From 164ab9b4a416b23539cb4ca9e3baf48847222d5d Mon Sep 17 00:00:00 2001
From: Teresa Johnson <tejohnson@google.com>
Date: Sun, 19 Mar 2017 13:54:57 +0000
Subject: [PATCH] Enable stripping of multiple DILocation on !llvm.loop
 metadata

Summary:
I found that stripDebugInfo was still leaving significant amounts of
debug info due to !llvm.loop that contained DILocation after stripping.
The support for stripping debug info on !llvm.loop added in r293377 only
removes a single DILocation. Enhance that to remove all DILocation from
!llvm.loop.

Reviewers: hfinkel, aprantl, dsanders

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D31117

llvm-svn: 298213
---
 lib/IR/DebugInfo.cpp                  | 23 ++++++++------
 test/DebugInfo/strip-loop-metadata.ll | 44 +++++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 10 deletions(-)

diff --git a/lib/IR/DebugInfo.cpp b/lib/IR/DebugInfo.cpp
index 5e14723c3af..918fdc26068 100644
--- a/lib/IR/DebugInfo.cpp
+++ b/lib/IR/DebugInfo.cpp
@@ -241,26 +241,29 @@ bool DebugInfoFinder::addScope(DIScope *Scope) {
 
 static llvm::MDNode *stripDebugLocFromLoopID(llvm::MDNode *N) {
   assert(N->op_begin() != N->op_end() && "Missing self reference?");
-  auto DebugLocOp =
-      std::find_if(N->op_begin() + 1, N->op_end(), [](const MDOperand &Op) {
-        return isa<DILocation>(Op.get());
-      });
 
-  // No debug location, we do not have to rewrite this MDNode.
-  if (DebugLocOp == N->op_end())
+  // if there is no debug location, we do not have to rewrite this MDNode.
+  if (std::none_of(N->op_begin() + 1, N->op_end(), [](const MDOperand &Op) {
+        return isa<DILocation>(Op.get());
+      }))
     return N;
 
-  // There is only the debug location without any actual loop metadata, hence we
+  // If there is only the debug location without any actual loop metadata, we
   // can remove the metadata.
-  if (N->getNumOperands() == 2)
+  if (std::none_of(N->op_begin() + 1, N->op_end(), [](const MDOperand &Op) {
+        return !isa<DILocation>(Op.get());
+      }))
     return nullptr;
 
   SmallVector<Metadata *, 4> Args;
   // Reserve operand 0 for loop id self reference.
   auto TempNode = MDNode::getTemporary(N->getContext(), None);
   Args.push_back(TempNode.get());
-  Args.append(N->op_begin() + 1, DebugLocOp);
-  Args.append(DebugLocOp + 1, N->op_end());
+  // Add all non-debug location operands back.
+  for (auto Op = N->op_begin() + 1; Op != N->op_end(); Op++) {
+    if (!isa<DILocation>(*Op))
+      Args.push_back(*Op);
+  }
 
   // Set the first operand to itself.
   MDNode *LoopID = MDNode::get(N->getContext(), Args);
diff --git a/test/DebugInfo/strip-loop-metadata.ll b/test/DebugInfo/strip-loop-metadata.ll
index 1b1c9cac4e0..2d5addd9731 100644
--- a/test/DebugInfo/strip-loop-metadata.ll
+++ b/test/DebugInfo/strip-loop-metadata.ll
@@ -33,6 +33,34 @@ return:
   ret void, !dbg !21
 }
 
+; CHECK-LABEL: _Z5test3v
+; CHECK: br {{.*}} !llvm.loop [[LOOP2:![0-9]+]]
+define void @_Z5test3v() !dbg !22 {
+entry:
+  br label %while.body, !dbg !23
+
+while.body:
+  call void @_Z3barv(), !dbg !24
+  br label %while.body, !dbg !25, !llvm.loop !26
+
+return:
+  ret void, !dbg !28
+}
+
+; CHECK-LABEL: _Z5test4v
+; CHECK-NOT: br {{.*}} !llvm.loop
+define void @_Z5test4v() !dbg !30 {
+entry:
+  br label %while.body, !dbg !31
+
+while.body:
+  call void @_Z3barv(), !dbg !32
+  br label %while.body, !dbg !33, !llvm.loop !34
+
+return:
+  ret void, !dbg !36
+}
+
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!3, !4, !5}
 !llvm.ident = !{!6}
@@ -59,6 +87,21 @@ return:
 !19 = distinct !{!19, !16, !20}
 !20 = !{!"llvm.loop.unroll.enable"}
 !21 = !DILocation(line: 12, column: 1, scope: !15)
+!22 = distinct !DISubprogram(name: "test3", scope: !1, file: !1, line: 8, type: !8, isLocal: false, isDefinition: true, scopeLine: 8, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!23 = !DILocation(line: 8, column: 14, scope: !22)
+!24 = !DILocation(line: 11, column: 5, scope: !22)
+!25 = !DILocation(line: 10, column: 3, scope: !22)
+!26 = distinct !{!26, !23, !29, !27}
+!27 = !{!"llvm.loop.unroll.enable"}
+!28 = !DILocation(line: 12, column: 1, scope: !22)
+!29 = !DILocation(line: 12, column: 1, scope: !22)
+!30 = distinct !DISubprogram(name: "test4", scope: !1, file: !1, line: 8, type: !8, isLocal: false, isDefinition: true, scopeLine: 8, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!31 = !DILocation(line: 8, column: 14, scope: !30)
+!32 = !DILocation(line: 11, column: 5, scope: !30)
+!33 = !DILocation(line: 10, column: 3, scope: !30)
+!34 = distinct !{!34, !31, !35}
+!35 = !DILocation(line: 12, column: 1, scope: !30)
+!36 = !DILocation(line: 12, column: 1, scope: !30)
 
 ; CHECK-NOT: !DICompileUnit
 ; CHECK-NOT: !DIFile
@@ -68,4 +111,5 @@ return:
 ; CHECK-NOT: !DILexicalBlockFile
 ; CHECK: [[LOOP]] = distinct !{[[LOOP]], [[LOOP_UNROLL:![0-9]+]]}
 ; CHECK-NEXT: [[LOOP_UNROLL]] = !{!"llvm.loop.unroll.enable"}
+; CHECK: [[LOOP2]] = distinct !{[[LOOP2]], [[LOOP_UNROLL]]}
 ; CHECK-NOT: !DILocation