Omit DW_TAG_subprograms for subprograms without inlined subroutines when producing...

To reduce the size of -gmlt data, skip the subprograms without any
inlined subroutines. Since we've now got the ability to make these
determinations in the backend (funnily enough - we added the flag so we
wouldn't produce ranges under -gmlt, but with this change we use the
flag, but go back to producing ranges under -gmlt).

Instead, just produce CU ranges to inform the consumer which parts of
the code are described by this CU's line table. Tools could inspect the
line table directly to compute the range, but the CU ranges only seem to
be about 0.5% of object/executable size, so I'm not too worried about
teaching llvm-symbolizer that trick just yet - it's certainly a possible
piece of future work.

Update an llvm-symbolizer test just to demonstrate that this schema is
acceptable there (if it wasn't, the compiler-rt tests would catch this,
but good to have an in-llvm-tree test for llvm-symbolizer's behavior
here)

Building the clang binary with -gmlt with this patch reduces the total
size of object files by 5.1% (5.56% without ranges) without compression
and the executable by 4.37% (4.75% without ranges).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218129 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 742646b0555e609759878f665903ffde143350fa..7cd0693124916653078e3594799d1d05a592cd61 100644 (file)
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -856,12 +856,14 @@ void DwarfDebug::finishSubprogramDefinitions() {
           // If this subprogram has an abstract definition, reference that
           SPCU->addDIEEntry(*D, dwarf::DW_AT_abstract_origin, *AbsSPDIE);
       } else {
-        if (!D)
+        if (!D && TheCU.getEmissionKind() != DIBuilder::LineTablesOnly)
           // Lazily construct the subprogram if we didn't see either concrete or
-          // inlined versions during codegen.
+          // inlined versions during codegen. (except in -gmlt ^ where we want
+          // to omit these entirely)
           D = SPCU->getOrCreateSubprogramDIE(SP);
-        // And attach the attributes
-        SPCU->applySubprogramAttributesToDefinition(SP, *D);
+        if (D)
+          // And attach the attributes
+          SPCU->applySubprogramAttributesToDefinition(SP, *D);
       }
     }
   }
@@ -1690,6 +1692,24 @@ void DwarfDebug::endFunction(const MachineFunction *MF) {
   LexicalScope *FnScope = LScopes.getCurrentFunctionScope();
   DwarfCompileUnit &TheCU = *SPMap.lookup(FnScope->getScopeNode());
 
+  // Add the range of this function to the list of ranges for the CU.
+  TheCU.addRange(RangeSpan(FunctionBeginSym, FunctionEndSym));
+
+  // Under -gmlt, skip building the subprogram if there are no inlined
+  // subroutines inside it.
+  if (TheCU.getCUNode().getEmissionKind() == DIBuilder::LineTablesOnly &&
+      LScopes.getAbstractScopesList().empty()) {
+    assert(ScopeVariables.empty());
+    assert(CurrentFnArguments.empty());
+    assert(DbgValues.empty());
+    assert(AbstractVariables.empty());
+    LabelsBeforeInsn.clear();
+    LabelsAfterInsn.clear();
+    PrevLabel = nullptr;
+    CurFn = nullptr;
+    return;
+  }
+
   // Construct abstract scopes.
   for (LexicalScope *AScope : LScopes.getAbstractScopesList()) {
     DISubprogram SP(AScope->getScopeNode());
@@ -1710,10 +1730,6 @@ void DwarfDebug::endFunction(const MachineFunction *MF) {
   if (!CurFn->getTarget().Options.DisableFramePointerElim(*CurFn))
     TheCU.addFlag(CurFnDIE, dwarf::DW_AT_APPLE_omit_frame_ptr);
 
-  // Add the range of this function to the list of ranges for the CU.
-  RangeSpan Span(FunctionBeginSym, FunctionEndSym);
-  TheCU.addRange(std::move(Span));
-
   // Clear debug info
   // Ownership of DbgVariables is a bit subtle - ScopeVariables owns all the
   // DbgVariables except those that are also in AbstractVariables (since they

diff --git a/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 4bf18db32ff5a0c5281c52df838d2e37dd5662a7..b6514e6b5d60e4bd0b77059a7e37dd6e0cb5ab94 100644 (file)
--- a/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -2049,23 +2049,20 @@ void DwarfUnit::emitHeader(const MCSymbol *ASectionSym) const {
 }
 
