/X86/2012-11-30-handlemove-dbg.ll
diff --git a/llvm/test/CodeGen/X86/dbg-baseptr.ll b/llvm/test/CodeGen/X86/dbg-baseptr.ll
@@ -1,4 +1,5 @@
 ; RUN: llc -o - %s | FileCheck %s
+; RUN: llc -filetype=obj -o - %s | llvm-dwarfdump - | FileCheck %s --check-prefix=DWARF
 ; This test checks that parameters on the stack pointer are correctly
 ; referenced by debug info.
 target triple = "x86_64--"
@@ -7,24 +8,54 @@ target triple = "x86_64--"
 @ptr = external global i32*
 %struct.s = type { i32, i32, i32, i32, i32 }
 
+; Simple case: no FP, use offset from RSP.
+
 ; CHECK-LABEL: f0:
-; CHECK: DEBUG_VALUE: f:input <- [%RSP+8]
+; CHECK-NOT: pushq
+; CHECK: movl $42, %eax
+; CHECK: retq
 define i32 @f0(%struct.s* byval align 8 %input) !dbg !8 {
   call void @llvm.dbg.declare(metadata %struct.s* %input, metadata !4, metadata !17), !dbg !18
-  ret i32 42
+  ret i32 42, !dbg !18
 }
 
+; DWARF-LABEL: .debug_info contents:
+
+; DWARF-LABEL: DW_TAG_subprogram
+; DWARF:   DW_AT_frame_base [DW_FORM_exprloc]      (<0x1> 57 )
+;                                                       0x57 -> RSP
+; DWARF:   DW_AT_name [DW_FORM_strp]       ( {{.*}}"f0")
+; DWARF:   DW_TAG_formal_parameter
+; DWARF-NEXT:     DW_AT_location [DW_FORM_exprloc]      (<0x2> 91 08 )
+;                                                        DW_OP_fbreg (0x91) 0x08
+; DWARF-NEXT:     DW_AT_name [DW_FORM_strp]     ( {{.*}}"input")
+
+
+; Dynamic alloca forces the use of RBP as the base pointer
+
 ; CHECK-LABEL: f1:
-; CHECK: DEBUG_VALUE: f:input <- [%RBP+16]
+; CHECK: pushq %rbp
+; CHECK: movl $42, %eax
+; CHECK: popq %rbp
+; CHECK: retq
 define i32 @f1(%struct.s* byval align 8 %input) !dbg !19 {
   %val = load i64, i64* @glob
   ; this alloca should force FP usage.
   %stackspace = alloca i32, i64 %val, align 1
   store i32* %stackspace, i32** @ptr
   call void @llvm.dbg.declare(metadata %struct.s* %input, metadata !20, metadata !17), !dbg !21
-  ret i32 42
+  ret i32 42, !dbg !21
 }
 
+; DWARF-LABEL: DW_TAG_subprogram
+; DWARF:   DW_AT_frame_base [DW_FORM_exprloc]      (<0x1> 56 )
+;                                                       0x56 -> RBP
+; DWARF:   DW_AT_name [DW_FORM_strp]       ( {{.*}}"f1")
+; DWARF:   DW_TAG_formal_parameter
+; DWARF-NEXT:     DW_AT_location [DW_FORM_exprloc]      (<0x2> 91 10 )
+;                                                        DW_OP_fbreg (0x91) 0x10
+; DWARF-NEXT:     DW_AT_name [DW_FORM_strp]     ( {{.*}}"input")
+
 ; CHECK-LABEL: f2:
 ; Just check that we are indeed aligning the stack and setting up a base pointer
 ; in RBX.
@@ -34,33 +65,40 @@ define i32 @f1(%struct.s* byval align 8 %input) !dbg !19 {
 ; CHECK: andq $-64, %rsp
 ; CHECK: subq $64, %rsp
 ; CHECK: movq %rsp, %rbx
-; The parameter should still be referenced through RBP though.
-; CHECK-NOT: DEBUG_VALUE: f:input <- [%RBX
-; CHECK: DEBUG_VALUE: f:input <- [%RBP+16]
 define i32 @f2(%struct.s* byval align 8 %input) !dbg !22 {
   %val = load i64, i64* @glob
   %stackspace = alloca i32, i64 %val, align 64
   store i32* %stackspace, i32** @ptr
   call void @llvm.dbg.declare(metadata %struct.s* %input, metadata !23, metadata !17), !dbg !24
-  ret i32 42
+  ret i32 42, !dbg !24
 }
 
