Merge pull request #2068 from apple/revert-2060-eng/PR-70307714

Revert "[DebugInfo] Fix legacy ZExt emission when FromBits >= 64 (PR47927)"

Author: vedantk

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp

@@ -558,7 +558,7 @@ void DwarfExpression::addExpression(DIExpressionCursor &&ExprCursor,
           if (Encoding == dwarf::DW_ATE_signed)
             emitLegacySExt(PrevConvertOp->getArg(0));
           else if (Encoding == dwarf::DW_ATE_unsigned)
-            emitLegacyZExt(PrevConvertOp->getArg(0), BitSize);
+            emitLegacyZExt(PrevConvertOp->getArg(0));
           PrevConvertOp = None;
         } else {
           PrevConvertOp = Op;
@@ -650,17 +650,11 @@ void DwarfExpression::emitLegacySExt(unsigned FromBits) {
   emitOp(dwarf::DW_OP_or);
 }
 
-void DwarfExpression::emitLegacyZExt(unsigned FromBits, unsigned ToBits) {
-  if (FromBits < 64) {
-    // X & ((1 << FromBits) - 1)
-    emitOp(dwarf::DW_OP_constu);
-    emitUnsigned((1ULL << FromBits) - 1);
-    emitOp(dwarf::DW_OP_and);
-  } else {
-    addOpPiece(FromBits, 0);
-    emitOp(dwarf::DW_OP_lit0);
-    addOpPiece(ToBits - FromBits, FromBits);
-  }
+void DwarfExpression::emitLegacyZExt(unsigned FromBits) {
+  // (X & (1 << FromBits - 1))
+  emitOp(dwarf::DW_OP_constu);
+  emitUnsigned((1ULL << FromBits) - 1);
+  emitOp(dwarf::DW_OP_and);
 }
 
 void DwarfExpression::addWasmLocation(unsigned Index, uint64_t Offset) {

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h

@@ -351,7 +351,7 @@ class DwarfExpression {
   void addFragmentOffset(const DIExpression *Expr);
 
   void emitLegacySExt(unsigned FromBits);
-  void emitLegacyZExt(unsigned FromBits, unsigned ToBits);
+  void emitLegacyZExt(unsigned FromBits);
 
   /// Emit location information expressed via WebAssembly location + offset
   /// The Index is an identifier for locals, globals or operand stack.