Allow norecurse attribute on functions that have debug infos.

[chrib]

Summary

debug intrinsics might be marked norecurse to enable the caller function to be norecurse and optimized if needed. This avoids code gen optimisation differences when -g is used, as in globalOpt.cpp:processInternalGlobal checks.

[aprantl]

Looks mostly good.

lib/Transforms/IPO/FunctionAttrs.cpp

1311

Is there something like on the function level?

http://www.llvm.org/doxygen/classllvm_1_1BasicBlock.html#a126c95a0ff18e58ac0c2c7439fb2dc6d

test/Transforms/InferFunctionAttrs/norecurse_debug.ll

54

Do you need the TBAA info for the testcase?

[chandlerc]

lib/Transforms/IPO/FunctionAttrs.cpp

1311

Yeah, I'd much prefer to iterate the filtered sequence here.

[chrib]

lib/Transforms/IPO/FunctionAttrs.cpp

1311

not at function level but yes I can iterate on the BBs something like:

for (auto &BB : *F) {
  for (auto &I : BB.instructionsWithoutDebug())

test/Transforms/InferFunctionAttrs/norecurse_debug.ll

54

indeed no, not related to this issue to the tbaa meta can be removed.

[chrib]

iterate with instructionsWithoutDebug
reduce testcase

lib/Transforms/IPO/FunctionAttrs.cpp

 #include "llvm/IR/InstrTypes.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/IR/Type.h"

   // If all of the calls in F are identifiable and are to norecurse functions, F
   // is norecurse. This check also detects self-recursion as F is not currently
   // marked norecurse, so any called from F to F will not be marked norecurse.
-  for (Instruction &I : instructions(*F))
-    if (auto CS = CallSite(&I)) {
-      Function *Callee = CS.getCalledFunction();
-      if (!Callee || Callee == F || !Callee->doesNotRecurse())
-        // Function calls a potentially recursive function.
-        return false;
-    }
+  for (auto &BB : *F)
+    for (auto &I : BB.instructionsWithoutDebug())
+      if (auto CS = CallSite(&I)) {
+        Function *Callee = CS.getCalledFunction();
+        if (!Callee || Callee == F || !Callee->doesNotRecurse())
+          // Function calls a potentially recursive function.
+          return false;
+      }
 
   // Every call was to a non-recursive function other than this function, and
   // we have no indirect recursion as the SCC size is one. This function cannot

test/Transforms/InferFunctionAttrs/norecurse_debug.ll

+; RUN: opt < %s -O2 -S | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv4t-none-unknown-eabi"
+
[e-mail]1 = internal unnamed_addr global i32* null, align 4, !dbg !0
+@iirLow1 = external dso_local local_unnamed_addr global i32*, align 4
+
+; Function Attrs: nounwind
+define dso_local void @foo(i32 %i2) local_unnamed_addr #0 !dbg !2 {
+entry:
+  call void @llvm.dbg.value(metadata i32 %i2, metadata !11, metadata !DIExpression()), !dbg !18
+  %0 = load i32*, i32** @iirLow1, align 4, !dbg !19
+  store i32 0, i32* %0, align 4, !dbg !24
+  %1 = ptrtoint i32* %0 to i32, !dbg !27
+  store i32 %1, i32* bitcast (i32** @foo.coefficient1 to i32*), align 4, !dbg !28
+  ret void, !dbg !29
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.value(metadata, metadata, metadata) #1
+
+attributes #0 = { nounwind }
+attributes #1 = { nounwind readnone speculatable }
+
+!llvm.dbg.cu = !{!7}
+!llvm.module.flags = !{!13, !14, !15, !16}
+!llvm.ident = !{!17}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "coefficient1", scope: !2, file: !3, line: 5, type: !12, isLocal: true, isDefinition: true)
+!2 = distinct !DISubprogram(name: "foo", scope: !3, file: !3, line: 3, type: !4, isLocal: false, isDefinition: true, scopeLine: 4, flags: DIFlagPrototyped, isOptimized: true, unit: !7, retainedNodes: !10)
+!3 = !DIFile(filename: "norecurse_debug.c", directory: "/")
+!4 = !DISubroutineType(types: !5)
+!5 = !{null, !6}
+!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!7 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !8, globals: !9, nameTableKind: None)
+!8 = !{}
+!9 = !{!0}
+!10 = !{!11}
+!11 = !DILocalVariable(name: "i2", arg: 1, scope: !2, file: !3, line: 3, type: !6)
+!12 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !6, size: 32)
+!13 = !{i32 2, !"Dwarf Version", i32 4}
+!14 = !{i32 2, !"Debug Info Version", i32 3}
+!15 = !{i32 1, !"wchar_size", i32 4}
+!16 = !{i32 1, !"min_enum_size", i32 4}
+!17 = !{!""}
+!18 = !DILocation(line: 3, column: 14, scope: !2)
+!19 = !DILocation(line: 7, column: 6, scope: !2)
+!24 = !DILocation(line: 7, column: 14, scope: !2)
+!27 = !DILocation(line: 9, column: 20, scope: !2)
+!28 = !DILocation(line: 9, column: 18, scope: !2)
+!29 = !DILocation(line: 10, column: 1, scope: !2)
+
+; CHECK: attributes #0 = { norecurse nounwind }
+; CHECK-NOT foo.coefficient1