+; "input" should still be referred to through RBP.
+; DWARF-LABEL: DW_TAG_subprogram
+; DWARF:   DW_AT_frame_base [DW_FORM_exprloc]      (<0x1> 56 )
+;                                                       0x56 -> RBP
+; DWARF:   DW_AT_name [DW_FORM_strp]       ( {{.*}}"f2")
+; DWARF:   DW_TAG_formal_parameter
+; DWARF-NEXT:     DW_AT_location [DW_FORM_exprloc]      (<0x2> 91 10 )
+;                                                        DW_OP_fbreg (0x91) 0x10
+; DWARF-NEXT:     DW_AT_name [DW_FORM_strp]     ( {{.*}}"input")
+
 declare void @llvm.dbg.declare(metadata, metadata, metadata)
 
 !llvm.dbg.cu = !{!2}
 !llvm.module.flags = !{!0, !1}
 
 !0 = !{i32 2, !"Dwarf Version", i32 4}
 !1 = !{i32 2, !"Debug Info Version", i32 3}
-!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, emissionKind: FullDebug)
 !3 = !DIFile(filename: "dbg-baseptr.ll", directory: "/")
 !4 = !DILocalVariable(name: "input", arg: 1, scope: !8, file: !3, line: 5, type: !9)
 !5 = !{}
 
 !6 = !DISubroutineType(types: !7)
 !7 = !{!10, !9}
 
-!8 = distinct !DISubprogram(name: "f", file: !3, line: 5, type: !6, isLocal: false, isDefinition: true, flags: DIFlagPrototyped, unit: !2, variables: !5)
+!8 = distinct !DISubprogram(name: "f0", file: !3, line: 5, type: !6, isLocal: false, isDefinition: true, unit: !2, variables: !5)
 
 !9 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "s", elements: !11)
 !10 = !DIBasicType(name: "unsigned int", size: 32, encoding: DW_ATE_unsigned)
@@ -74,9 +112,9 @@ declare void @llvm.dbg.declare(metadata, metadata, metadata)
 !17 = !DIExpression()
 !18 = !DILocation(line: 5, scope: !8)
 
-!19 = distinct !DISubprogram(name: "f", file: !3, line: 5, type: !6, isLocal: false, isDefinition: true, flags: DIFlagPrototyped, unit: !2, variables: !5)
+!19 = distinct !DISubprogram(name: "f1", file: !3, line: 5, type: !6, isLocal: false, isDefinition: true, flags: DIFlagPrototyped, unit: !2, variables: !5)
 !20 = !DILocalVariable(name: "input", arg: 1, scope: !19, file: !3, line: 5, type: !9)
 !21 = !DILocation(line: 5, scope: !19)
-!22 = distinct !DISubprogram(name: "f", file: !3, line: 5, type: !6, isLocal: false, isDefinition: true, flags: DIFlagPrototyped, unit: !2, variables: !5)
+!22 = distinct !DISubprogram(name: "f2", file: !3, line: 5, type: !6, isLocal: false, isDefinition: true, flags: DIFlagPrototyped, unit: !2, variables: !5)
 !23 = !DILocalVariable(name: "input", arg: 1, scope: !22, file: !3, line: 5, type: !9)
 !24 = !DILocation(line: 5, scope: !22)
diff --git a/llvm/test/DebugInfo/X86/dbg-declare-inalloca.ll b/llvm/test/DebugInfo/X86/dbg-declare-inalloca.ll
