InstCombine: salvage the debug info of DCE'ed add instructions.

rdar://problem/31209283

llvm-svn: 317522

2 files changed, 131 insertions, 12 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index cb7978f76aa..89dbe4b8fda 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1362,16 +1362,25 @@ void llvm::salvageDebugInfo(Instruction &I) {
   SmallVector<DbgValueInst *, 1> DbgValues;
   auto &M = *I.getModule();
 
-  auto MDWrap = [&](Value *V) {
+  auto wrapMD = [&](Value *V) {
     return MetadataAsValue::get(I.getContext(), ValueAsMetadata::get(V));
   };
 
+  auto applyOffset = [&](DbgValueInst *DVI, uint64_t Offset) {
+    auto *DIExpr = DVI->getExpression();
+    DIExpr = DIExpression::prepend(DIExpr, DIExpression::NoDeref, Offset,
+                                   DIExpression::WithStackValue);
+    DVI->setOperand(0, wrapMD(I.getOperand(0)));
+    DVI->setOperand(2, MetadataAsValue::get(I.getContext(), DIExpr));
+    DEBUG(dbgs() << "SALVAGE: " << *DVI << '\n');
+  };
+
   if (isa<BitCastInst>(&I) || isa<IntToPtrInst>(&I)) {
     findDbgValues(DbgValues, &I);
     for (auto *DVI : DbgValues) {
       // Bitcasts are entirely irrelevant for debug info. Rewrite the dbg.value
       // to use the cast's source.
-      DVI->setOperand(0, MDWrap(I.getOperand(0)));
+      DVI->setOperand(0, wrapMD(I.getOperand(0)));
       DEBUG(dbgs() << "SALVAGE: " << *DVI << '\n');
     }
   } else if (auto *GEP = dyn_cast<GetElementPtrInst>(&I)) {
@@ -1383,24 +1392,26 @@ void llvm::salvageDebugInfo(Instruction &I) {
       // Rewrite a constant GEP into a DIExpression.  Since we are performing
       // arithmetic to compute the variable's *value* in the DIExpression, we
       // need to mark the expression with a DW_OP_stack_value.
-      if (GEP->accumulateConstantOffset(M.getDataLayout(), Offset)) {
-        auto *DIExpr = DVI->getExpression();
+      if (GEP->accumulateConstantOffset(M.getDataLayout(), Offset))
         // GEP offsets are i32 and thus always fit into an int64_t.
-        DIExpr = DIExpression::prepend(DIExpr, DIExpression::NoDeref,
-                                       Offset.getSExtValue(),
-                                       DIExpression::WithStackValue);
-        DVI->setOperand(0, MDWrap(I.getOperand(0)));
-        DVI->setOperand(2, MetadataAsValue::get(I.getContext(), DIExpr));
-        DEBUG(dbgs() << "SALVAGE: " << *DVI << '\n');
-      }
+        applyOffset(DVI, Offset.getSExtValue());
     }
+  } else if (auto *BI = dyn_cast<BinaryOperator>(&I)) {
+    if (BI->getOpcode() == Instruction::Add)
+      if (auto *ConstInt = dyn_cast<ConstantInt>(I.getOperand(1)))
+        if (ConstInt->getBitWidth() <= 64) {
+          APInt Offset = ConstInt->getValue();
+          findDbgValues(DbgValues, &I);
+          for (auto *DVI : DbgValues)
+            applyOffset(DVI, Offset.getSExtValue());
+        }
   } else if (isa<LoadInst>(&I)) {
     findDbgValues(DbgValues, &I);
     for (auto *DVI : DbgValues) {
       // Rewrite the load into DW_OP_deref.
       auto *DIExpr = DVI->getExpression();
       DIExpr = DIExpression::prepend(DIExpr, DIExpression::WithDeref);
-      DVI->setOperand(0, MDWrap(I.getOperand(0)));
