Revert "[DebugInfo] Enable variadic debug value salvaging"

This reverts commit adace79.
Still breaks things, see comment on https://reviews.llvm.org/D91722

Author: nico

llvm/lib/Transforms/Utils/Local.cpp

@@ -1748,7 +1748,11 @@ void llvm::salvageDebugInfoForDbgValues(
     } else if (isa<DbgValueInst>(DII) &&
                DII->getNumVariableLocationOps() + AdditionalValues.size() <=
                    MaxDebugArgs) {
-      DII->addVariableLocationOps(AdditionalValues, SalvagedExpr);
+      // TODO: Uncomment the line below and delete the two beneath it to enable
+      // salvaging of dbg.values with multiple location operands.
+      // DII->addVariableLocationOps(AdditionalValues, SalvagedExpr);
+      Value *Undef = UndefValue::get(I.getOperand(0)->getType());
+      DII->replaceVariableLocationOp(I.getOperand(0), Undef);
     } else {
       // Do not salvage using DIArgList for dbg.addr/dbg.declare, as it is
       // currently only valid for stack value expressions.

llvm/test/DebugInfo/NVPTX/debug-info.ll

@@ -702,12 +702,12 @@ if.end:                                           ; preds = %if.then, %entry
 ; CHECK-NEXT:	}
 ; CHECK-NEXT:	.section	.debug_info
 ; CHECK-NEXT:	{
-; CHECK-NEXT:.b32 10034                              // Length of Unit
+; CHECK-NEXT:.b32 10029                              // Length of Unit
 ; CHECK-NEXT:.b8 2                                   // DWARF version number
 ; CHECK-NEXT:.b8 0
 ; CHECK-NEXT:.b32 .debug_abbrev                      // Offset Into Abbrev. Section
 ; CHECK-NEXT:.b8 8                                   // Address Size (in bytes)
-; CHECK-NEXT:.b8 1                                   // Abbrev [1] 0xb:0x272b DW_TAG_compile_unit
+; CHECK-NEXT:.b8 1                                   // Abbrev [1] 0xb:0x2726 DW_TAG_compile_unit
 ; CHECK-NEXT:.b8 0                                   // DW_AT_producer
 ; CHECK-NEXT:.b8 4                                   // DW_AT_language
 ; CHECK-NEXT:.b8 0
@@ -8306,7 +8306,7 @@ if.end:                                           ; preds = %if.then, %entry
 ; CHECK-NEXT:.b8 3                                   // DW_AT_decl_line
 ; CHECK-NEXT:.b32 3345                               // DW_AT_type
 ; CHECK-NEXT:.b8 0                                   // End Of Children Mark
-; CHECK-NEXT:.b8 40                                  // Abbrev [40] 0x2671:0xc4 DW_TAG_subprogram
+; CHECK-NEXT:.b8 40                                  // Abbrev [40] 0x2671:0xbf DW_TAG_subprogram
 ; CHECK-NEXT:.b64 Lfunc_begin0                       // DW_AT_low_pc
 ; CHECK-NEXT:.b64 Lfunc_end0                         // DW_AT_high_pc
 ; CHECK-NEXT:.b8 1                                   // DW_AT_frame_base
@@ -8386,7 +8386,7 @@ if.end:                                           ; preds = %if.then, %entry
 ; CHECK-NEXT:.b8 12                                  // DW_AT_call_file
 ; CHECK-NEXT:.b8 6                                   // DW_AT_call_line
 ; CHECK-NEXT:.b8 37                                  // DW_AT_call_column
-; CHECK-NEXT:.b8 43                                  // Abbrev [43] 0x2711:0x23 DW_TAG_inlined_subroutine
+; CHECK-NEXT:.b8 43                                  // Abbrev [43] 0x2711:0x1e DW_TAG_inlined_subroutine
 ; CHECK-NEXT:.b32 9791                               // DW_AT_abstract_origin
 ; CHECK-NEXT:.b64 Ltmp9                              // DW_AT_low_pc
 ; CHECK-NEXT:.b64 Ltmp10                             // DW_AT_high_pc
@@ -8395,8 +8395,6 @@ if.end:                                           ; preds = %if.then, %entry
 ; CHECK-NEXT:.b8 5                                   // DW_AT_call_column
 ; CHECK-NEXT:.b8 44                                  // Abbrev [44] 0x2729:0x5 DW_TAG_formal_parameter
 ; CHECK-NEXT:.b32 9820                               // DW_AT_abstract_origin
-; CHECK-NEXT:.b8 44                                  // Abbrev [44] 0x272e:0x5 DW_TAG_formal_parameter
-; CHECK-NEXT:.b32 9829                               // DW_AT_abstract_origin
 ; CHECK-NEXT:.b8 0                                   // End Of Children Mark
 ; CHECK-NEXT:.b8 0                                   // End Of Children Mark
 ; CHECK-NEXT:.b8 0                                   // End Of Children Mark

llvm/test/DebugInfo/salvage-gep.ll

@@ -1,3 +1,4 @@
+; XFAIL: *
 ; RUN: opt %s -dce -S | FileCheck %s
 
 ; Tests the salvaging of GEP instructions, specifically struct indexing and

llvm/test/DebugInfo/salvage-nonconst-binop.ll

@@ -1,3 +1,4 @@
+; XFAIL: *
 ; RUN: opt %s -dce -S | FileCheck %s
 
 ; Tests the salvaging of binary operators that use more than one non-constant