Revert "[DebugInfo] Introduce DW_OP_LLVM_convert"

This reverts commit 1cf4b593a7ebd666fc6775f3bd38196e8e65fafe.

Build bots found failing tests not detected locally.

Failing Tests (3):
  LLVM :: DebugInfo/Generic/convert-debugloc.ll
  LLVM :: DebugInfo/Generic/convert-inlined.ll
  LLVM :: DebugInfo/Generic/convert-linked.ll

llvm-svn: 356444

1 files changed, 15 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 9271e1dda5a..d14384fe576 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1861,10 +1861,21 @@ bool llvm::replaceAllDbgUsesWith(Instruction &From, Value &To,
         return None;
 
       bool Signed = *Signedness == DIBasicType::Signedness::Signed;
-      dwarf::TypeKind TK = Signed ? dwarf::DW_ATE_signed : dwarf::DW_ATE_unsigned;
-      SmallVector<uint64_t, 8> Ops({dwarf::DW_OP_LLVM_convert, ToBits, TK,
-                                   dwarf::DW_OP_LLVM_convert, FromBits, TK});
-      return DIExpression::appendToStack(DII.getExpression(), Ops);
+
+      if (!Signed) {
+        // In the unsigned case, assume that a debugger will initialize the
+        // high bits to 0 and do a no-op conversion.
+        return Identity(DII);
+      } else {
+        // In the signed case, the high bits are given by sign extension, i.e:
+        //   (To >> (ToBits - 1)) * ((2 ^ FromBits) - 1)
+        // Calculate the high bits and OR them together with the low bits.
+        SmallVector<uint64_t, 8> Ops({dwarf::DW_OP_dup, dwarf::DW_OP_constu,
+                                      (ToBits - 1), dwarf::DW_OP_shr,
+                                      dwarf::DW_OP_lit0, dwarf::DW_OP_not,
+                                      dwarf::DW_OP_mul, dwarf::DW_OP_or});
+        return DIExpression::appendToStack(DII.getExpression(), Ops);
+      }
     };
     return rewriteDebugUsers(From, To, DomPoint, DT, SignOrZeroExt);
   }