+      DVI->setOperand(0, wrapMD(I.getOperand(0)));
       DVI->setOperand(2, MetadataAsValue::get(I.getContext(), DIExpr));
       DEBUG(dbgs() << "SALVAGE:  " << *DVI << '\n');
     }
diff --git a/llvm/test/Transforms/InstCombine/debuginfo_add.ll b/llvm/test/Transforms/InstCombine/debuginfo_add.ll
new file mode 100644
index 00000000000..0d194cc65c7
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/debuginfo_add.ll
@@ -0,0 +1,108 @@
+; RUN: opt -instcombine %s -o - -S | FileCheck %s
+; typedef struct v *v_t;
+; struct v {
+;   unsigned long long p;
+; };
+;  
+; void f(v_t object, unsigned long long *start) {
+;   unsigned head_size;
+;   unsigned long long orig_start;
+;   unsigned long long offset;
+;   orig_start = *start;
+;   for (offset = orig_start - (unsigned long long)(1 << 12); head_size;
+;        offset -= (unsigned long long)(1 << 12), head_size -= (1 << 12))
+;     use(offset, (object));
+; }
+source_filename = "test.i"
+target datalayout = "e-m:o-p:32:32-f64:32:64-v64:32:64-v128:32:128-a:0:32-n32-S32"
+target triple = "thumbv7s-apple-ios5.0.0"
+
+%struct.vm_object = type { i64 }
+
+; Function Attrs: nounwind ssp
+define void @f(%struct.vm_object* %object, i64* nocapture readonly %start) local_unnamed_addr #0 !dbg !11 {
+entry:
+  tail call void @llvm.dbg.value(metadata %struct.vm_object* %object, metadata !21, metadata !DIExpression()), !dbg !27
+  tail call void @llvm.dbg.value(metadata i64* %start, metadata !22, metadata !DIExpression()), !dbg !28
+  %0 = load i64, i64* %start, align 4, !dbg !29
+  tail call void @llvm.dbg.value(metadata i64 %0, metadata !25, metadata !DIExpression()), !dbg !30
+  %offset.08 = add i64 %0, -4096
+  tail call void @llvm.dbg.value(metadata i64 %offset.08, metadata !26, metadata !DIExpression()), !dbg !31
+  ; CHECK: call void @llvm.dbg.value(metadata i64 %0, metadata !26, metadata !DIExpression(DW_OP_constu, 4096, DW_OP_minus, DW_OP_stack_value)), !dbg !30
+  tail call void @llvm.dbg.value(metadata i32 undef, metadata !23, metadata !DIExpression()), !dbg !32
+  br i1 undef, label %for.end, label %for.body.lr.ph, !dbg !32
+
+for.body.lr.ph:                                   ; preds = %entry
+  br label %for.body, !dbg !32
+
+for.body:                                         ; preds = %for.body.lr.ph, %for.body
+  %offset.010 = phi i64 [ %offset.08, %for.body.lr.ph ], [ %offset.0, %for.body ]
+  %head_size.09 = phi i32 [ undef, %for.body.lr.ph ], [ %sub2, %for.body ]
+  tail call void @llvm.dbg.value(metadata i32 %head_size.09, metadata !23, metadata !DIExpression()), !dbg !31
+  %call = tail call i32 bitcast (i32 (...)* @use to i32 (i64, %struct.vm_object*)*)(i64 %offset.010, %struct.vm_object* %object) #3, !dbg !34
+  %sub2 = add i32 %head_size.09, -4096, !dbg !37
+  %offset.0 = add i64 %offset.010, -4096
+  tail call void @llvm.dbg.value(metadata i64 %offset.0, metadata !26, metadata !DIExpression()), !dbg !30
+  ; CHECK: call void @llvm.dbg.value(metadata i64 %offset.010, metadata !26, metadata !DIExpression(DW_OP_constu, 4096, DW_OP_minus, DW_OP_stack_value)), !dbg !29
+  tail call void @llvm.dbg.value(metadata i32 %sub2, metadata !23, metadata !DIExpression()), !dbg !31
