Add new debug kind LocTrackingOnly.

Summary:
This new debug emission kind supports emitting line location
information in all instructions, but stops code generation
from emitting debug info to the final output.

This mode is useful when the backend wants to track source
locations during code generation, but it does not want to
produce debug info. This is currently used by optimization
remarks (-pass-remarks, -pass-remarks-missed and
-pass-remarks-analysis).

To prevent debug info emission, DIBuilder never inserts the
annotation 'llvm.dbg.cu' when LocTrackingOnly is enabled.

Reviewers: echristo, dblaikie

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D4234

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211609 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/IR/DIBuilder.h b/include/llvm/IR/DIBuilder.h
index 8b05bbb4fdb7ed2778d0cfa2f5768a31969c26d0..267350409604c9ee304eb5d58e1f4509f2b83bee 100644 (file)
--- a/include/llvm/IR/DIBuilder.h
+++ b/include/llvm/IR/DIBuilder.h
@@ -108,12 +108,23 @@ namespace llvm {
     ///                 Objective-C.
     /// @param SplitName The name of the file that we'll split debug info out
     ///                  into.
+    /// @param Kind     The kind of debug information to generate.
+    /// @param EmitDebugInfo   A boolean flag which indicates whether debug
+    ///                        information should be written to the final
+    ///                        output or not. When this is false, debug
+    ///                        information annotations will be present in
+    ///                        the IL but they are not written to the final
+    ///                        assembly or object file. This supports tracking
+    ///                        source location information in the back end
+    ///                        without actually changing the output (e.g.,
+    ///                        when using optimization remarks).
     DICompileUnit createCompileUnit(unsigned Lang, StringRef File,
                                     StringRef Dir, StringRef Producer,
                                     bool isOptimized, StringRef Flags,
                                     unsigned RV,
                                     StringRef SplitName = StringRef(),
-                                    DebugEmissionKind Kind = FullDebug);
+                                    DebugEmissionKind Kind = FullDebug,
+                                    bool EmitDebugInfo = true);
 
     /// createFile - Create a file descriptor to hold debugging information
     /// for a file.

diff --git a/lib/IR/DIBuilder.cpp b/lib/IR/DIBuilder.cpp
index 92edacc04a77440842a37c7d0618ba17b3b3b5dd..11350401c7bf2ee4412cd9807658f08400b6f6e5 100644 (file)
--- a/lib/IR/DIBuilder.cpp
+++ b/lib/IR/DIBuilder.cpp
@@ -102,7 +102,8 @@ DICompileUnit DIBuilder::createCompileUnit(unsigned Lang, StringRef Filename,
                                            StringRef Producer, bool isOptimized,
                                            StringRef Flags, unsigned RunTimeVer,
                                            StringRef SplitName,
-                                           DebugEmissionKind Kind) {
+                                           DebugEmissionKind Kind,
+                                           bool EmitDebugInfo) {
 
   assert(((Lang <= dwarf::DW_LANG_OCaml && Lang >= dwarf::DW_LANG_C89) ||
           (Lang <= dwarf::DW_LANG_hi_user && Lang >= dwarf::DW_LANG_lo_user)) &&
@@ -140,8 +141,14 @@ DICompileUnit DIBuilder::createCompileUnit(unsigned Lang, StringRef Filename,
   MDNode *CUNode = MDNode::get(VMContext, Elts);
 
   // Create a named metadata so that it is easier to find cu in a module.
-  NamedMDNode *NMD = M.getOrInsertNamedMetadata("llvm.dbg.cu");
-  NMD->addOperand(CUNode);
+  // Note that we only generate this when the caller wants to actually
+  // emit debug information. When we are only interested in tracking
+  // source line locations throughout the backend, we prevent codegen from
+  // emitting debug info in the final output by not generating llvm.dbg.cu.
+  if (EmitDebugInfo) {
+    NamedMDNode *NMD = M.getOrInsertNamedMetadata("llvm.dbg.cu");
+    NMD->addOperand(CUNode);
+  }
 
   return DICompileUnit(CUNode);
 }

diff --git a/test/Transforms/LoopVectorize/X86/vectorization-remarks.ll b/test/Transforms/LoopVectorize/X86/vectorization-remarks.ll
index 685d034f219acdf933d6a8fafef8fc4323e2a97f..f1641762fdc00d13c1cc5151bf82bd924815501b 100644 (file)
--- a/test/Transforms/LoopVectorize/X86/vectorization-remarks.ll
+++ b/test/Transforms/LoopVectorize/X86/vectorization-remarks.ll
@@ -1,6 +1,13 @@
 ; RUN: opt < %s -loop-vectorize -mtriple=x86_64-unknown-linux -S -pass-remarks='loop-vectorize' 2>&1 | FileCheck -check-prefix=VECTORIZED %s
 ; RUN: opt < %s -loop-vectorize -force-vector-width=1 -force-vector-unroll=4 -mtriple=x86_64-unknown-linux -S -pass-remarks='.*vectorize.*' 2>&1 | FileCheck -check-prefix=UNROLLED %s
 
+; This code has all the !dbg annotations needed to track source line information,
+; but is missing the llvm.dbg.cu annotation. This prevents code generation from
+; emitting debug info in the final output.
+; RUN: llc -mtriple x86_64-pc-linux-gnu %s -o - | FileCheck -check-prefix=DEBUG-OUTPUT %s
+; DEBUG-OUTPUT-NOT: .loc
+; DEBUG-OUTPUT-NOT: {{.*}}.debug_info
+
 ; VECTORIZED: remark: {{.*}}.c:17:8: vectorized loop (vectorization factor: 4, unrolling interleave factor: 1)
 ; UNROLLED: remark: {{.*}}.c:17:8: unrolled with interleaving factor 4 (vectorization not beneficial)
 
@@ -37,11 +44,9 @@ for.end:                                          ; preds = %for.body
 
 declare void @ibar(i32*) #1
 
-!llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!7, !8}
 !llvm.ident = !{!9}
 
-!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.5.0 ", i1 true, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !"", i32 2} ; [ DW_TAG_compile_unit ] [./vectorization-remarks.c] [DW_LANG_C99]
 !1 = metadata !{metadata !"vectorization-remarks.c", metadata !"."}
 !2 = metadata !{}
 !3 = metadata !{metadata !4}