 void DwarfCompileUnit::addRange(RangeSpan Range) {
-  // Only add a range for this unit if we're emitting full debug.
-  if (getCUNode().getEmissionKind() == DIBuilder::FullDebug) {
-    bool SameAsPrevCU = this == DD->getPrevCU();
-    DD->setPrevCU(this);
-    // If we have no current ranges just add the range and return, otherwise,
-    // check the current section and CU against the previous section and CU we
-    // emitted into and the subprogram was contained within. If these are the
-    // same then extend our current range, otherwise add this as a new range.
-    if (CURanges.empty() || !SameAsPrevCU ||
-        (&CURanges.back().getEnd()->getSection() !=
-         &Range.getEnd()->getSection())) {
-      CURanges.push_back(Range);
-      return;
-    }
-
-    CURanges.back().setEnd(Range.getEnd());
+  bool SameAsPrevCU = this == DD->getPrevCU();
+  DD->setPrevCU(this);
+  // If we have no current ranges just add the range and return, otherwise,
+  // check the current section and CU against the previous section and CU we
+  // emitted into and the subprogram was contained within. If these are the
+  // same then extend our current range, otherwise add this as a new range.
+  if (CURanges.empty() || !SameAsPrevCU ||
+      (&CURanges.back().getEnd()->getSection() !=
+       &Range.getEnd()->getSection())) {
+    CURanges.push_back(Range);
+    return;
   }
+
+  CURanges.back().setEnd(Range.getEnd());
 }
 
 void DwarfCompileUnit::initStmtList(MCSymbol *DwarfLineSectionSym) {

diff --git a/test/DebugInfo/Inputs/dwarfdump-inl-test.elf-x86-64 b/test/DebugInfo/Inputs/dwarfdump-inl-test.elf-x86-64
index 6df03dad95a7823362d3e28f5a800b851e4db7c5..decc72b4ff22cb27155280462595fb87217d5f66 100755 (executable)
Binary files a/test/DebugInfo/Inputs/dwarfdump-inl-test.elf-x86-64 and b/test/DebugInfo/Inputs/dwarfdump-inl-test.elf-x86-64 differ

diff --git a/test/DebugInfo/gmlt.ll b/test/DebugInfo/gmlt.ll
index 9271b2ed9c9ccd7de402ec6d1c05c2d6442ba8c0..0c81c29ed7da9956f21b4723b1dd86546fb55ff5 100644 (file)
--- a/test/DebugInfo/gmlt.ll
+++ b/test/DebugInfo/gmlt.ll
@@ -1,33 +1,72 @@
 ; REQUIRES: object-emission
 ; RUN: %llc_dwarf -O0 -filetype=obj < %s | llvm-dwarfdump - | FileCheck %s
 
-; Generated from the following source compiled with clang -gmlt:
-; void f1(void) {}
-; void f2(void) __attribute__((section("__TEXT,__bar"))) {}
+; Generated from the following source compiled with clang++ -gmlt:
+; void f1() {}
+; void __attribute__((section("__TEXT,__bar"))) f2() {}
+; void __attribute__((always_inline)) f3() { f1(); }
+; void f4() { f3(); }
 
 ; Check that
-;  * -gmlt ('Emission Kind' of 'LineTablesOnly' in the CU debug info metadata)
-;    doesn't produce ranges.
-;  * if no ranges are produced, no debug_ranges list (not even an empty one) is
-;    emitted.
-
-; -gmlt means no DW_AT_ranges on the CU, even though there are parts of the CU
-; in different sections and this would normally necessitate a DW_AT_ranges
-; attribute on the CU.
+;  * -gmlt includes no DW_TAG_subprograms for subprograms without inlined
+;    subroutines.
+;  * yet still produces DW_AT_ranges and a range list in debug_ranges that
+;    describes those subprograms
+
 ; CHECK: DW_TAG_compile_unit
-; CHECK-NOT: DW_AT_ranges
+; CHECK:   DW_AT_ranges [DW_FORM_sec_offset] (0x00000000)
 ; CHECK-NOT: {{DW_TAG|NULL}}
+
+
+; FIXME: Emitting separate abstract definitions is inefficient when we could
+; just attach the DW_AT_name to the inlined_subroutine directly. Except that
+; would produce many string relocations. Implement string indexing in the
+; skeleton CU to address the relocation problem, then remove abstract
+; definitions from -gmlt here.
+
+; CHECK: [[F3_ABS_DEF:.*]]:  DW_TAG_subprogram
+; CHECK-NEXT:     DW_AT_name {{.*}} "f3"
+
+; FIXME: We don't really need DW_AT_inline, consumers can ignore this due to
+; the absence of high_pc/low_pc/ranges and know that they just need it for
+; retrieving the name of a concrete inlined instance
+
+; CHECK-NEXT:     DW_AT_inline
+; CHECK-NOT: {{DW_TAG|DW_AT|NULL}}
+
 ; Check that we only provide the minimal attributes on a subprogram to save space.
 ; CHECK:   DW_TAG_subprogram
 ; CHECK-NEXT:     DW_AT_low_pc
 ; CHECK-NEXT:     DW_AT_high_pc
 ; CHECK-NEXT:     DW_AT_name
-; CHECK-NOT: DW_AT
-; CHECK: {{DW_TAG|NULL}}
+; CHECK-NOT: {{DW_TAG|DW_AT}}
+; CHECK:     DW_TAG_inlined_subroutine
+
+; As mentioned above - replace DW_AT_abstract_origin with DW_AT_name to save
+; space once we have support for string indexing in non-dwo sections
+
+; CHECK-NEXT:       DW_AT_abstract_origin {{.*}} {[[F3_ABS_DEF]]}
+; CHECK-NEXT:       DW_AT_low_pc
+; CHECK-NEXT:       DW_AT_high_pc
+; CHECK-NEXT:       DW_AT_call_file
+; CHECK-NEXT:       DW_AT_call_line
+
+; Make sure we don't have any other subprograms here (subprograms with no
+; inlined subroutines are omitted by design to save space)
 
