[SafeStack] Set debug location for calls to __safestack_pointer_address.

[efriedma]

Summary

Otherwise, the debug info is incorrect. On its own, this is mostly harmless, but safe-stack also later inlines the call to __safestack_pointer_address, which leads to debug info with the wrong scope, which eventually causes an assertion failure (and incorrect debug info in release mode).

[eugenis]

lib/CodeGen/SafeStack.cpp

781

Should this be checked in module verifier?

782

In ASan we do this:

if (auto SP = F.getSubprogram())
   EntryDebugLocation = DebugLoc::get(SP->getScopeLine(), 0, SP);

Is that better? I think it will point to the opening curling bracket of the function instead of line 0.

[efriedma]

lib/CodeGen/SafeStack.cpp

781

We do, if both the caller and callee have debug info.

782

I guess so, given we're inserting this code at the beginning of the function. I'll change it.

[efriedma]

Use opening line of the function as debug location.

[efriedma]

(Please add a comment "LGTM" when you accept a patch; otherwise, Phabricator doesn't send a notification to llvm-commits.)

[eugenis]

LGTM

How interesting, "accept revision" goes to reviewers only, not to the mailing list.

lib/CodeGen/SafeStack.cpp

bool SafeStack::run() {
   if (!StaticAllocas.empty() || !DynamicAllocas.empty() ||
       !ByValArguments.empty())
     ++NumUnsafeStackFunctions; // This function has the unsafe stack.
 
   if (!StackRestorePoints.empty())
     ++NumUnsafeStackRestorePointsFunctions;
 
   IRBuilder<> IRB(&F.front(), F.begin()->getFirstInsertionPt());
+  // Calls must always have a debug location, or else inlining breaks. So
+  // we explicitly set a artificial debug location here.
+  if (DISubprogram *SP = F.getSubprogram())
+    IRB.SetCurrentDebugLocation(DebugLoc::get(SP->getScopeLine(), 0, SP));
   if (SafeStackUsePointerAddress) {
     Value *Fn = F.getParent()->getOrInsertFunction(
         "__safestack_pointer_address", StackPtrTy->getPointerTo(0));
     UnsafeStackPtr = IRB.CreateCall(Fn);
   } else {
     UnsafeStackPtr = TL.getSafeStackPointerLocation(IRB);
   }
 
   // Load the current stack pointer (we'll also use it as a base pointer).

test/Transforms/SafeStack/ARM/debug.ll

+; RUN: opt -safe-stack -safestack-use-pointer-address < %s -S | FileCheck %s
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv7-pc-linux-android"
+
+; Original C used to generate debug info:
+; char*** addr;
+; char** __safestack_pointer_address() {
+;   return *addr;
+; }
+; void Capture(char*x);
+; void f() { char c[16]; Capture(c); }
+
+; CHECK: !35 = !DILocation(line: 3, column: 11, scope: !17, inlinedAt: !36)
+; CHECK: !36 = distinct !DILocation(line: 6, scope: !27)
+
+@addr = common local_unnamed_addr global i8*** null, align 4, !dbg !0
+
+; Function Attrs: norecurse nounwind readonly safestack
+define i8** @__safestack_pointer_address() local_unnamed_addr #0 !dbg !17 {
+entry:
+  %0 = load i8***, i8**** @addr, align 4, !dbg !20, !tbaa !21
+  %1 = load i8**, i8*** %0, align 4, !dbg !25, !tbaa !21
+  ret i8** %1, !dbg !26
+}
+
+; Function Attrs: nounwind safestack
+define void @f() local_unnamed_addr #1 !dbg !27 {
+entry:
+  %c = alloca [16 x i8], align 1
+  %0 = getelementptr inbounds [16 x i8], [16 x i8]* %c, i32 0, i32 0, !dbg !35
+  call void @llvm.lifetime.start.p0i8(i64 16, i8* nonnull %0) #5, !dbg !35
+  call void @llvm.dbg.declare(metadata [16 x i8]* %c, metadata !31, metadata !DIExpression()), !dbg !36
+  call void @Capture(i8* nonnull %0) #5, !dbg !37
+  call void @llvm.lifetime.end.p0i8(i64 16, i8* nonnull %0) #5, !dbg !38
+  ret void, !dbg !38
+}
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #2
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #3
+
+declare void @Capture(i8*) local_unnamed_addr #4
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture) #2
+
+attributes #0 = { norecurse nounwind readonly safestack "correctly-rounded-divide-sqrt-fp-math"="false" "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-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="generic" "target-features"="+armv7-a,+dsp,+neon,+vfp3,-thumb-mode" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind safestack "correctly-rounded-divide-sqrt-fp-math"="false" "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-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="generic" "target-features"="+armv7-a,+dsp,+neon,+vfp3,-thumb-mode" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #2 = { argmemonly nounwind }
+attributes #3 = { nounwind readnone speculatable }
+attributes #4 = { "correctly-rounded-divide-sqrt-fp-math"="false" "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" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="generic" "target-features"="+armv7-a,+dsp,+neon,+vfp3,-thumb-mode" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #5 = { nounwind }
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!11, !12, !13, !14, !15}
+!llvm.ident = !{!16}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "addr", scope: !2, file: !6, line: 1, type: !7, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "-", directory: "/")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIFile(filename: "<stdin>", directory: "/")
+!7 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !8, size: 32)
+!8 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 32)
+!9 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 32)
+!10 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_unsigned_char)
+!11 = !{i32 2, !"Dwarf Version", i32 4}
+!12 = !{i32 2, !"Debug Info Version", i32 3}
+!13 = !{i32 1, !"wchar_size", i32 4}
+!14 = !{i32 1, !"min_enum_size", i32 4}
+!15 = !{i32 7, !"PIC Level", i32 1}
+!16 = !{!"clang"}
+!17 = distinct !DISubprogram(name: "__safestack_pointer_address", scope: !6, file: !6, line: 2, type: !18, isLocal: false, isDefinition: true, scopeLine: 2, isOptimized: true, unit: !2, retainedNodes: !4)
+!18 = !DISubroutineType(types: !19)
+!19 = !{!8}
+!20 = !DILocation(line: 3, column: 11, scope: !17)
+!21 = !{!22, !22, i64 0}
+!22 = !{!"any pointer", !23, i64 0}
+!23 = !{!"omnipotent char", !24, i64 0}
+!24 = !{!"Simple C/C++ TBAA"}
+!25 = !DILocation(line: 3, column: 10, scope: !17)
+!26 = !DILocation(line: 3, column: 3, scope: !17)
+!27 = distinct !DISubprogram(name: "f", scope: !6, file: !6, line: 6, type: !28, isLocal: false, isDefinition: true, scopeLine: 6, isOptimized: true, unit: !2, retainedNodes: !30)
+!28 = !DISubroutineType(types: !29)
+!29 = !{null}
+!30 = !{!31}
+!31 = !DILocalVariable(name: "c", scope: !27, file: !6, line: 6, type: !32)
+!32 = !DICompositeType(tag: DW_TAG_array_type, baseType: !10, size: 128, elements: !33)
+!33 = !{!34}
+!34 = !DISubrange(count: 16)
+!35 = !DILocation(line: 6, column: 12, scope: !27)
+!36 = !DILocation(line: 6, column: 17, scope: !27)
+!37 = !DILocation(line: 6, column: 24, scope: !27)
+!38 = !DILocation(line: 6, column: 36, scope: !27)