From cfcc1f1c64e267f94119cca6cb1021561e7ef125 Mon Sep 17 00:00:00 2001
From: Adrian Prantl <aprantl@apple.com>
Date: Mon, 13 Nov 2017 21:24:54 +0000
Subject: [PATCH] Fix an assertion in SelectionDAG::transferDbgValues() when
 transferring debug info describing the lower bits of an extended SDNode.

rdar://problem/35504722

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@318086 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 27 ++++++++++++++++-----------
 test/DebugInfo/ARM/sdag-split-arg1.ll     | 28 ++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 11 deletions(-)
 create mode 100644 test/DebugInfo/ARM/sdag-split-arg1.ll

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 1c4589ef14f..1ed982d6bac 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -7042,18 +7042,23 @@ void SelectionDAG::transferDbgValues(SDValue From, SDValue To,
     auto *Expr = Dbg->getExpression();
     // If a fragment is requested, update the expression.
     if (SizeInBits) {
-      auto Fragment = DIExpression::createFragmentExpression(
-          Dbg->getExpression(), OffsetInBits, SizeInBits);
-      if (Fragment)
-        Expr = *Fragment;
-    }
-    // Clone the SbgValue unless the fragment creation failed.
-    if (!SizeInBits || (SizeInBits && Expr)) {
-      SDDbgValue *Clone =
-          getDbgValue(Var, Expr, ToNode, To.getResNo(), Dbg->isIndirect(),
-                      Dbg->getDebugLoc(), Dbg->getOrder());
-      ClonedDVs.push_back(Clone);
+      // When splitting a larger (e.g., sign-extended) value whose
+      // lower bits are described with an SDDbgValue, do not attempt
+      // to transfer the SDDbgValue to the upper bits.
+      if (auto FI = Expr->getFragmentInfo())
+        if (OffsetInBits + SizeInBits > FI->SizeInBits)
+          continue;
+      auto Fragment = DIExpression::createFragmentExpression(Expr, OffsetInBits,
+                                                             SizeInBits);
+      if (!Fragment)
+        continue;
+      Expr = *Fragment;
     }
+    // Clone the SDDbgValue and move it to To.
+    SDDbgValue *Clone =
+        getDbgValue(Var, Expr, ToNode, To.getResNo(), Dbg->isIndirect(),
+                    Dbg->getDebugLoc(), Dbg->getOrder());
+    ClonedDVs.push_back(Clone);
     Dbg->setIsInvalidated();
   }
 
diff --git a/test/DebugInfo/ARM/sdag-split-arg1.ll b/test/DebugInfo/ARM/sdag-split-arg1.ll
new file mode 100644
index 00000000000..c39083afd08
--- /dev/null
+++ b/test/DebugInfo/ARM/sdag-split-arg1.ll
@@ -0,0 +1,28 @@
+; RUN: llc -filetype=asm %s -o -  -stop-after=livedebugvalues | FileCheck %s
+; This tests that transferring debug info describing the lower bits of
+; an extended SDNode works.
+target triple = "thumbv6m-apple-unknown-macho"
+define arm_aapcscc i64 @f(double %a) !dbg !5 {
+entry:
+  %0 = bitcast double %a to i64
+  %extract.t84 = trunc i64 %0 to i32
+  tail call void @llvm.dbg.value(metadata i32 %extract.t84, metadata !8, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 32)), !dbg !12
+  ; CHECK: DBG_VALUE debug-use %r0, debug-use _, !6, !DIExpression(DW_OP_LLVM_fragment, 0, 32)
+  %r.sroa.0.0.insert.ext35 = zext i32 %extract.t84 to i64
+  ret i64 %r.sroa.0.0.insert.ext35
+}
+
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "LLVM", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !2)
+!1 = !DIFile(filename: "f.c", directory: "/")
+!2 = !{}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 29, type: !7, isLocal: false, isDefinition: true, scopeLine: 30, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !2)
+!7 = !DISubroutineType(types: !2)
+!8 = !DILocalVariable(name: "r", scope: !5, file: !1, line: 37, type: !11)
+!11 = distinct !DICompositeType(tag: DW_TAG_union_type, file: !1, line: 33, size: 64, elements: !2)
+!12 = !DILocation(line: 37, column: 12, scope: !5)
-- 
2.11.0