From fce148c5686f4c3944bcecb141ebf5eb9102ea22 Mon Sep 17 00:00:00 2001
From: Dmitry Mikulin <dmitry.mikulin@sony.com>
Date: Tue, 16 May 2017 20:08:49 +0000
Subject: [PATCH] In debug builds non-trivial amount of time is spent in
 InstCombine processing @llvm.dbg.* calls in visitCallInst(). They can be
 safely ignored.

llvm-svn: 303202
---
 .../InstCombine/InstructionCombining.cpp           |  5 ++-
 llvm/test/Transforms/InstCombine/debuginfo-skip.ll | 43 ++++++++++++++++++++++
 2 files changed, 47 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/Transforms/InstCombine/debuginfo-skip.ll

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 65b1148..3dd3c29 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3053,7 +3053,10 @@ static bool AddReachableCodeToWorklist(BasicBlock *BB, const DataLayout &DL,
         }
       }
 
-      InstrsForInstCombineWorklist.push_back(Inst);
+      // Skip processing debug intrinsics in InstCombine. Processing these call instructions
+      // consumes non-trivial amount of time and provides no value for the optimization.
+      if (!isa<DbgInfoIntrinsic>(Inst))
+        InstrsForInstCombineWorklist.push_back(Inst);
     }
 
     // Recursively visit successors.  If this is a branch or switch on a
diff --git a/llvm/test/Transforms/InstCombine/debuginfo-skip.ll b/llvm/test/Transforms/InstCombine/debuginfo-skip.ll
new file mode 100644
index 0000000..d591100
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/debuginfo-skip.ll
@@ -0,0 +1,43 @@
+; RUN: opt < %s -instcombine -debug -S -o %t 2>&1 | FileCheck %s
+; RUN: cat %t | FileCheck %s --check-prefix=CHECK-IR
+
+; Debug output from InstCombine should not have any @llvm.dbg.* instructions visited
+; CHECK-NOT: call void @llvm.dbg.
+
+; The resulting IR should still have them
+; CHECK-IR: call void @llvm.dbg.
+
+define i32 @foo(i32 %j) #0 !dbg !7 {
+entry:
+  %j.addr = alloca i32, align 4
+  store i32 %j, i32* %j.addr, align 4
+  call void @llvm.dbg.declare(metadata i32* %j.addr, metadata !11, metadata !12), !dbg !13
+  call void @llvm.dbg.value(metadata i32 10, i64 0, metadata !16, metadata !12), !dbg !15
+  %0 = load i32, i32* %j.addr, align 4, !dbg !14
+  ret i32 %0, !dbg !15
+}
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang 5.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "a.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"PIC Level", i32 2}
+!6 = !{!"clang version 5.0.0 (trunk 302918) (llvm/trunk 302925)"}
+!7 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 2, type: !8, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10, !10}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !DILocalVariable(name: "j", arg: 1, scope: !7, file: !1, line: 2, type: !10)
+!12 = !DIExpression()
+!13 = !DILocation(line: 2, column: 13, scope: !7)
+!14 = !DILocation(line: 5, column: 10, scope: !7)
+!15 = !DILocation(line: 5, column: 3, scope: !7)
+!16 = !DILocalVariable(name: "h", scope: !7, file: !1, line: 4, type: !10)
-- 
2.7.4