-; FIXME: We probably want to avoid printing out anything if the section isn't there.
+; CHECK-NOT: {{DW_TAG|DW_AT}}
+; CHECK: NULL
+; CHECK-NOT: {{DW_TAG|DW_AT}}
+; CHECK: NULL
+
+
+; FIXME: llvm-dwarfdump should detect the relocations here and realize that the
+; first two "end of list" are really just unrelocated values describing the two
+; functions in the CU.
 ; CHECK: .debug_ranges contents:
-; CHECK-NOT: 00000000 <End of list>
+; CHECK: 00000000 <End of list>
+; CHECK: 00000010 <End of list>
+; CHECK: 00000020 <End of list>
 
 ; Check that we don't emit any pubnames or pubtypes under -gmlt
 ; CHECK: .debug_pubnames contents:
@@ -37,33 +76,56 @@
 ; CHECK-NOT: Offset
 
 ; Function Attrs: nounwind uwtable
-define void @f1() #0 {
+define void @_Z2f1v() #0 {
+entry:
+  ret void, !dbg !13
+}
+
+; Function Attrs: nounwind uwtable
+define void @_Z2f2v() #0 section "__TEXT,__bar" {
+entry:
+  ret void, !dbg !14
+}
+
+; Function Attrs: alwaysinline nounwind uwtable
+define void @_Z2f3v() #1 {
 entry:
-  ret void, !dbg !11
+  call void @_Z2f1v(), !dbg !15
+  ret void, !dbg !16
 }
 
 ; Function Attrs: nounwind uwtable
-define void @f2() #0 section "__TEXT,__bar" {
+define void @_Z2f4v() #0 {
 entry:
-  ret void, !dbg !12
+  call void @_Z2f1v() #2, !dbg !17
+  ret void, !dbg !19
 }
 
 attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { alwaysinline nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #2 = { nounwind }
 
 !llvm.dbg.cu = !{!0}
-!llvm.module.flags = !{!8, !9}
-!llvm.ident = !{!10}
+!llvm.module.flags = !{!10, !11}
+!llvm.ident = !{!12}
 
