Strip debug info when inlining into a nodebug function.

The LLVM backend cannot produce any debug info for an llvm::Function
without a DISubprogram attachment. When inlining a debug-info-carrying
function into a nodebug function, there is therefore no reason to keep
any debug info intrinsic calls or debug locations on the instructions.

This fixes a problem discovered in PR32042.

rdar://problem/30679307

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296488 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Utils/InlineFunction.cpp

@@ -1343,22 +1343,26 @@ static bool allocaWouldBeStaticInEntry(const AllocaInst *AI ) {
   return isa<Constant>(AI->getArraySize()) && !AI->isUsedWithInAlloca();
 }
 
-/// Update inlined instructions' line numbers to
-/// to encode location where these instructions are inlined.
-static void fixupLineNumbers(Function *Fn, Function::iterator FI,
-                             Instruction *TheCall, bool CalleeHasDebugInfo) {
+/// Update inlined instructions' line numbers to to encode location where these
+/// instructions are inlined.  Also strip all debug intrinsics that were inlined
+/// into a nodebug function; there is no debug info the backend could produce
+/// for a function without a DISubprogram attachment.
+static void fixupDebugInfo(Function *Fn, Function::iterator FI,
+                           Instruction *TheCall, bool CalleeHasDebugInfo) {
+  bool CallerHasDebugInfo = Fn->getSubprogram();
+  bool StripDebugInfo = !CallerHasDebugInfo && CalleeHasDebugInfo;
+  SmallVector<DbgInfoIntrinsic *, 8> IntrinsicsToErase;
   const DebugLoc &TheCallDL = TheCall->getDebugLoc();
-  if (!TheCallDL)
-    return;
 
   auto &Ctx = Fn->getContext();
-  DILocation *InlinedAtNode = TheCallDL;
+  DILocation *InlinedAtNode = nullptr;
 
   // Create a unique call site, not to be confused with any other call from the
   // same location.
-  InlinedAtNode = DILocation::getDistinct(
-      Ctx, InlinedAtNode->getLine(), InlinedAtNode->getColumn(),
-      InlinedAtNode->getScope(), InlinedAtNode->getInlinedAt());
+  if (TheCallDL)
+    InlinedAtNode = DILocation::getDistinct(
+        Ctx, TheCallDL->getLine(), TheCallDL->getColumn(),
+        TheCallDL->getScope(), TheCallDL->getInlinedAt());
 
   // Cache the inlined-at nodes as they're built so they are reused, without
   // this every instruction's inlined-at chain would become distinct from each
@@ -1368,6 +1372,17 @@ static void fixupLineNumbers(Function *Fn, Function::iterator FI,
   for (; FI != Fn->end(); ++FI) {
     for (BasicBlock::iterator BI = FI->begin(), BE = FI->end();
          BI != BE; ++BI) {
+      if (StripDebugInfo) {
+        // Inlining into a nodebug function.
+        if (auto *DI = dyn_cast<DbgInfoIntrinsic>(BI))
+          // Mark dead debug intrinsics for deletion.
+          IntrinsicsToErase.push_back(DI);
+        else
+          // Remove the dangling debug location.
+          BI->setDebugLoc(DebugLoc());
+        continue;
+      }
+
       if (DebugLoc DL = BI->getDebugLoc()) {
         BI->setDebugLoc(
             updateInlinedAtInfo(DL, InlinedAtNode, BI->getContext(), IANodes));
@@ -1390,6 +1405,9 @@ static void fixupLineNumbers(Function *Fn, Function::iterator FI,
       BI->setDebugLoc(TheCallDL);
     }
   }
+
+  for (auto *DI : IntrinsicsToErase)
+    DI->eraseFromParent();
 }
 /// Update the block frequencies of the caller after a callee has been inlined.
 ///
@@ -1710,8 +1728,8 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
     // For 'nodebug' functions, the associated DISubprogram is always null.
     // Conservatively avoid propagating the callsite debug location to
     // instructions inlined from a function whose DISubprogram is not null.
-    fixupLineNumbers(Caller, FirstNewBlock, TheCall,
-                     CalledFunc->getSubprogram() != nullptr);
+    fixupDebugInfo(Caller, FirstNewBlock, TheCall,
+                   CalledFunc->getSubprogram() != nullptr);
 
     // Clone existing noalias metadata if necessary.
     CloneAliasScopeMetadata(CS, VMap);

test/Transforms/Inline/local-as-metadata-undominated-use.ll

@@ -16,14 +16,14 @@ entry:
 }
 
 ; CHECK-LABEL: define i32 @caller(
-define i32 @caller(i32 %i) {
+define i32 @caller(i32 %i) !dbg !3 {
 ; CHECK-NEXT: entry:
 entry:
 ; Although the inliner shouldn't crash, it can't be expected to get the
 ; "correct" SSA value since its assumptions have been violated.
 ; CHECK-NEXT:   tail call void @llvm.dbg.value(metadata ![[EMPTY:[0-9]+]],
 ; CHECK-NEXT:   %{{.*}} = add nsw
-  %call = tail call i32 @foo(i32 %i)
+  %call = tail call i32 @foo(i32 %i), !dbg !14
   ret i32 %call
 }
 
@@ -34,9 +34,9 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
 
 !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.9.0 (trunk 265634) (llvm/trunk 265637)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
 !1 = !DIFile(filename: "t.c", directory: "/path/to/tests")
-
 ; CHECK: ![[EMPTY]] = !{}
 !2 = !{}
+!3 = distinct !DISubprogram(name: "caller", scope: !1, file: !1, line: 3, type: !5, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: true, unit: !0)
 !4 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 2, type: !5, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: true, unit: !0)
 !5 = !DISubroutineType(types: !6)
 !6 = !{!7, !7}
@@ -47,3 +47,4 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
 !11 = !DILocation(line: 2, column: 13, scope: !4)
 !12 = !DILocation(line: 2, column: 27, scope: !4)
 !13 = !DILocation(line: 2, column: 18, scope: !4)
+!14 = !DILocation(line: 3, scope: !3)

test/Transforms/Inline/nodebug.ll

@@ -0,0 +1,36 @@
+; RUN: opt -inline -S -o - < %s | FileCheck %s
+; Check that debug info is stripped when inlining into a nodebug function.
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
+
+define void @foo() !dbg !2 {
+entry:
+  %a = alloca i32
+  call void @llvm.dbg.value(metadata i32 0, i64 0, metadata !3, metadata !DIExpression()), !dbg !6
+  store i32 0, i32* %a, !dbg !6
+  ret void, !dbg !6
+}
+
+; CHECK: define void @bar()
+define void @bar() {
+; CHECK-NEXT: entry
+entry:
+; CHECK-NEXT: alloca i32
+; CHECK-NOT: dbg
+; CHECK: ret void
+  call void @foo()
+  ret void
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!7, !8}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang", emissionKind: FullDebug)
+!1 = !DIFile(filename: "x.c", directory: "/")
+!2 = distinct !DISubprogram(name: "foo", scope: !0, isDefinition: true, unit: !0)
+!3 = !DILocalVariable(name: "a", arg: 1, scope: !2, file: !1, line: 1, type: !5)
+!5 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!6 = !DILocation(line: 1, scope: !2)
+!7 = !{i32 2, !"Dwarf Version", i32 4}
+!8 = !{i32 1, !"Debug Info Version", i32 3}