[DwarfDebug] Improve multi-BB single location detection in validThroughout (3/4)

With the changes introduced in D86151 we can now check for single locations
which span multiple blocks for inlined scopes and blocks.

D86151 introduced the InstructionOrdering parameter, replacing a scan through
MBB instructions. The functionality to compare instruction positions across
blocks was add there, and this patch just removes the exit checks that were
previously (but no longer) required.

CTMark shows a geomean binary size reduction of 2.2% for RelWithDebInfo builds.
llvm-locstats (using D85636) shows a very small variable location coverage
change in 5 of 10 binaries, but just like in D86151 it is only in the order of
10s of bytes.

Reviewed By: djtodoro

Differential Revision: https://reviews.llvm.org/D86152

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 404fb2f..72065a1 100644 (file)
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1538,13 +1538,6 @@ static bool validThroughout(LexicalScopes &LScopes,
   if (LScopeBegin->getParent() != MBB)
     return false;
 
-  // If there are instructions belonging to our scope in another block, and
-  // we're not a constant (see DWARF2 comment below), then we can't be
-  // validThroughout.
-  const MachineInstr *LScopeEnd = LSRange.back().second;
-  if (RangeEnd && LScopeEnd->getParent() != MBB)
-    return false;
-
   MachineBasicBlock::const_reverse_iterator Pred(DbgValue);
   for (++Pred; Pred != MBB->rend(); ++Pred) {
     if (Pred->getFlag(MachineInstr::FrameSetup))
@@ -1572,21 +1565,8 @@ static bool validThroughout(LexicalScopes &LScopes,
   if (DbgValue->getDebugOperand(0).isImm() && MBB->pred_empty())
     return true;
 
-  // Now check for situations where an "open-ended" DBG_VALUE isn't enough to
-  // determine eligibility for a single location, e.g. nested scopes, inlined
-  // functions.
-  // FIXME: For now we just handle a simple (but common) case where the scope
-  // is contained in MBB. We could be smarter here.
-  //
-  // At this point we know that our scope ends in MBB. So, if RangeEnd exists
-  // outside of the block we can ignore it; the location is just leaking outside
-  // its scope.
-  assert(LScopeEnd->getParent() == MBB && "Scope ends outside MBB");
-  if (RangeEnd->getParent() != DbgValue->getParent())
-    return true;
-
-  // The location range and variable's enclosing scope are both contained within
-  // MBB, test if location terminates before end of scope.
+  // Test if the location terminates before the end of the scope.
+  const MachineInstr *LScopeEnd = LSRange.back().second;
   if (Ordering.isBefore(RangeEnd, LScopeEnd))
     return false;
 

diff --git a/llvm/test/DebugInfo/AArch64/inlined-argument.ll b/llvm/test/DebugInfo/AArch64/inlined-argument.ll
index 747d6d7..4fb7663 100644 (file)
--- a/llvm/test/DebugInfo/AArch64/inlined-argument.ll
+++ b/llvm/test/DebugInfo/AArch64/inlined-argument.ll
@@ -4,14 +4,8 @@
 ; CHECK-NEXT:  DW_AT_location  (DW_OP_reg1 W1)
 ; CHECK-NEXT:  DW_AT_abstract_origin {{.*}}"resource"
 ;
-; XFAIL: *
-; This test now fails as it requires the single-location variable recognizer
-; to spot that the inlined function goes out of scope before the 'find.exit'
-; exit block. Previously, unchanging variable locations could be extended to
-; the end of the function, often erronously, and that's why this test used to
-; pass.
-; A future algorithm _should_ be able to recognize that "resource"/!37 covers
-; all blocks in its lexical scope.
+; Inlined variable "resource"/!37 covers all blocks in its lexical scope. Check
+; that it is given a single location.
 ;
 ; Generated from:
 ; typedef struct t *t_t;

