Revert r358268 "[DebugInfo] DW_OP_deref_size in PrologEpilogInserter."

It causes clang to crash while building Chromium. See https://crbug.com/952230
for reproducer.

> The PrologEpilogInserter need to insert a DW_OP_deref_size before
> prepending a memory location expression to an already implicit
> expression to avoid having the existing expression act on the memory
> address instead of the value behind it.
>
> The reason for using DW_OP_deref_size and not plain DW_OP_deref is that
> big-endian targets need to read the right size as simply truncating a
> larger read would yield the wrong result (LSB bytes are not at the lower
> address).
>
> Differential Revision: https://reviews.llvm.org/D59687

llvm-svn: 358281

6 files changed, 3 insertions, 99 deletions

diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
index 357074a3649..2ec8de14d66 100644
--- a/llvm/include/llvm/IR/DebugInfoMetadata.h
+++ b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -2510,9 +2510,6 @@ public:
   /// Return whether this is a piece of an aggregate variable.
   bool isFragment() const { return getFragmentInfo().hasValue(); }
 
-  /// Return whether this is an implicit location description.
-  bool isImplicit() const;
-
   /// Append \p Ops with operations to apply the \p Offset.
   static void appendOffset(SmallVectorImpl<uint64_t> &Ops, int64_t Offset);
 
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index 48f8addd031..41fa45f2507 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -434,10 +434,6 @@ void DwarfExpression::addExpression(DIExpressionCursor &&ExprCursor,
       assert(LocationKind != Register);
       emitOp(dwarf::DW_OP_xderef);
       break;
-    case dwarf::DW_OP_deref_size:
-      emitOp(dwarf::DW_OP_deref_size);
-      emitUnsigned(Op->getArg(0));
-      break;
     default:
       llvm_unreachable("unhandled opcode found in expression");
     }
diff --git a/llvm/lib/CodeGen/MIRParser/MIParser.cpp b/llvm/lib/CodeGen/MIRParser/MIParser.cpp
index d414b6a0b4b..971944be2f9 100644
--- a/llvm/lib/CodeGen/MIRParser/MIParser.cpp
+++ b/llvm/lib/CodeGen/MIRParser/MIParser.cpp
@@ -1854,11 +1854,6 @@ bool MIParser::parseDIExpression(MDNode *&Expr) {
           Elements.push_back(Op);
           continue;
         }
-        if (unsigned Enc = dwarf::getAttributeEncoding(Token.stringValue())) {
-          lex();
-          Elements.push_back(Enc);
-          continue;
-        }
         return error(Twine("invalid DWARF op '") + Token.stringValue() + "'");
       }
 
diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index 31f962eba42..67834c8c352 100644
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -1172,22 +1172,12 @@ void PEI::replaceFrameIndices(MachineBasicBlock *BB, MachineFunction &MF,
         assert(i == 0 && "Frame indices can only appear as the first "
                          "operand of a DBG_VALUE machine instruction");
         unsigned Reg;
-        unsigned FrameIdx = MI.getOperand(0).getIndex();
-        unsigned Size = MF.getFrameInfo().getObjectSize(FrameIdx);
-
         int64_t Offset =
-            TFI->getFrameIndexReference(MF, FrameIdx, Reg);
+            TFI->getFrameIndexReference(MF, MI.getOperand(0).getIndex(), Reg);
         MI.getOperand(0).ChangeToRegister(Reg, false /*isDef*/);
         MI.getOperand(0).setIsDebug();
-
-        const DIExpression *DIExpr = MI.getDebugExpression();
-        // If we already have a Implicit location expression we need to insert
-        // a deref before prepending a Memory location expression.
-        if (DIExpr->isImplicit()) {
-          SmallVector<uint64_t, 2> Ops = {dwarf::DW_OP_deref_size, Size};
-          DIExpr = DIExpression::prependOpcodes(DIExpr, Ops, DIExpression::WithStackValue);
-        }
-        DIExpr = DIExpression::prepend(DIExpr, DIExpression::NoDeref, Offset);
+        auto *DIExpr = DIExpression::prepend(MI.getDebugExpression(),
+                                             DIExpression::NoDeref, Offset);
         MI.getOperand(3).setMetadata(DIExpr);
         continue;
       }
diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index 4ef38b6f7fe..7158e5764fa 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -833,7 +833,6 @@ unsigned DIExpression::ExprOperand::getSize() const {
   case dwarf::DW_OP_LLVM_fragment:
     return 3;
   case dwarf::DW_OP_constu:
-  case dwarf::DW_OP_deref_size:
   case dwarf::DW_OP_plus_uconst:
     return 2;
   default:
@@ -890,7 +889,6 @@ bool DIExpression::isValid() const {
     case dwarf::DW_OP_shr:
     case dwarf::DW_OP_shra:
     case dwarf::DW_OP_deref:
-    case dwarf::DW_OP_deref_size:
     case dwarf::DW_OP_xderef:
     case dwarf::DW_OP_lit0:
     case dwarf::DW_OP_not:
@@ -901,19 +899,6 @@ bool DIExpression::isValid() const {
   return true;
 }
 
