[InlineFunction] Do not propagate the callsite debug location to instructions inlined...

When a function F is inlined, InlineFunction extends the debug location of every
instruction inlined from F by adding an InlinedAt.

However, if an instruction has a 'null' debug location, InlineFunction would
propagate the callsite debug location to it. This behavior existed since
revision 210459.

Revision 210459 was originally committed specifically to workaround the lack of
debug information for instructions inlined from intrinsic functions (which are
usually declared with attributes `__always_inline__, __nodebug__`).

The problem with revision 210459 is that it doesn't make any sort of distinction
between instructions inlined from a 'nodebug' function and instructions which
are inlined from a function built with debug info. This issue may lead to
incorrect stepping in the debugger.

This patch works under the assumption that a nodebug function does not have a
DISubprogram. When a function F is inlined into another function G,
InlineFunction checks if F has debug info associated with it.

For nodebug functions, the InlineFunction logic is unchanged (i.e. it would
still propagate the callsite debugloc to the inlined instructions). Otherwise,
InlineFunction no longer propagates the callsite debug location.

Differential Revision: https://reviews.llvm.org/D27462

llvm-svn: 288895

diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index 6c02094..c9f2f72 100644 (file)
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -1350,7 +1350,7 @@ static bool allocaWouldBeStaticInEntry(const AllocaInst *AI ) {
 /// Update inlined instructions' line numbers to
 /// to encode location where these instructions are inlined.
 static void fixupLineNumbers(Function *Fn, Function::iterator FI,
-                             Instruction *TheCall) {
+                             Instruction *TheCall, bool CalleeHasDebugInfo) {
   const DebugLoc &TheCallDL = TheCall->getDebugLoc();
   if (!TheCallDL)
     return;
@@ -1374,6 +1374,8 @@ static void fixupLineNumbers(Function *Fn, Function::iterator FI,
          BI != BE; ++BI) {
       DebugLoc DL = BI->getDebugLoc();
       if (!DL) {
+        if (CalleeHasDebugInfo)
+          continue;
         // If the inlined instruction has no line number, make it look as if it
         // originates from the call location. This is important for
         // ((__always_inline__, __nodebug__)) functions which must use caller
@@ -1643,8 +1645,11 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
     if (IFI.CG)
       UpdateCallGraphAfterInlining(CS, FirstNewBlock, VMap, IFI);
 
-    // Update inlined instructions' line number information.
-    fixupLineNumbers(Caller, FirstNewBlock, TheCall);
+    // 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);
 
     // Clone existing noalias metadata if necessary.
     CloneAliasScopeMetadata(CS, VMap);

diff --git a/llvm/test/DebugInfo/Generic/inline-debug-loc.ll b/llvm/test/DebugInfo/Generic/inline-debug-loc.ll
new file mode 100644 (file)
index 0000000..032dc8e
--- /dev/null
+++ b/llvm/test/DebugInfo/Generic/inline-debug-loc.ll
@@ -0,0 +1,47 @@
+; RUN: opt -inline -S < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; Function @bar contains instruction %cmp which is not associated to any debug
+; location. This test verifies that the inliner doesn't incorrectly attribute
+; the callsite debug location to %cmp.
+
+define i32 @bar(i32 %a, i32 %b) #0 !dbg !6 {
+entry:
+  %inc = add i32 %a, 1, !dbg !8
+  %cmp = icmp slt i32 %inc, %b
+  %select = select i1 %cmp, i32 %a, i32 %b, !dbg !8
+  ret i32 %select, !dbg !8
+}
+
+
+; CHECK-LABEL: define i32 @baz(
+; CHECK: entry:
+; CHECK:   %[[INC:[a-z0-9.]+]] = add i32 %a, 1, !dbg ![[DL:[0-9]+]]
+; CHECK:   %[[CMP:[a-z0-9.]+]] = icmp slt i32 %[[INC]], %b
+; CHECK-NOT: !dbg
+; CHECK:   %[[SELECT:[a-z0-9.]+]] = select i1 %[[CMP]], i32 %a, i32 %b, !dbg ![[DL]]
+;
+; ![[DL]] = !DILocation(line: 3, scope: !{{.*}}, inlinedAt: {{.*}})
+
+define i32 @baz(i32 %a, i32 %b) !dbg !9 {
+entry:
+  %call = tail call i32 @bar(i32 %a, i32 %b), !dbg !10
+  ret i32 %call, !dbg !10
+}
+
+attributes #0 = { alwaysinline }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, isOptimized: true, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2)
+!1 = !DIFile(filename: "test.c", directory: "")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!6 = distinct !DISubprogram(name: "bar", scope: !1, file: !1, line: 2, type: !7, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !2)
+!7 = !DISubroutineType(types: !2)
+!8 = !DILocation(line: 3, scope: !6)
+!9 = distinct !DISubprogram(name: "baz", scope: !1, file: !1, line: 11, type: !7, isLocal: false, isDefinition: true, scopeLine: 11, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !2)
+!10 = !DILocation(line: 12, scope: !9)