Move dbg.declare intrinsics when merging and replacing allocas.

Place new and update dbg.declare calls immediately after the
corresponding alloca.

Current code in replaceDbgDeclareForAlloca puts the new dbg.declare
at the end of the basic block. LLVM codegen has problems emitting
debug info in a situation when dbg.declare appears after all uses of
the variable. This usually kinda works for inlining and ASan (two
users of this function) but not for SafeStack (see the pending change
in http://reviews.llvm.org/D13178).

llvm-svn: 248769

4 files changed, 117 insertions, 7 deletions

diff --git a/llvm/lib/Transforms/IPO/Inliner.cpp b/llvm/lib/Transforms/IPO/Inliner.cpp
index 07d3633e941..14b1767721d 100644
--- a/llvm/lib/Transforms/IPO/Inliner.cpp
+++ b/llvm/lib/Transforms/IPO/Inliner.cpp
@@ -228,6 +228,14 @@ static bool InlineCallIfPossible(Pass &P, CallSite CS, InlineFunctionInfo &IFI,
       DEBUG(dbgs() << "    ***MERGED ALLOCA: " << *AI << "\n\t\tINTO: "
                    << *AvailableAlloca << '\n');
       
+      // Move affected dbg.declare calls immediately after the new alloca to
+      // avoid the situation when a dbg.declare preceeds its alloca.
+      if (auto *L = LocalAsMetadata::getIfExists(AI))
+        if (auto *MDV = MetadataAsValue::getIfExists(AI->getContext(), L))
+          for (User *U : MDV->users())
+            if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(U))
+              DDI->moveBefore(AvailableAlloca->getNextNode());
+
       AI->replaceAllUsesWith(AvailableAlloca);
 
       if (Align1 != Align2) {
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 5efa128090f..adee3f6c985 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1157,10 +1157,10 @@ bool llvm::replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
     DIExpr = Builder.createExpression(NewDIExpr);
   }
 
-  // Insert llvm.dbg.declare in the same basic block as the original alloca,
-  // and remove old llvm.dbg.declare.
-  BasicBlock *BB = AI->getParent();
-  Builder.insertDeclare(NewAllocaAddress, DIVar, DIExpr, Loc, BB);
+  // Insert llvm.dbg.declare immediately after the original alloca, and remove
+  // old llvm.dbg.declare.
+  Builder.insertDeclare(NewAllocaAddress, DIVar, DIExpr, Loc,
+                        AI->getNextNode());
   DDI->eraseFromParent();
   return true;
 }
diff --git a/llvm/test/Transforms/Inline/alloca-dbgdeclare-merge.ll b/llvm/test/Transforms/Inline/alloca-dbgdeclare-merge.ll
new file mode 100644
index 00000000000..5e10988cf50
--- /dev/null
+++ b/llvm/test/Transforms/Inline/alloca-dbgdeclare-merge.ll
@@ -0,0 +1,102 @@
+; Test that alloca merging in the inliner places dbg.declare calls immediately
+; after the merged alloca. Not at the end of the entry BB, and definitely not
+; before the alloca.
+;
+; clang -g -S -emit-llvm -Xclang -disable-llvm-optzns
+;
+;__attribute__((always_inline)) void f() {
+;  char aaa[100];
+;  aaa[10] = 1;
+;}
+;
+;__attribute__((always_inline)) void g() {
+;  char bbb[100];
+;  bbb[20] = 1;
+;}
+;
+;void h() {
+;  f();
+;  g();
+;}
+;
+; RUN: opt -always-inline -S < %s | FileCheck %s
+;
+; CHECK:      define void @h()
+; CHECK-NEXT: entry:
+; CHECK-NEXT:   %[[AI:.*]] = alloca [100 x i8]
+; CHECK-NEXT:   call void @llvm.dbg.declare(metadata [100 x i8]* %[[AI]],
+; CHECK-NEXT:   call void @llvm.dbg.declare(metadata [100 x i8]* %[[AI]],
+
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: alwaysinline nounwind uwtable
+define void @f() #0 {
+entry:
+  %aaa = alloca [100 x i8], align 16
+  call void @llvm.dbg.declare(metadata [100 x i8]* %aaa, metadata !12, metadata !17), !dbg !18
+  %arrayidx = getelementptr inbounds [100 x i8], [100 x i8]* %aaa, i64 0, i64 10, !dbg !19
+  store i8 1, i8* %arrayidx, align 2, !dbg !20
+  ret void, !dbg !21
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+; Function Attrs: alwaysinline nounwind uwtable
+define void @g() #0 {
+entry:
+  %bbb = alloca [100 x i8], align 16
+  call void @llvm.dbg.declare(metadata [100 x i8]* %bbb, metadata !22, metadata !17), !dbg !23
+  %arrayidx = getelementptr inbounds [100 x i8], [100 x i8]* %bbb, i64 0, i64 20, !dbg !24
+  store i8 1, i8* %arrayidx, align 4, !dbg !25
+  ret void, !dbg !26
+}
+
+; Function Attrs: nounwind uwtable
+define void @h() #2 {
+entry:
+  call void @f(), !dbg !27
+  call void @g(), !dbg !28
+  ret void, !dbg !29
+}
+
+attributes #0 = { alwaysinline nounwind uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone }
+attributes #2 = { nounwind uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!9, !10}
+!llvm.ident = !{!11}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.8.0 (trunk 248518) (llvm/trunk 248512)", isOptimized: false, runtimeVersion: 0, emissionKind: 1, enums: !2, subprograms: !3)
+!1 = !DIFile(filename: "../1.c", directory: "/code/llvm-git/build")
+!2 = !{}
+!3 = !{!4, !7, !8}
+!4 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 1, type: !5, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: false, function: void ()* @f, variables: !2)
+!5 = !DISubroutineType(types: !6)
+!6 = !{null}
+!7 = distinct !DISubprogram(name: "g", scope: !1, file: !1, line: 6, type: !5, isLocal: false, isDefinition: true, scopeLine: 6, isOptimized: false, function: void ()* @g, variables: !2)
+!8 = distinct !DISubprogram(name: "h", scope: !1, file: !1, line: 11, type: !5, isLocal: false, isDefinition: true, scopeLine: 11, isOptimized: false, function: void ()* @h, variables: !2)
+!9 = !{i32 2, !"Dwarf Version", i32 4}
+!10 = !{i32 2, !"Debug Info Version", i32 3}
+!11 = !{!"clang version 3.8.0 (trunk 248518) (llvm/trunk 248512)"}
+!12 = !DILocalVariable(name: "aaa", scope: !4, file: !1, line: 2, type: !13)
+!13 = !DICompositeType(tag: DW_TAG_array_type, baseType: !14, size: 800, align: 8, elements: !15)
+!14 = !DIBasicType(name: "char", size: 8, align: 8, encoding: DW_ATE_signed_char)
+!15 = !{!16}
+!16 = !DISubrange(count: 100)
+!17 = !DIExpression()
+!18 = !DILocation(line: 2, column: 8, scope: !4)
+!19 = !DILocation(line: 3, column: 3, scope: !4)
+!20 = !DILocation(line: 3, column: 11, scope: !4)
+!21 = !DILocation(line: 4, column: 1, scope: !4)
+!22 = !DILocalVariable(name: "bbb", scope: !7, file: !1, line: 7, type: !13)
+!23 = !DILocation(line: 7, column: 8, scope: !7)
+!24 = !DILocation(line: 8, column: 3, scope: !7)
+!25 = !DILocation(line: 8, column: 11, scope: !7)
+!26 = !DILocation(line: 9, column: 1, scope: !7)
+!27 = !DILocation(line: 12, column: 3, scope: !8)
+!28 = !DILocation(line: 13, column: 3, scope: !8)
+!29 = !DILocation(line: 14, column: 1, scope: !8)
diff --git a/llvm/test/Transforms/Inline/inline_dbg_declare.ll b/llvm/test/Transforms/Inline/inline_dbg_declare.ll
index f871b9a000c..481eaea7614 100644
--- a/llvm/test/Transforms/Inline/inline_dbg_declare.ll
+++ b/llvm/test/Transforms/Inline/inline_dbg_declare.ll
@@ -42,6 +42,7 @@ define void @bar(float* %dst) #0 {
 entry:
 
