Implement salavageDebugInfo functionality for SelectionDAG.

Similar to how llvm::salvagDebugInfo hooks into InstCombine, this adds
a hook that can be invoked before an SDNode that is associated with an
SDDbgValue is erased to capture the effect of the deleted node in a
DIExpression.

The motivating example is an SDDebugValue attached to an ADD operation
that gets folded into a LOAD+OFFSET operation.

rdar://problem/32121503

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@316525 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/SelectionDAG.h b/include/llvm/CodeGen/SelectionDAG.h
index 61ae1c91073cba89b2e2c49c642b408d5dd9eb93..460e58c9dea0ef651d874512f10e68f3b9547d94 100644 (file)
--- a/include/llvm/CodeGen/SelectionDAG.h
+++ b/include/llvm/CodeGen/SelectionDAG.h
@@ -1286,6 +1286,10 @@ public:
     return DbgInfo->ByvalParmDbgEnd();
   }
 
+  /// To be invoked on an SDNode that is slated to be erased. This
+  /// function mirrors \c llvm::salvageDebugInfo.
+  void salvageDebugInfo(SDNode &N);
+
   void dump() const;
 
   /// Create a stack temporary, suitable for holding the specified value type.

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index f712862f184ccbc5eec62215689d461f54d0c660..dd5e1e5a3ee5258c73010a65f505bf6869d52bc7 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -6978,6 +6978,40 @@ SDDbgValue *SelectionDAG::getFrameIndexDbgValue(DIVariable *Var,
   return new (DbgInfo->getAlloc()) SDDbgValue(Var, Expr, FI, DL, O);
 }
 
+void SelectionDAG::salvageDebugInfo(SDNode &N) {
+  if (!N.getHasDebugValue())
+    return;
+  for (auto DV : GetDbgValues(&N)) {
+    if (DV->isInvalidated())
+      continue;
+    switch (N.getOpcode()) {
+    default:
+      break;
+    case ISD::ADD:
+      SDValue N0 = N.getOperand(0);
+      SDValue N1 = N.getOperand(1);
+      if (!isConstantIntBuildVectorOrConstantInt(N0) &&
+          isConstantIntBuildVectorOrConstantInt(N1)) {
+        uint64_t Offset = N.getConstantOperandVal(1);
+        // Rewrite an ADD constant node 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.
+        auto *DIExpr = DV->getExpression();
+        DIExpr = DIExpression::prepend(DIExpr, DIExpression::NoDeref, Offset,
+                                       DIExpression::WithStackValue);
+        SDDbgValue *Clone =
+            getDbgValue(DV->getVariable(), DIExpr, N0.getNode(), N0.getResNo(),
+                        DV->isIndirect(), DV->getDebugLoc(), DV->getOrder());
+        DV->setIsInvalidated();
+        AddDbgValue(Clone, N0.getNode(), false);
+        DEBUG(dbgs() << "SALVAGE: Rewriting"; N0.getNode()->dumprFull(this);
+              dbgs() << " into " << *DIExpr << '\n');
+      }
+    }
+  }
+}
+
 namespace {
 
 /// RAUWUpdateListener - Helper for ReplaceAllUsesWith - When the node

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 5311ef437e9254698f99b40c9cecc4f0f0f57ebe..4c4d196427e2ff5372baa200cb57f46b689251ea 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -3550,6 +3550,7 @@ void SelectionDAGISel::SelectCodeCommon(SDNode *NodeToMatch,
                "NodeToMatch was removed partway through selection");
         SelectionDAG::DAGNodeDeletedListener NDL(*CurDAG, [&](SDNode *N,
                                                               SDNode *E) {
+          CurDAG->salvageDebugInfo(*N);
           auto &Chain = ChainNodesMatched;
           assert((!E || !is_contained(Chain, N)) &&
                  "Chain node replaced during MorphNode");

