[PATCH] D16061: [Utils] Insert DW_OP_bit_piece when only describing part of the variable

[Keno Fischer via llvm-commits]

loladiro created this revision.
loladiro added a reviewer: aprantl.
loladiro added a subscriber: llvm-commits.
loladiro set the repository for this revision to rL LLVM.

The dbg.declare -> dbg.value conversion looks through any zext/sext to find a value to describe the variable (in the expectation that those zext/sext instruction will go away later). However, those values do not cover the entire variable and thus need a DW_OP_bit_piece.

Repository:
  rL LLVM

http://reviews.llvm.org/D16061

Files:
  lib/Transforms/Utils/Local.cpp
  test/Transforms/Util/split-bit-piece.ll

Index: test/Transforms/Util/split-bit-piece.ll
===================================================================
--- /dev/null
+++ test/Transforms/Util/split-bit-piece.ll
@@ -0,0 +1,45 @@
+; Checks that SROA inserts a proper bit piece expression if it only describes
+; part of a variable
+; RUN: opt -S -sroa %s | FileCheck %s
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #0
+
+; Function Attrs: nounwind uwtable
+define hidden void @_ZN6__tsan9FastState14SetHistorySizeEi(i32 %hs) #1 align 2 {
+entry:
+  %hs.addr = alloca i32, align 4
+  %v1 = alloca i64, align 8
+  %v2 = alloca i64, align 8
+  store i32 %hs, i32* %hs.addr, align 4
+; CHECK: call void @llvm.dbg.value({{[^,]*}}, i64 0, metadata !{{[0-9]+}}, metadata ![[EXPR:[0-9]+]])
+; CHECK: ![[EXPR]] = !DIExpression(DW_OP_bit_piece, 0
+  call void @llvm.dbg.declare(metadata i64* %v1, metadata !9, metadata !12), !dbg !13
+  %0 = load i32, i32* %hs.addr, align 4
+  %conv = sext i32 %0 to i64
+  store i64 %conv, i64* %v1, align 8
+  %1 = load i64, i64* %v2, align 8
+  unreachable
+}
+
+attributes #0 = { nounwind readnone }
+attributes #1 = { nounwind uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!7}
+!llvm.ident = !{!8}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.8.0 (trunk 256979) (llvm/trunk 257107)", isOptimized: false, runtimeVersion: 0, emissionKind: 1, retainedTypes: !2)
+!1 = !DIFile(filename: "tsan_shadow_test.cc", directory: "/tmp")
+!2 = !{!3, !5}
+!3 = !DICompositeType(tag: DW_TAG_class_type, name: "FastState", file: !4, line: 91, size: 64, align: 64, identifier: "_ZTSN6__tsan9FastStateE")
+!4 = !DIFile(filename: "/mnt/extra/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_rtl.h", directory: "/tmp")
+!5 = distinct !DIDerivedType(tag: DW_TAG_typedef, name: "u64", line: 78, baseType: !6)
+!6 = !DIBasicType(name: "long long unsigned int", size: 64, align: 64, encoding: DW_ATE_unsigned)
+!7 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = !{!"clang version 3.8.0 (trunk 256979) (llvm/trunk 257107)"}
+!9 = !DILocalVariable(name: "v1", scope: !10, file: !4, line: 136, type: !5)
+!10 = distinct !DILexicalBlock(scope: !11, file: !4, line: 136, column: 5)
+!11 = distinct !DISubprogram(name: "SetHistorySize", linkageName: "_ZN6__tsan9FastState14SetHistorySizeEi", scope: !"_ZTSN6__tsan9FastStateE", file: !4, line: 135, isLocal: false, isDefinition: true, scopeLine: 135, flags: DIFlagPrototyped, isOptimized: false)
+!12 = !DIExpression()
+!13 = !DILocation(line: 136, column: 5, scope: !10)
Index: lib/Transforms/Utils/Local.cpp
===================================================================
--- lib/Transforms/Utils/Local.cpp
+++ lib/Transforms/Utils/Local.cpp
@@ -1051,9 +1051,18 @@
     ExtendedArg = dyn_cast<Argument>(ZExt->getOperand(0));
   if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
     ExtendedArg = dyn_cast<Argument>(SExt->getOperand(0));
-  if (ExtendedArg)
-    Builder.insertDbgValueIntrinsic(ExtendedArg, 0, DIVar, DIExpr,
+  if (ExtendedArg) {
+    // We're now only describing a subset of the variable
+    SmallVector<uint64_t, 3> NewDIExpr;
+    NewDIExpr.append(DIExpr->elements_begin(), DIExpr->elements_end());
+    NewDIExpr.push_back(dwarf::DW_OP_bit_piece);
+    NewDIExpr.push_back(0); //Offset
+    const DataLayout &DL = DDI->getModule()->getDataLayout();
+    NewDIExpr.push_back(DL.getTypeSizeInBits(ExtendedArg->getType())); // Size
+    Builder.insertDbgValueIntrinsic(ExtendedArg, 0, DIVar,
+                                    Builder.createExpression(NewDIExpr),
                                     DDI->getDebugLoc(), SI);
+  }
   else
     Builder.insertDbgValueIntrinsic(SI->getOperand(0), 0, DIVar, DIExpr,
                                     DDI->getDebugLoc(), SI);


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D16061.44474.patch
Type: text/x-patch
Size: 4128 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20160111/e1ba2d84/attachment.bin>