[PseudoProbe] Do not force the calliste debug loc to inlined probes from __nodebug__ functions.

For pseudo probes we would like to keep their original dwarf discriminator (either a zero or null) until the first FS-discriminator pass. The inliner is a violation of that, given that it assigns inlinee instructions with no debug info with the that of the callsite. This is being disabled in this patch.

Reviewed By: wenlei

Differential Revision: https://reviews.llvm.org/D151568

Author: htyu

llvm/lib/Transforms/Utils/InlineFunction.cpp

@@ -1636,6 +1636,12 @@ static void fixupLineNumbers(Function *Fn, Function::iterator FI,
         if (allocaWouldBeStaticInEntry(AI))
           continue;
 
+      // Do not force a debug loc for pseudo probes, since they do not need to
+      // be debuggable, and also they are expected to have a zero/null dwarf
+      // discriminator at this point which could be violated otherwise.
+      if (isa<PseudoProbeInst>(BI))
+        continue;
+
       BI->setDebugLoc(TheCallDL);
     }
 

llvm/test/Transforms/SampleProfile/pseudo-probe-no-debug-info.ll

@@ -0,0 +1,51 @@
+; RUN: opt < %s -passes='pseudo-probe,cgscc(inline)' -S | FileCheck %s
+
+
+; CHECK-LABEL: @caller(
+
+; This instruction did not have a !dbg metadata in the callee but get a !dbg after inlined.
+; CHECK: store i32 1, {{.*}}, !dbg ![[#]]
+
+; This pseudo probe came from callee without a !dbg metadata.
+; CHECK-NOT:  call void @llvm.pseudoprobe({{.*}}), !dbg ![[#]]
+; CHECK:  call void @llvm.pseudoprobe({{.*}})
+
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@a = common global i32 0, align 4
+@b = common global i32 0, align 4
+
+; Function Attrs: nounwind uwtable
+define void @callee() #0 {
+entry:
+  store i32 1, ptr @a, align 4
+  ret void
+}
+
+; Function Attrs: nounwind uwtable
+define void @caller() #0 !dbg !4 {
+entry:
+  tail call void @callee(), !dbg !12
+  ret void, !dbg !12
+}
+
+attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "frame-pointer"="none" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!8, !9}
+!llvm.ident = !{!10}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang version 3.5.0 (210174)", isOptimized: true, emissionKind: LineTablesOnly, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
+!1 = !DIFile(filename: "test.c", directory: "/code/llvm/build0")
+!2 = !{}
+!4 = distinct !DISubprogram(name: "caller", line: 4, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: true, unit: !0, scopeLine: 4, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!5 = !DIFile(filename: "test.c", directory: "/code/llvm/build0")
+!6 = !DISubroutineType(types: !2)
+!7 = distinct !DISubprogram(name: "callee2", line: 2, isLocal: true, isDefinition: true, virtualIndex: 6, isOptimized: true, unit: !0, scopeLine: 2, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!8 = !{i32 2, !"Dwarf Version", i32 4}
+!9 = !{i32 2, !"Debug Info Version", i32 3}
+!10 = !{!"clang version 3.5.0 (210174)"}
+!11 = !DILocation(line: 2, scope: !7)
+!12 = !DILocation(line: 4, scope: !4)