diff --git a/test/DebugInfo/X86/sdag-salvage-add.ll b/test/DebugInfo/X86/sdag-salvage-add.ll
new file mode 100644 (file)
index 0000000..827aed6
--- /dev/null
+++ b/test/DebugInfo/X86/sdag-salvage-add.ll
@@ -0,0 +1,110 @@
+; RUN: llc -mtriple=x86_64-unknown-unknown -stop-before livedebugvalues %s -o - \
+; RUN:   | FileCheck %s
+;
+; Generated at -O1 from:
+; typedef struct {
+;   unsigned long long c;
+; } S1;
+; struct S3 {
+;   unsigned long long packed;
+; };
+; struct S6 {
+;   struct S0 *b;
+; };
+; void f(struct S3 *a3)
+; {
+;   struct S4 *s4 = (struct S4 *)(a3->packed + 0x1000UL);
+;   struct S6 *myVar = (struct S6 *)s4;
+;   struct S0 *b = myVar->b;
+;   use(b);
+; }
+;
+; The debug info is attached to the ADD 4096 operation, which doesn't survive
+; instruction selection as it is folded into the load.
+;
+; CHECK:   ![[S4:.*]] = !DILocalVariable(name: "s4", 
+; CHECK:   ![[MYVAR:.*]] = !DILocalVariable(name: "myVar", 
+; CHECK:      DBG_VALUE debug-use %rax, debug-use _, ![[MYVAR]],
+; CHECK-SAME:           !DIExpression(DW_OP_plus_uconst, 4096, DW_OP_stack_value)
+; CHECK-NEXT: DBG_VALUE debug-use %rax, debug-use _, ![[S4]],
+; CHECK-SAME:           !DIExpression(DW_OP_plus_uconst, 4096, DW_OP_stack_value)
+; CHECK-NEXT: %rdi = MOV64rm killed %rax, 1, _, 4096, _,
+
+source_filename = "test.c"
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.13.0"
+
+%struct.S3 = type { i64 }
+%struct.S4 = type opaque
+%struct.S0 = type opaque
+
+; Function Attrs: noinline nounwind ssp uwtable
+define void @f(%struct.S3* nocapture readonly %a3) local_unnamed_addr #0 !dbg !6 {
+entry:
+  tail call void @llvm.dbg.value(metadata %struct.S3* %a3, metadata !15, metadata !DIExpression()), !dbg !30
+  %packed = getelementptr inbounds %struct.S3, %struct.S3* %a3, i64 0, i32 0, !dbg !31
+  %0 = load i64, i64* %packed, align 8, !dbg !31
+  %add = add i64 %0, 4096, !dbg !37
+  %1 = inttoptr i64 %add to %struct.S4*, !dbg !38
+  tail call void @llvm.dbg.value(metadata %struct.S4* %1, metadata !16, metadata !DIExpression()), !dbg !39
+  tail call void @llvm.dbg.value(metadata %struct.S4* %1, metadata !17, metadata !DIExpression()), !dbg !40
+  %b1 = bitcast %struct.S4* %1 to %struct.S0**, !dbg !41
+  %2 = load %struct.S0*, %struct.S0** %b1, align 8, !dbg !41
+  tail call void @llvm.dbg.value(metadata %struct.S0* %2, metadata !24, metadata !DIExpression()), !dbg !45
+  %call = tail call i32 (%struct.S0*, ...) bitcast (i32 (...)* @use to i32 (%struct.S0*, ...)*)(%struct.S0* %2) #3, !dbg !46
+  ret void, !dbg !47
+}
+
+declare i32 @use(...) local_unnamed_addr
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.value(metadata, metadata, metadata) #2
+
+attributes #0 = { noinline nounwind ssp uwtable }
+attributes #2 = { nounwind readnone speculatable }
+attributes #3 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!25, !26, !27, !28}
+!llvm.ident = !{!29}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 6.0.0 (trunk 316467) (llvm/trunk 316466)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3)
+!1 = !DIFile(filename: "test.c", directory: "/")
+!2 = !{}
+!3 = !{!4, !18}
+!4 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !5, size: 64)
+!5 = !DICompositeType(tag: DW_TAG_structure_type, name: "S4", scope: !6, file: !1, line: 20, flags: DIFlagFwdDecl)
+!6 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 18, type: !7, isLocal: false, isDefinition: true, scopeLine: 19, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !14)
+!7 = !DISubroutineType(types: !8)
+!8 = !{null, !9}
+!9 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 64)
+!10 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "S3", file: !1, line: 5, size: 64, elements: !11)
+!11 = !{!12}
+!12 = !DIDerivedType(tag: DW_TAG_member, name: "packed", scope: !10, file: !1, line: 6, baseType: !13, size: 64)
+!13 = !DIBasicType(name: "long long unsigned int", size: 64, encoding: DW_ATE_unsigned)
+!14 = !{!15, !16, !17, !24}
+!15 = !DILocalVariable(name: "a3", arg: 1, scope: !6, file: !1, line: 18, type: !9)
+!16 = !DILocalVariable(name: "s4", scope: !6, file: !1, line: 20, type: !4)
+!17 = !DILocalVariable(name: "myVar", scope: !6, file: !1, line: 21, type: !18)
+!18 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !19, size: 64)
+!19 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "S6", file: !1, line: 8, size: 64, elements: !20)
+!20 = !{!21}
+!21 = !DIDerivedType(tag: DW_TAG_member, name: "b", scope: !19, file: !1, line: 9, baseType: !22, size: 64)
+!22 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !23, size: 64)
+!23 = !DICompositeType(tag: DW_TAG_structure_type, name: "S0", file: !1, line: 4, flags: DIFlagFwdDecl)
+!24 = !DILocalVariable(name: "b", scope: !6, file: !1, line: 22, type: !22)
+!25 = !{i32 2, !"Dwarf Version", i32 4}
+!26 = !{i32 2, !"Debug Info Version", i32 3}
+!27 = !{i32 1, !"wchar_size", i32 4}
+!28 = !{i32 7, !"PIC Level", i32 2}
+!29 = !{!"clang version 6.0.0 (trunk 316467) (llvm/trunk 316466)"}
+!30 = !DILocation(line: 18, column: 14, scope: !6)
+!31 = !DILocation(line: 20, column: 37, scope: !6)
+!37 = !DILocation(line: 20, column: 44, scope: !6)
+!38 = !DILocation(line: 20, column: 19, scope: !6)
+!39 = !DILocation(line: 20, column: 14, scope: !6)
+!40 = !DILocation(line: 21, column: 14, scope: !6)
+!41 = !DILocation(line: 22, column: 25, scope: !6)
+!45 = !DILocation(line: 22, column: 14, scope: !6)
+!46 = !DILocation(line: 23, column: 3, scope: !6)
+!47 = !DILocation(line: 24, column: 1, scope: !6)