PR15662: Optimized debug info produces out of order function parameters

When a function is inlined we lazily construct the variables
representing the function's parameters. After that, we add any remaining
unused parameters.

If the function doesn't use all the parameters, or uses them out of
order, then the DWARF would produce them in that order, producing a
parameter order that doesn't match the source.

This fix causes us to always keep the arg variables at the start of the
variable list & in the original order from the source.

llvm-svn: 183297

2 files changed, 104 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index e761afe97ab..f7337d7bd45 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1626,9 +1626,37 @@ void DwarfDebug::beginFunction(const MachineFunction *MF) {
 }
 
 void DwarfDebug::addScopeVariable(LexicalScope *LS, DbgVariable *Var) {
-//  SmallVector<DbgVariable *, 8> &Vars = ScopeVariables.lookup(LS);
-  ScopeVariables[LS].push_back(Var);
-//  Vars.push_back(Var);
+  SmallVectorImpl<DbgVariable *> &Vars = ScopeVariables[LS];
+  DIVariable DV = Var->getVariable();
+  if (DV.getTag() == dwarf::DW_TAG_arg_variable) {
+    DISubprogram Ctxt(DV.getContext());
+    DIArray Variables = Ctxt.getVariables();
+    // If the variable is a parameter (arg_variable) and this is an optimized
+    // build (the subprogram has a 'variables' list) make sure we keep the
+    // parameters in order. Otherwise we would produce an incorrect function
+    // type with parameters out of order if function parameters were used out of
+    // order or unused (see the call to addScopeVariable in endFunction where
+    // the remaining unused variables (including parameters) are added).
+    if (unsigned NumVariables = Variables.getNumElements()) {
+      // Keep the parameters at the start of the variables list. Search through
+      // current variable list (Vars) and the full function variable list in
+      // lock-step looking for this parameter in the full list to find the
+      // insertion point.
+      SmallVectorImpl<DbgVariable *>::iterator I = Vars.begin();
+      unsigned j = 0;
+      while (I != Vars.end() && j != NumVariables &&
+             Variables.getElement(j) != DV &&
+             (*I)->getVariable().getTag() == dwarf::DW_TAG_arg_variable) {
+        if (Variables.getElement(j) == (*I)->getVariable())
+          ++I;
+        ++j;
+      }
+      Vars.insert(I, Var);
+      return;
+    }
+  }
+
+  Vars.push_back(Var);
 }
 
