Remove PrologEpilogInserter's usage of DBG_VALUE's offset field

In the last half-dozen commits to LLVM I removed code that became dead
after removing the offset parameter from llvm.dbg.value gradually
proceeding from IR towards the backend. Before I can move on to
DwarfDebug and friends there is one last side-called offset I need to
remove:  This patch modifies PrologEpilogInserter's use of the
DBG_VALUE's offset argument to use a DIExpression instead. Because the
PrologEpilogInserter runs at the Machine level I had to play a little
trick with a named llvm.dbg.mir node to get the DIExpressions to print
in MIR dumps (which print the llvm::Module followed by the
MachineFunction dump).

I also had to add rudimentary DwarfExpression support to CodeView and
as a side-effect also fixed a bug (CodeViewDebug::collectVariableInfo
was supposed to give up on variables with complex DIExpressions, but
would fail to do so for fragments, which are also modeled as
DIExpressions).

With this last holdover removed we will have only one canonical way of
representing offsets to debug locations which will simplify the code
in DwarfDebug (and future versions of CodeViewDebug once it starts
handling more complex expressions) and make it easier to reason about.

This patch is NFC-ish: All test case changes are for assembler
comments and the binary output does not change.

rdar://problem/33580047
Differential Revision: https://reviews.llvm.org/D36125

llvm-svn: 309751

12 files changed, 42 insertions, 18 deletions

diff --git a/llvm/include/llvm/CodeGen/MachineOperand.h b/llvm/include/llvm/CodeGen/MachineOperand.h
index 2560399bcf5..f1e6ac77860 100644
--- a/llvm/include/llvm/CodeGen/MachineOperand.h
+++ b/llvm/include/llvm/CodeGen/MachineOperand.h
@@ -549,6 +549,11 @@ public:
     Contents.OffsetedInfo.Val.Index = Idx;
   }
 
+  void setMetadata(const MDNode *MD) {
+    assert(isMetadata() && "Wrong MachineOperand mutator");
+    Contents.MD = MD;
+  }
+
   void setMBB(MachineBasicBlock *MBB) {
     assert(isMBB() && "Wrong MachineOperand mutator");
     Contents.MBB = MBB;
diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 38ae15cbd98..833e5bae1cf 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "CodeViewDebug.h"
+#include "DwarfExpression.h"
 #include "llvm/ADT/APSInt.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
@@ -983,17 +984,29 @@ void CodeViewDebug::collectVariableInfo(const DISubprogram *SP) {
       const MachineInstr *DVInst = Range.first;
       assert(DVInst->isDebugValue() && "Invalid History entry");
       const DIExpression *DIExpr = DVInst->getDebugExpression();
+      bool InMemory = DVInst->getOperand(1).isImm();
       bool IsSubfield = false;
       unsigned StructOffset = 0;
+      // Recognize a +Offset expression.
+      int Offset = 0;
+      DIExpressionCursor Ops(DIExpr);
+      auto Op = Ops.peek();
+      if (Op && Op->getOp() == dwarf::DW_OP_plus_uconst) {
+        Offset = Op->getArg(0);
+        Ops.take();
+      }
 
       // Handle fragments.
-      auto Fragment = DIExpr->getFragmentInfo();
+      auto Fragment = Ops.getFragmentInfo();
       if (Fragment) {
         IsSubfield = true;
         StructOffset = Fragment->OffsetInBits / 8;
-      } else if (DIExpr->getNumElements() > 0) {
-        continue; // Ignore unrecognized exprs.
       }
+      // Ignore unrecognized exprs.
+      if (Ops.peek() && Ops.peek()->getOp() != dwarf::DW_OP_LLVM_fragment)
+        continue;
+      if (!InMemory && Offset)
+        continue;
 
       // Bail if operand 0 is not a valid register. This means the variable is a
       // simple constant, or is described by a complex expression.
@@ -1006,8 +1019,6 @@ void CodeViewDebug::collectVariableInfo(const DISubprogram *SP) {
 
       // Handle the two cases we can handle: indirect in memory and in register.
       unsigned CVReg = TRI->getCodeViewRegNum(Reg);
-      bool InMemory = DVInst->getOperand(1).isImm();
-      int Offset = InMemory ? DVInst->getOperand(1).getImm() : 0;
       {
         LocalVarDefRange DR;
         DR.CVRegister = CVReg;
diff --git a/llvm/lib/CodeGen/MachineModuleInfo.cpp b/llvm/lib/CodeGen/MachineModuleInfo.cpp
index 825290a438a..3999cd5eb7e 100644
--- a/llvm/lib/CodeGen/MachineModuleInfo.cpp
+++ b/llvm/lib/CodeGen/MachineModuleInfo.cpp
@@ -16,6 +16,7 @@
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Module.h"
@@ -209,7 +210,8 @@ bool MachineModuleInfo::doInitialization(Module &M) {
   DbgInfoAvailable = UsesVAFloatArgument = UsesMorestackAddr = false;
   AddrLabelSymbols = nullptr;
   TheModule = &M;
-
+  if (getDebugMetadataVersionFromModule(M))
+    M.getOrInsertNamedMetadata("llvm.dbg.mir");
   return false;
 }
 
diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index 63c839fcb0b..cbb43203b5c 100644
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -31,6 +31,7 @@
 #include "llvm/CodeGen/RegisterScavenging.h"
 #include "llvm/CodeGen/StackProtector.h"
 #include "llvm/CodeGen/WinEHFuncInfo.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/LLVMContext.h"
@@ -1079,11 +1080,15 @@ void PEI::replaceFrameIndices(MachineBasicBlock *BB, MachineFunction &Fn,
         assert(i == 0 && "Frame indices can only appear as the first "
                          "operand of a DBG_VALUE machine instruction");
         unsigned Reg;
-        MachineOperand &Offset = MI.getOperand(1);
-        Offset.setImm(
-            Offset.getImm() +
-            TFI->getFrameIndexReference(Fn, MI.getOperand(0).getIndex(), Reg));
+        int64_t Offset =
+            TFI->getFrameIndexReference(Fn, MI.getOperand(0).getIndex(), Reg);
         MI.getOperand(0).ChangeToRegister(Reg, false /*isDef*/);
+        auto *DIExpr = DIExpression::prepend(MI.getDebugExpression(),
+                                             DIExpression::NoDeref, Offset);
+        MI.getOperand(3).setMetadata(DIExpr);
+        const Module *M = Fn.getMMI().getModule();
+        // Add the expression to the metadata graph so isn't lost in MIR dumps.
+        M->getNamedMetadata("llvm.dbg.mir")->addOperand(DIExpr);
         continue;
       }
 
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 454a56a7692..e7362ea99b5 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -736,7 +736,7 @@ void Verifier::visitNamedMDNode(const NamedMDNode &NMD) {
   // There used to be various other llvm.dbg.* nodes, but we don't support
   // upgrading them and we want to reserve the namespace for future uses.
   if (NMD.getName().startswith("llvm.dbg."))
-    AssertDI(NMD.getName() == "llvm.dbg.cu",
+    AssertDI(NMD.getName() == "llvm.dbg.cu" || NMD.getName() == "llvm.dbg.mir",
              "unrecognized named metadata node in the llvm.dbg namespace",
              &NMD);
   for (const MDNode *MD : NMD.operands()) {
diff --git a/llvm/test/CodeGen/ARM/debug-info-arg.ll b/llvm/test/CodeGen/ARM/debug-info-arg.ll
index 5cf78f57dbc..026d45853d7 100644
--- a/llvm/test/CodeGen/ARM/debug-info-arg.ll
+++ b/llvm/test/CodeGen/ARM/debug-info-arg.ll
@@ -11,7 +11,7 @@ define void @foo(%struct.tag_s* nocapture %this, %struct.tag_s* %c, i64 %x, i64
   tail call void @llvm.dbg.value(metadata %struct.tag_s* %c, metadata !13, metadata !DIExpression()), !dbg !21
   tail call void @llvm.dbg.value(metadata i64 %x, metadata !14, metadata !DIExpression()), !dbg !22
   tail call void @llvm.dbg.value(metadata i64 %y, metadata !17, metadata !DIExpression()), !dbg !23
-;CHECK:	@DEBUG_VALUE: foo:y <- [%R7+8]
+;CHECK:	@DEBUG_VALUE: foo:y <- [DW_OP_plus_uconst 8] [%R7+0]
   tail call void @llvm.dbg.value(metadata %struct.tag_s* %ptr1, metadata !18, metadata !DIExpression()), !dbg !24
   tail call void @llvm.dbg.value(metadata %struct.tag_s* %ptr2, metadata !19, metadata !DIExpression()), !dbg !25
   %1 = icmp eq %struct.tag_s* %c, null, !dbg !26
diff --git a/llvm/test/DebugInfo/ARM/PR16736.ll b/llvm/test/DebugInfo/ARM/PR16736.ll
index 59fb225902c..331495e8e91 100644
--- a/llvm/test/DebugInfo/ARM/PR16736.ll
+++ b/llvm/test/DebugInfo/ARM/PR16736.ll
@@ -2,7 +2,7 @@
 ; RUN: llc -filetype=obj < %s \
 ; RUN:   | llvm-dwarfdump - | FileCheck %s --check-prefix=DWARF
 ;
-; CHECK: @DEBUG_VALUE: h:x <- [%R{{.*}}+{{.*}}]
+; CHECK: @DEBUG_VALUE: h:x <- [DW_OP_plus_uconst {{.*}}] [%R{{.*}}+0]
 ; DWARF: Location description: {{7[0-9] [0-9]+ $}}
 ;                              DW_OP_breg. +..
 ; generated from:
diff --git a/llvm/test/DebugInfo/COFF/pieces.ll b/llvm/test/DebugInfo/COFF/pieces.ll
index 0832904ad4f..6d363cf5443 100644
--- a/llvm/test/DebugInfo/COFF/pieces.ll
+++ b/llvm/test/DebugInfo/COFF/pieces.ll
@@ -89,7 +89,7 @@
 ; ASM:         callq   g
 ; ASM:         movl    %eax, [[offset_o_x:[0-9]+]](%rsp)          # 4-byte Spill
 ; ASM: [[spill_o_x_start:\.Ltmp[0-9]+]]:
-; ASM:         #DEBUG_VALUE: bitpiece_spill:o <- [DW_OP_LLVM_fragment 32 32] [%RSP+[[offset_o_x]]]
+; ASM:         #DEBUG_VALUE: bitpiece_spill:o <- [DW_OP_plus_uconst [[offset_o_x]], DW_OP_LLVM_fragment 32 32] [%RSP+0]
 ; ASM:         #APP
 ; ASM:         #NO_APP
 ; ASM:         movl    [[offset_o_x]](%rsp), %eax          # 4-byte Reload
diff --git a/llvm/test/DebugInfo/X86/bbjoin.ll b/llvm/test/DebugInfo/X86/bbjoin.ll
index 2307a97b315..d9d0b1707df 100644
--- a/llvm/test/DebugInfo/X86/bbjoin.ll
+++ b/llvm/test/DebugInfo/X86/bbjoin.ll
@@ -9,10 +9,11 @@
 ;     ++x;
 ;   return x; // check that x is not a constant here.
 ; }
+; CHECK: ![[EXPR:.*]] = !DIExpression(DW_OP_plus_uconst, 4, DW_OP_deref)
 ; CHECK: ![[X:.*]] = !DILocalVariable(name: "x",
 ; CHECK: bb.0.entry:
 ; CHECK:   DBG_VALUE 23, 0, ![[X]],
-; CHECK:   DBG_VALUE %rsp, 4, ![[X]]
+; CHECK:   DBG_VALUE %rsp, 0, ![[X]], ![[EXPR]],
 ; CHECK: bb.1.if.then:
 ; CHECK:   DBG_VALUE 43, 0, ![[X]],
 ; CHECK: bb.2.if.end:
diff --git a/llvm/test/DebugInfo/X86/dbg-value-frame-index.ll b/llvm/test/DebugInfo/X86/dbg-value-frame-index.ll
index 0ac4dde3df0..30d91c8051e 100644
--- a/llvm/test/DebugInfo/X86/dbg-value-frame-index.ll
+++ b/llvm/test/DebugInfo/X86/dbg-value-frame-index.ll
@@ -20,7 +20,7 @@ while.end:
 }
 
