Revert "[DebugInfo] Refactor code for emitting DWARF expressions for FP constants"

The commit introduced a crash when emitting (debug info for) complex
floats (pr48277).

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -2466,11 +2466,24 @@ void DwarfDebug::emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
     // TODO TargetIndexLocation is a target-independent. Currently only the WebAssembly-specific
     // encoding is supported.
     DwarfExpr.addWasmLocation(Loc.Index, static_cast<uint64_t>(Loc.Offset));
-    DwarfExpr.addExpression(std::move(ExprCursor));
-    return;
+      DwarfExpr.addExpression(std::move(ExprCursor));
+      return;
   } else if (Value.isConstantFP()) {
-    DwarfExpr.addConstantFP(Value.getConstantFP()->getValueAPF(), AP);
-    return;
+    if (AP.getDwarfVersion() >= 4 && !AP.getDwarfDebug()->tuneForSCE()) {
+      DwarfExpr.addConstantFP(Value.getConstantFP()->getValueAPF(), AP);
+      return;
+    } else if (Value.getConstantFP()
+                   ->getValueAPF()
+                   .bitcastToAPInt()
+                   .getBitWidth() <= 64 /*bits*/)
+      DwarfExpr.addUnsignedConstant(
+          Value.getConstantFP()->getValueAPF().bitcastToAPInt());
+    else
+      LLVM_DEBUG(
+          dbgs()
+          << "Skipped DwarfExpression creation for ConstantFP of size"
+          << Value.getConstantFP()->getValueAPF().bitcastToAPInt().getBitWidth()
+          << " bits\n");
   }
   DwarfExpr.addExpression(std::move(ExprCursor));
 }

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp

@@ -200,29 +200,10 @@ void DwarfExpression::addUnsignedConstant(uint64_t Value) {
   emitConstu(Value);
 }
 
-void DwarfExpression::addUnsignedConstant(APInt Value, const AsmPrinter &AP) {
+void DwarfExpression::addUnsignedConstant(const APInt &Value) {
   assert(isImplicitLocation() || isUnknownLocation());
   LocationKind = Implicit;
 
-  if (AP.getDwarfVersion() >= 4 && !AP.getDwarfDebug()->tuneForSCE()) {
-    int NumBytes = Value.getBitWidth() / 8;
-    emitOp(dwarf::DW_OP_implicit_value);
-    emitUnsigned(NumBytes /*Size of the block in bytes*/);
-
-    // The loop below is emitting the value starting at least significant
-    // byte, so we need to perform a byte-swap to get the byte order correct
-    // in case of a big-endian target.
-    if (AP.getDataLayout().isBigEndian())
-      Value = Value.byteSwap();
-
-    for (int i = 0; i < NumBytes; ++i) {
-      emitData1(Value.getRawData()[0] & 0xFF);
-      Value = Value.lshr(8);
-    }
-
-    return;
-  }
-
   unsigned Size = Value.getBitWidth();
   const uint64_t *Data = Value.getRawData();
 
@@ -231,9 +212,9 @@ void DwarfExpression::addUnsignedConstant(APInt Value, const AsmPrinter &AP) {
   unsigned Offset = 0;
   while (Offset < Size) {
     addUnsignedConstant(*Data++);
-    addStackValue();
     if (Offset == 0 && Size <= 64)
       break;
+    addStackValue();
     addOpPiece(std::min(Size - Offset, 64u), Offset);
     Offset += 64;
   }
@@ -243,13 +224,27 @@ void DwarfExpression::addConstantFP(const APFloat &APF, const AsmPrinter &AP) {
   assert(isImplicitLocation() || isUnknownLocation());
   APInt API = APF.bitcastToAPInt();
   int NumBytes = API.getBitWidth() / 8;
-  // FIXME: Add support for `long double`.
-  if (NumBytes <= 8 /*double*/)
-    addUnsignedConstant(API, AP);
-  else
-    LLVM_DEBUG(
-        dbgs() << "Skipped DwarfExpression creation for ConstantFP of size"
-               << API.getBitWidth() << " bits\n");
+  if (NumBytes == 4 /*float*/ || NumBytes == 8 /*double*/) {
+    // FIXME: Add support for `long double`.
+    emitOp(dwarf::DW_OP_implicit_value);
+    emitUnsigned(NumBytes /*Size of the block in bytes*/);
+
+    // The loop below is emitting the value starting at least significant byte,
+    // so we need to perform a byte-swap to get the byte order correct in case
+    // of a big-endian target.
+    if (AP.getDataLayout().isBigEndian())
+      API = API.byteSwap();
+
+    for (int i = 0; i < NumBytes; ++i) {
+      emitData1(API.getZExtValue() & 0xFF);
+      API = API.lshr(8);
+    }
+
+    return;
+  }
+  LLVM_DEBUG(
+      dbgs() << "Skipped DW_OP_implicit_value creation for ConstantFP of size: "
+             << API.getBitWidth() << " bits\n");
 }
 
