[Utils] Salvage debug info of DCE'ed shl/lhsr/ashr instructions

Here are the number of additional debug values salvaged in a stage2
build of clang:

  1912 SALVAGE: ASHR
   405 SALVAGE: LSHR
   249 SALVAGE: SHL

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@324975 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/AsmPrinter/DwarfExpression.cpp

@@ -347,6 +347,9 @@ void DwarfExpression::addExpression(DIExpressionCursor &&ExprCursor,
     case dwarf::DW_OP_mul:
     case dwarf::DW_OP_or:
     case dwarf::DW_OP_xor:
+    case dwarf::DW_OP_shl:
+    case dwarf::DW_OP_shr:
+    case dwarf::DW_OP_shra:
       emitOp(Op->getOp());
       break;
     case dwarf::DW_OP_deref:

lib/IR/DebugInfoMetadata.cpp

@@ -710,6 +710,9 @@ bool DIExpression::isValid() const {
     case dwarf::DW_OP_mul:
     case dwarf::DW_OP_or:
     case dwarf::DW_OP_xor:
+    case dwarf::DW_OP_shl:
+    case dwarf::DW_OP_shr:
+    case dwarf::DW_OP_shra:
     case dwarf::DW_OP_deref:
     case dwarf::DW_OP_xderef:
       break;

lib/Transforms/Utils/Local.cpp

@@ -1555,6 +1555,15 @@ void llvm::salvageDebugInfo(Instruction &I) {
       case Instruction::Xor:
         applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_xor});
         break;
+      case Instruction::Shl:
+        applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_shl});
+        break;
+      case Instruction::LShr:
+        applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_shr});
+        break;
+      case Instruction::AShr:
+        applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_shra});
+        break;
       default:
         // TODO: Salvage constants from each kind of binop we know about.
         continue;

test/Transforms/InstCombine/debuginfo-variables.ll

@@ -38,6 +38,27 @@ define void @test_sub_pos(i64 %A) {
   ret void
 }
 
+define void @test_shl(i64 %A) {
+; CHECK-LABEL: @test_shl(
+; CHECK-NEXT:  call void @llvm.dbg.value(metadata i64 %A, metadata !37, metadata !DIExpression(DW_OP_constu, 7, DW_OP_shl, DW_OP_stack_value)), !dbg !38
+  %1 = shl i64 %A, 7
+  ret void
+}
+
+define void @test_lshr(i64 %A) {
+; CHECK-LABEL: @test_lshr(
+; CHECK-NEXT:  call void @llvm.dbg.value(metadata i64 %A, metadata !42, metadata !DIExpression(DW_OP_constu, 7, DW_OP_shr, DW_OP_stack_value)), !dbg !43
+  %1 = lshr i64 %A, 7
+  ret void
+}
+
+define void @test_ashr(i64 %A) {
+; CHECK-LABEL: @test_ashr(
+; CHECK-NEXT:  call void @llvm.dbg.value(metadata i64 %A, metadata !47, metadata !DIExpression(DW_OP_constu, 7, DW_OP_shra, DW_OP_stack_value)), !dbg !48
+  %1 = ashr i64 %A, 7
+  ret void
+}
+
 ; CHECK: !8 = !DILocalVariable(name: "1", scope: !5, file: !1, line: 1, type: !9)
 ; CHECK: !10 = !DILocalVariable(name: "2", scope: !5, file: !1, line: 2, type: !11)
 ; CHECK: !12 = !DILocation(line: 2, column: 1, scope: !5)
@@ -54,3 +75,12 @@ define void @test_sub_pos(i64 %A) {
 
 ; CHECK: !32 = !DILocalVariable(name: "6", scope: !30, file: !1, line: 10, type: !11)
 ; CHECK: !33 = !DILocation(line: 10, column: 1, scope: !30)
+
+; CHECK: !37 = !DILocalVariable(name: "7", scope: !35, file: !1, line: 12, type: !11)
+; CHECK: !38 = !DILocation(line: 12, column: 1, scope: !35)
+
+; CHECK: !42 = !DILocalVariable(name: "8", scope: !40, file: !1, line: 14, type: !11)
+; CHECK: !43 = !DILocation(line: 14, column: 1, scope: !40)
+
+; CHECK: !47 = !DILocalVariable(name: "9", scope: !45, file: !1, line: 16, type: !11)
+; CHECK: !48 = !DILocation(line: 16, column: 1, scope: !45)