 ; CHECK-LABEL: test
-; CHECK:       #DEBUG_VALUE: test:w <- [%RSP+8]
+; CHECK:       #DEBUG_VALUE: test:w <- [DW_OP_plus_uconst 8] [%RSP+0]
 ; DWARF:       Location description: 77 08
 ;                                    DW_OP_breg7 +8
 
diff --git a/llvm/test/DebugInfo/X86/debug-loc-asan.ll b/llvm/test/DebugInfo/X86/debug-loc-asan.ll
index ece93b9e89f..00790a4f092 100644
--- a/llvm/test/DebugInfo/X86/debug-loc-asan.ll
+++ b/llvm/test/DebugInfo/X86/debug-loc-asan.ll
@@ -17,7 +17,7 @@
 ; CHECK: #DEBUG_VALUE: bar:y <- [DW_OP_deref] [%RDI+0]
 ; CHECK: movq %rdi, [[OFFSET:[0-9]+]](%rsp)
 ; CHECK-NEXT: [[START_LABEL:.Ltmp[0-9]+]]
-; CHECK-NEXT: #DEBUG_VALUE: bar:y <- [DW_OP_deref, DW_OP_deref]
+; CHECK-NEXT: #DEBUG_VALUE: bar:y <- [DW_OP_plus_uconst [[OFFSET]], DW_OP_deref, DW_OP_deref]
 ; This location should be valid until the end of the function.
 
 ; CHECK:        movq    %rbp, %rsp
diff --git a/llvm/test/DebugInfo/X86/pieces-4.ll b/llvm/test/DebugInfo/X86/pieces-4.ll
index 105f4bed16d..c210272ed29 100644
--- a/llvm/test/DebugInfo/X86/pieces-4.ll
+++ b/llvm/test/DebugInfo/X86/pieces-4.ll
@@ -17,7 +17,7 @@
 ; CHECK:               callq   g
 ; CHECK:               movl    %eax, [[offs:[0-9]+]](%rsp)          # 4-byte Spill
 ; CHECK:               #DEBUG_VALUE: bitpiece_spill:o <- [DW_OP_LLVM_fragment 32 32] 0
-; CHECK:               #DEBUG_VALUE: bitpiece_spill:o <- [DW_OP_LLVM_fragment 0 32] [%RSP+[[offs]]]
+; CHECK:               #DEBUG_VALUE: bitpiece_spill:o <- [DW_OP_plus_uconst [[offs]], DW_OP_LLVM_fragment 0 32] [%RSP+0]
 ; CHECK:               #APP
 ; CHECK:               #NO_APP
 ; CHECK:               movl    [[offs]](%rsp), %eax          # 4-byte Reload