+  %tobool = icmp eq i32 %sub2, 0, !dbg !32
+  br i1 %tobool, label %for.end, label %for.body, !dbg !32, !llvm.loop !38
+
+for.end:                                          ; preds = %for.body, %entry
+  ret void, !dbg !40
+}
+
+declare i32 @use(...) local_unnamed_addr
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.value(metadata, metadata, metadata) #2
+
+attributes #0 = { nounwind ssp }
+attributes #2 = { nounwind readnone speculatable }
+attributes #3 = { nobuiltin }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!5, !6, !7, !8, !9}
+!llvm.ident = !{!10}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 6.0.0 (trunk 317434) (llvm/trunk 317437)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3)
+!1 = !DIFile(filename: "test.i", directory: "/Data/radar/31209283")
+!2 = !{}
+!3 = !{!4}
+!4 = !DIBasicType(name: "long long unsigned int", size: 64, encoding: DW_ATE_unsigned)
+!5 = !{i32 2, !"Dwarf Version", i32 2}
+!6 = !{i32 2, !"Debug Info Version", i32 3}
+!7 = !{i32 1, !"wchar_size", i32 4}
+!8 = !{i32 1, !"min_enum_size", i32 4}
+!9 = !{i32 7, !"PIC Level", i32 2}
+!10 = !{!"clang version 6.0.0 (trunk 317434) (llvm/trunk 317437)"}
+!11 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 6, type: !12, isLocal: false, isDefinition: true, scopeLine: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !20)
+!12 = !DISubroutineType(types: !13)
+!13 = !{null, !14, !19}
+!14 = !DIDerivedType(tag: DW_TAG_typedef, name: "v_t", file: !1, line: 1, baseType: !15)
+!15 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !16, size: 32)
+!16 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "v", file: !1, line: 2, size: 64, elements: !17)
+!17 = !{!18}
+!18 = !DIDerivedType(tag: DW_TAG_member, name: "p", scope: !16, file: !1, line: 3, baseType: !4, size: 64)
+!19 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !4, size: 32)
+!20 = !{!21, !22, !23, !25, !26}
+!21 = !DILocalVariable(name: "object", arg: 1, scope: !11, file: !1, line: 6, type: !14)
+!22 = !DILocalVariable(name: "start", arg: 2, scope: !11, file: !1, line: 6, type: !19)
+!23 = !DILocalVariable(name: "head_size", scope: !11, file: !1, line: 7, type: !24)
+!24 = !DIBasicType(name: "unsigned int", size: 32, encoding: DW_ATE_unsigned)
+!25 = !DILocalVariable(name: "orig_start", scope: !11, file: !1, line: 8, type: !4)
+!26 = !DILocalVariable(name: "offset", scope: !11, file: !1, line: 9, type: !4)
+!27 = !DILocation(line: 6, column: 20, scope: !11)
+!28 = !DILocation(line: 6, column: 48, scope: !11)
+!29 = !DILocation(line: 8, column: 22, scope: !11)
+!30 = !DILocation(line: 7, column: 12, scope: !11)
+!31 = !DILocation(line: 10, column: 16, scope: !11)
+!32 = !DILocation(line: 11, column: 5, scope: !33)
+!33 = distinct !DILexicalBlock(scope: !11, file: !1, line: 11, column: 5)
+!34 = !DILocation(line: 13, column: 7, scope: !35)
+!35 = distinct !DILexicalBlock(scope: !36, file: !1, line: 12, column: 75)
+!36 = distinct !DILexicalBlock(scope: !33, file: !1, line: 11, column: 5)
+!37 = !DILocation(line: 12, column: 61, scope: !36)
+!38 = distinct !{!38, !32, !39}
+!39 = !DILocation(line: 14, column: 3, scope: !33)
+!40 = !DILocation(line: 15, column: 1, scope: !11)