 // Gather and emit post-function debug information.
diff --git a/llvm/test/DebugInfo/inlined-arguments.ll b/llvm/test/DebugInfo/inlined-arguments.ll
new file mode 100644
index 00000000000..d3ece100634
--- /dev/null
+++ b/llvm/test/DebugInfo/inlined-arguments.ll
@@ -0,0 +1,73 @@
+; RUN: llc -filetype=obj < %s > %t
+; RUN: llvm-dwarfdump %t | FileCheck %s
+
+; IR generated from clang -O -g with the following source
+;
+; void f1(int x, int y);
+; void f3(int line);
+; void f2() {
+;   f1(1, 2);
+; }
+; void f1(int x, int y) {
+;   f3(y);
+; }
+
+; CHECK: DW_AT_name{{.*}}"f1"
+; CHECK: DW_TAG_formal_parameter
+; CHECK-NEXT: DW_AT_name{{.*}}"x"
+; CHECK: DW_TAG_formal_parameter
+; CHECK-NEXT: DW_AT_name{{.*}}"y"
+
+; Function Attrs: uwtable
+define void @_Z2f2v() #0 {
+  tail call void @llvm.dbg.value(metadata !15, i64 0, metadata !16), !dbg !18
+  tail call void @llvm.dbg.value(metadata !19, i64 0, metadata !20), !dbg !18
+  tail call void @_Z2f3i(i32 2), !dbg !21
+  ret void, !dbg !22
+}
+
+; Function Attrs: uwtable
+define void @_Z2f1ii(i32 %x, i32 %y) #0 {
+  tail call void @llvm.dbg.value(metadata !{i32 %x}, i64 0, metadata !13), !dbg !23
+  tail call void @llvm.dbg.value(metadata !{i32 %y}, i64 0, metadata !14), !dbg !23
+  tail call void @_Z2f3i(i32 %y), !dbg !24
+  ret void, !dbg !25
+}
+
+declare void @_Z2f3i(i32) #1
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata) #2
+
+attributes #0 = { uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-frame-pointer-elim-non-leaf"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-frame-pointer-elim-non-leaf"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #2 = { nounwind readnone }
+
+!llvm.dbg.cu = !{!0}
+
+!0 = metadata !{i32 786449, metadata !1, i32 4, metadata !"clang version 3.4 ", i1 true, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !""} ; [ DW_TAG_compile_unit ] [/usr/local/google/home/blaikie/dev/scratch/exp.cpp] [DW_LANG_C_plus_plus]
+!1 = metadata !{metadata !"exp.cpp", metadata !"/usr/local/google/home/blaikie/dev/scratch"}
+!2 = metadata !{i32 0}
+!3 = metadata !{metadata !4, metadata !8}
+!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f2", metadata !"f2", metadata !"_Z2f2v", i32 3, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 true, void ()* @_Z2f2v, null, null, metadata !2, i32 3} ; [ DW_TAG_subprogram ] [line 3] [def] [f2]
+!5 = metadata !{i32 786473, metadata !1}          ; [ DW_TAG_file_type ] [/usr/local/google/home/blaikie/dev/scratch/exp.cpp]
+!6 = metadata !{i32 786453, i32 0, i32 0, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !7, i32 0, i32 0} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = metadata !{null}
+!8 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f1", metadata !"f1", metadata !"_Z2f1ii", i32 6, metadata !9, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 true, void (i32, i32)* @_Z2f1ii, null, null, metadata !12, i32 6} ; [ DW_TAG_subprogram ] [line 6] [def] [f1]
+!9 = metadata !{i32 786453, i32 0, i32 0, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !10, i32 0, i32 0} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!10 = metadata !{null, metadata !11, metadata !11}
+!11 = metadata !{i32 786468, null, null, metadata !"int", i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
+!12 = metadata !{metadata !13, metadata !14}
+!13 = metadata !{i32 786689, metadata !8, metadata !"x", metadata !5, i32 16777222, metadata !11, i32 0, i32 0} ; [ DW_TAG_arg_variable ] [x] [line 6]
+!14 = metadata !{i32 786689, metadata !8, metadata !"y", metadata !5, i32 33554438, metadata !11, i32 0, i32 0} ; [ DW_TAG_arg_variable ] [y] [line 6]
+!15 = metadata !{i32 undef}
+!16 = metadata !{i32 786689, metadata !8, metadata !"x", metadata !5, i32 16777222, metadata !11, i32 0, metadata !17} ; [ DW_TAG_arg_variable ] [x] [line 6]
+!17 = metadata !{i32 4, i32 0, metadata !4, null}
+!18 = metadata !{i32 6, i32 0, metadata !8, metadata !17}
+!19 = metadata !{i32 2}
+!20 = metadata !{i32 786689, metadata !8, metadata !"y", metadata !5, i32 33554438, metadata !11, i32 0, metadata !17} ; [ DW_TAG_arg_variable ] [y] [line 6]
+!21 = metadata !{i32 7, i32 0, metadata !8, metadata !17}
+!22 = metadata !{i32 5, i32 0, metadata !4, null}
+!23 = metadata !{i32 6, i32 0, metadata !8, null}
+!24 = metadata !{i32 7, i32 0, metadata !8, null}
+!25 = metadata !{i32 8, i32 0, metadata !8, null} ; [ DW_TAG_imported_declaration ]