 bool DwarfExpression::addMachineRegExpression(const TargetRegisterInfo &TRI,

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h

@@ -297,7 +297,7 @@ public:
   void addUnsignedConstant(uint64_t Value);
 
   /// Emit an unsigned constant.
-  void addUnsignedConstant(APInt Value, const AsmPrinter &AP);
+  void addUnsignedConstant(const APInt &Value);
 
   /// Emit an floating point constant.
   void addConstantFP(const APFloat &Value, const AsmPrinter &AP);

llvm/test/DebugInfo/ARM/implicit_value-_Float16.ll

@@ -1,51 +0,0 @@
-; RUN: llc -debugger-tune=gdb -filetype=obj %s -o - | llvm-dwarfdump - \
-; RUN:   | FileCheck %s --check-prefixes=GDB,BOTH
-; RUN: llc -debugger-tune=sce -filetype=obj %s -o - | llvm-dwarfdump - \
-; RUN:   | FileCheck %s --check-prefixes=SCE,BOTH
-
-; BOTH: DW_TAG_variable
-; BOTH-NEXT:  DW_AT_location
-; GDB-NEXT:      {{.*}}: DW_OP_implicit_value 0x2 0xe0 0x51
-; SCE-NEXT:      {{.*}}: DW_OP_constu 0x51e0, DW_OP_stack_value
-; GDB-NEXT:      {{.*}}: DW_OP_implicit_value 0x2 0x40 0x51
-; SCE-NEXT:      {{.*}}: DW_OP_constu 0x5140, DW_OP_stack_value
-; BOTH-NEXT:  DW_AT_name    ("a")
-
-source_filename = "-"
-target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
-target triple = "armv7-unknown-unknown"
-
-define dso_local arm_aapcscc void @f() local_unnamed_addr !dbg !8 {
-entry:
-  call void @llvm.dbg.value(metadata half 0xH51E0, metadata !13, metadata !DIExpression()), !dbg !15
-  call arm_aapcscc void bitcast (void (...)* @g to void ()*)(), !dbg !15
-  call void @llvm.dbg.value(metadata half 0xH5140, metadata !13, metadata !DIExpression()), !dbg !15
-  call arm_aapcscc void bitcast (void (...)* @g to void ()*)(), !dbg !15
-  ret void, !dbg !15
-}
-
-declare dso_local arm_aapcscc void @g(...) local_unnamed_addr
-
-declare void @llvm.dbg.value(metadata, metadata, metadata) #2
-
-attributes #2 = { nofree nosync nounwind readnone speculatable willreturn }
-
-!llvm.dbg.cu = !{!0}
-!llvm.module.flags = !{!3, !4, !5, !6}
-!llvm.ident = !{!7}
-
-!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, emissionKind: FullDebug, enums: !2)
-!1 = !DIFile(filename: "-", directory: "/")
-!2 = !{}
-!3 = !{i32 7, !"Dwarf Version", i32 4}
-!4 = !{i32 2, !"Debug Info Version", i32 3}
-!5 = !{i32 1, !"wchar_size", i32 4}
-!6 = !{i32 1, !"min_enum_size", i32 4}
-!7 = !{!"clang version 12.0.0"}
-!8 = distinct !DISubprogram(name: "f", scope: !1, file: !1, type: !10, unit: !0)
-!10 = !DISubroutineType(types: !11)
-!11 = !{null}
-!12 = !{!13}
-!13 = !DILocalVariable(name: "a", scope: !8, file: !1, type: !14)
-!14 = !DIBasicType(name: "_Float16", size: 16, encoding: DW_ATE_float)
-!15 = !DILocation(line: 0, scope: !8)