-!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.6.0 ", i1 false, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !"", i32 2} ; [ DW_TAG_compile_unit ] [/tmp/dbginfo/cu-line-tables.c] [DW_LANG_C99]
-!1 = metadata !{metadata !"cu-line-tables.c", metadata !"/tmp/dbginfo"}
+!0 = metadata !{i32 786449, metadata !1, i32 4, metadata !"clang version 3.6.0 ", i1 false, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !"", i32 2} ; [ DW_TAG_compile_unit ] [/tmp/dbginfo/gmlt.cpp] [DW_LANG_C_plus_plus]
+!1 = metadata !{metadata !"gmlt.cpp", metadata !"/tmp/dbginfo"}
 !2 = metadata !{}
-!3 = metadata !{metadata !4, metadata !7}
-!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f1", metadata !"f1", metadata !"", i32 1, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, void ()* @f1, null, null, metadata !2, i32 1} ; [ DW_TAG_subprogram ] [line 1] [def] [f1]
-!5 = metadata !{i32 786473, metadata !1}          ; [ DW_TAG_file_type ] [/tmp/dbginfo/cu-line-tables.c]
+!3 = metadata !{metadata !4, metadata !7, metadata !8, metadata !9}
+!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f1", metadata !"f1", metadata !"", i32 1, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, void ()* @_Z2f1v, null, null, metadata !2, i32 1} ; [ DW_TAG_subprogram ] [line 1] [def] [f1]
+!5 = metadata !{i32 786473, metadata !1}          ; [ DW_TAG_file_type ] [/tmp/dbginfo/gmlt.cpp]
 !6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !2, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
-!7 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f2", metadata !"f2", metadata !"", i32 2, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, void ()* @f2, null, null, metadata !2, i32 2} ; [ DW_TAG_subprogram ] [line 2] [def] [f2]
-!8 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
-!9 = metadata !{i32 2, metadata !"Debug Info Version", i32 1}
-!10 = metadata !{metadata !"clang version 3.6.0 "}
-!11 = metadata !{i32 1, i32 16, metadata !4, null}
-!12 = metadata !{i32 2, i32 48, metadata !7, null}
+!7 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f2", metadata !"f2", metadata !"", i32 2, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, void ()* @_Z2f2v, null, null, metadata !2, i32 2} ; [ DW_TAG_subprogram ] [line 2] [def] [f2]
+!8 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f3", metadata !"f3", metadata !"", i32 3, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, void ()* @_Z2f3v, null, null, metadata !2, i32 3} ; [ DW_TAG_subprogram ] [line 3] [def] [f3]
+!9 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f4", metadata !"f4", metadata !"", i32 4, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, void ()* @_Z2f4v, null, null, metadata !2, i32 4} ; [ DW_TAG_subprogram ] [line 4] [def] [f4]
+!10 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
+!11 = metadata !{i32 2, metadata !"Debug Info Version", i32 1}
+!12 = metadata !{metadata !"clang version 3.6.0 "}
+!13 = metadata !{i32 1, i32 12, metadata !4, null}
+!14 = metadata !{i32 2, i32 53, metadata !7, null}
+!15 = metadata !{i32 3, i32 44, metadata !8, null}
+!16 = metadata !{i32 3, i32 50, metadata !8, null}
+!17 = metadata !{i32 3, i32 44, metadata !8, metadata !18}
+!18 = metadata !{i32 4, i32 13, metadata !9, null}
+!19 = metadata !{i32 4, i32 19, metadata !9, null}

diff --git a/test/DebugInfo/llvm-symbolizer.test b/test/DebugInfo/llvm-symbolizer.test
index fdd64d69f5b300306573eb6e4fe5f7f75fb5e8b9..40a051e327ac7a2a09f3f5d9ae38a3e14c49cf3d 100644 (file)
--- a/test/DebugInfo/llvm-symbolizer.test
+++ b/test/DebugInfo/llvm-symbolizer.test
@@ -6,9 +6,9 @@ RUN: echo "%p/Inputs/dwarfdump-test.elf-x86-64 0x400586" >> %t.input
 RUN: echo "%p/Inputs/dwarfdump-test2.elf-x86-64 0x4004e8" >> %t.input
 RUN: echo "%p/Inputs/dwarfdump-test2.elf-x86-64 0x4004f4" >> %t.input
 RUN: echo "%p/Inputs/dwarfdump-test4.elf-x86-64 0x62c" >> %t.input
-RUN: echo "%p/Inputs/dwarfdump-inl-test.elf-x86-64 0x710" >> %t.input
-RUN: echo "%p/Inputs/dwarfdump-inl-test.elf-x86-64 0x7d1" >> %t.input
-RUN: echo "%p/Inputs/dwarfdump-inl-test.elf-x86-64 0x785" >> %t.input
+RUN: echo "%p/Inputs/dwarfdump-inl-test.elf-x86-64 0x8dc" >> %t.input
+RUN: echo "%p/Inputs/dwarfdump-inl-test.elf-x86-64 0xa05" >> %t.input
+RUN: echo "%p/Inputs/dwarfdump-inl-test.elf-x86-64 0x987" >> %t.input
 RUN: echo "%p/Inputs/dwarfdump-inl-test.high_pc.elf-x86-64 0x568" >> %t.input
 RUN: echo "\"%p/Inputs/dwarfdump-test3.elf-x86-64 space\" 0x640" >> %t.input
 RUN: echo "\"%p/Inputs/dwarfdump-test3.elf-x86-64 space\" 0x633" >> %t.input