-bool DIExpression::isImplicit() const {
-  unsigned N = getNumElements();
-  if (isValid() && N > 0) {
-    switch (getElement(N-1)) {
-      case dwarf::DW_OP_stack_value: return true;
-      case dwarf::DW_OP_LLVM_fragment:
-        return N > 1 && getElement(N-2) == dwarf::DW_OP_stack_value;
-      default: break;
-    }
-  }
-  return false;
-}
-
 Optional<DIExpression::FragmentInfo>
 DIExpression::getFragmentInfo(expr_op_iterator Start, expr_op_iterator End) {
   for (auto I = Start; I != End; ++I)
diff --git a/llvm/test/CodeGen/X86/prologepilog_deref_size.mir b/llvm/test/CodeGen/X86/prologepilog_deref_size.mir
deleted file mode 100644
index 0b0ea5d881e..00000000000
--- a/llvm/test/CodeGen/X86/prologepilog_deref_size.mir
+++ /dev/null
@@ -1,59 +0,0 @@
-# RUN: llc -run-pass=prologepilog -o - %s | FileCheck %s
---- |
-  ; ModuleID = 'dbg.opt.ll'
-  source_filename = "dbg.c"
-  target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
-  target triple = "x86_64-unknown-linux-gnu"
-
-  ; Function Attrs: noinline nounwind uwtable
-  define dso_local zeroext i16 @foo(i16 zeroext %d0, i16 zeroext %d1, i16 zeroext %d2, i16 zeroext %d3, i16 zeroext %d4, i16 zeroext %d5, i16 zeroext %d6, i16 zeroext %d7, i16 zeroext %d8, i16 signext %x) #0 !dbg !7 {
-  entry:
-    call void @llvm.dbg.value(metadata i16 %x, metadata !32, metadata !DIExpression(DW_OP_LLVM_convert, 16, DW_ATE_signed, DW_OP_LLVM_convert, 32, DW_ATE_signed, DW_OP_stack_value)), !dbg !34
-    ret i16 %x
-  }
-
-  ; Function Attrs: nounwind readnone speculatable
-  declare void @llvm.dbg.value(metadata, metadata, metadata) #1
-
-  attributes #0 = { noinline nounwind uwtable }
-  attributes #1 = { nounwind readnone speculatable }
-
-  !llvm.dbg.cu = !{!0}
-  !llvm.module.flags = !{!3, !4, !5}
-  !llvm.ident = !{!6}
-
-  !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 9.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
-  !1 = !DIFile(filename: "dbg.c", directory: "/tmp")
-  !2 = !{}
-  !3 = !{i32 2, !"Dwarf Version", i32 4}
-  !4 = !{i32 2, !"Debug Info Version", i32 3}
-  !5 = !{i32 1, !"wchar_size", i32 4}
-  !6 = !{!"clang version 9.0.0"}
-  !7 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 2, type: !8, scopeLine: 2, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
-  !8 = !DISubroutineType(types: !9)
-  !9 = !{!10, !10, !10, !10, !10, !10, !10, !10, !10, !10, !10}
-  !10 = !DIDerivedType(tag: DW_TAG_typedef, name: "T", file: !1, line: 1, baseType: !11)
-  !11 = !DIBasicType(name: "signed short", size: 16, encoding: DW_ATE_signed)
-  !32 = !DILocalVariable(name: "y", scope: !7, file: !1, line: 3, type: !33)
-  !33 = !DIBasicType(name: "signed int", size: 32, encoding: DW_ATE_signed)
-  !34 = !DILocation(line: 3, column: 20, scope: !7)
-
-...
----
-name:            foo
-tracksRegLiveness: true
-fixedStack:
-  - { id: 0, type: default, offset: 24, size: 2, alignment: 8, stack-id: 0,
-      isImmutable: true, isAliased: false, callee-saved-register: '', callee-saved-restored: true,
-      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
-stack:           []
-constants:       []
-machineFunctionInfo: {}
-body:             |
-  bb.0.entry:
-    renamable $ax = MOV16rm %fixed-stack.0, 1, $noreg, 0, $noreg :: (load 2 from %fixed-stack.0, align 8)
-    DBG_VALUE %fixed-stack.0, 0, !32, !DIExpression(DW_OP_LLVM_convert, 16, DW_ATE_signed, DW_OP_LLVM_convert, 32, DW_ATE_signed, DW_OP_stack_value), debug-location !34
-    RET 0, $ax
-...
-# CHECK: machineFunctionInfo
-# CHECK: DIExpression(DW_OP_plus_uconst, {{[0-9]+}}, DW_OP_deref_size, 2, DW_OP_LLVM_convert, 16, DW_ATE_signed, DW_OP_LLVM_convert, 32, DW_ATE_signed, DW_OP_stack_value)