 ; CHECK: [[x_addr_i:%[a-zA-Z0-9.]+]] = alloca float, align 4
+; CHECK-NEXT: void @llvm.dbg.declare(metadata float* [[x_addr_i]], metadata [[m23:![0-9]+]], metadata !{{[0-9]+}}), !dbg [[m24:![0-9]+]]
 
   %dst.addr = alloca float*, align 4
   store float* %dst, float** %dst.addr, align 4
@@ -52,7 +53,6 @@ entry:
   %call = call float @foo(float %1), !dbg !22
 
 ; CHECK-NOT: call float @foo
-; CHECK: void @llvm.dbg.declare(metadata float* [[x_addr_i]], metadata [[m23:![0-9]+]], metadata !{{[0-9]+}}), !dbg [[m24:![0-9]+]]
 
   %2 = load float*, float** %dst.addr, align 4, !dbg !22
   %arrayidx1 = getelementptr inbounds float, float* %2, i32 0, !dbg !22
@@ -95,5 +95,5 @@ attributes #1 = { nounwind readnone }
 ; CHECK: [[FOO:![0-9]+]] = distinct !DISubprogram(name: "foo",
 ; CHECK: [[BAR:![0-9]+]] = distinct !DISubprogram(name: "bar",
 ; CHECK: [[m23]] = !DILocalVariable(name: "x", arg: 1, scope: [[FOO]]
-; CHECK: [[CALL_SITE:![0-9]+]] = distinct !DILocation(line: 8, column: 14, scope: [[BAR]])
-; CHECK: [[m24]] = !DILocation(line: 1, column: 17, scope: [[FOO]], inlinedAt: [[CALL_SITE]])
+; CHECK: [[m24]] = !DILocation(line: 1, column: 17, scope: [[FOO]], inlinedAt: [[CALL_SITE:![0-9]+]])
+; CHECK: [[CALL_SITE]] = distinct !DILocation(line: 8, column: 14, scope: [[BAR]])