diff --git a/llvm/test/DebugInfo/X86/location-range-inlined-xblock.mir b/llvm/test/DebugInfo/X86/location-range-inlined-xblock.mir
new file mode 100644 (file)
index 0000000..1a39006
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/location-range-inlined-xblock.mir
@@ -0,0 +1,172 @@
+# RUN: llc -start-after=livedebugvalues --filetype=obj %s -o - \
+# RUN:   | llvm-dwarfdump -v --name local - \
+# RUN:   | FileCheck %s
+#
+## Generated with opt -inline -mem2reg, llc -stop-after=livedebugvalues from:
+## int glob;
+## int ext1(int);
+## int ext2(int);
+##
+## __attribute__((always_inline))
+## static int inline_me() {
+##   int local = glob;
+##   int r = 0;
+##   if (local)
+##     r = ext1(local);
+##   else
+##     r = ext2(local);
+##   return r * local;
+## }
+##
+## int fun(int p) {
+##   glob = p;
+##   glob = inline_me();
+##   return 0;
+## }
+##
+## Check that the location for inlined variable 'local' (RBX), which spans
+## multiple basic blocks, is given a single location.
+#
+# CHECK:      DW_AT_location [DW_FORM_exprloc] (DW_OP_reg3 RBX)
+# CHECK-NEXT: DW_AT_abstract_origin [DW_FORM_ref4] ({{.*}}"local")
+
+--- |
+  target triple = "x86_64-unknown-linux-gnu"
+
+  @glob = dso_local global i32 0, align 4, !dbg !0
+
+  define dso_local i32 @_Z3funi(i32 %p) !dbg !11 {
+  entry:
+    call void @llvm.dbg.value(metadata i32 %p, metadata !15, metadata !DIExpression()), !dbg !16
+    store i32 %p, i32* @glob, align 4, !dbg !17
+    %0 = load i32, i32* @glob, align 4, !dbg !22
+    call void @llvm.dbg.value(metadata i32 %0, metadata !27, metadata !DIExpression()), !dbg !30
+    call void @llvm.dbg.value(metadata i32 0, metadata !28, metadata !DIExpression()), !dbg !30
+    %tobool.i = icmp ne i32 %0, 0, !dbg !31
+    br i1 %tobool.i, label %if.then.i, label %if.else.i, !dbg !33
+
+  if.then.i:                                        ; preds = %entry
+    %call.i = call i32 @_Z4ext1i(i32 %0), !dbg !34
+    call void @llvm.dbg.value(metadata i32 %call.i, metadata !28, metadata !DIExpression()), !dbg !30
+    br label %_ZL9inline_mev.exit, !dbg !35
+
+  if.else.i:                                        ; preds = %entry
+    %call1.i = call i32 @_Z4ext2i(i32 %0), !dbg !36
+    call void @llvm.dbg.value(metadata i32 %call1.i, metadata !28, metadata !DIExpression()), !dbg !30
+    br label %_ZL9inline_mev.exit
+
+  _ZL9inline_mev.exit:                              ; preds = %if.else.i, %if.then.i
+    %r.0.i = phi i32 [ %call.i, %if.then.i ], [ %call1.i, %if.else.i ], !dbg !37
+    call void @llvm.dbg.value(metadata i32 %r.0.i, metadata !28, metadata !DIExpression()), !dbg !30
+    %mul.i = mul nsw i32 %r.0.i, %0, !dbg !38
+    store i32 %mul.i, i32* @glob, align 4, !dbg !39
+    ret i32 0, !dbg !40
+  }
+
+  declare !dbg !41 dso_local i32 @_Z4ext1i(i32)
+  declare !dbg !42 dso_local i32 @_Z4ext2i(i32)
+  declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+  !llvm.dbg.cu = !{!2}
+  !llvm.module.flags = !{!7, !8, !9}
+  !llvm.ident = !{!10}
+
+  !0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+  !1 = distinct !DIGlobalVariable(name: "glob", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
+  !2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !3, producer: "clang version 12.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, splitDebugInlining: false, nameTableKind: None)
+  !3 = !DIFile(filename: "test.cpp", directory: "/")
+  !4 = !{}
+  !5 = !{!0}
+  !6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+  !7 = !{i32 7, !"Dwarf Version", i32 4}
+  !8 = !{i32 2, !"Debug Info Version", i32 3}
+  !9 = !{i32 1, !"wchar_size", i32 4}
+  !10 = !{!"clang version 12.0.0"}
+  !11 = distinct !DISubprogram(name: "fun", linkageName: "_Z3funi", scope: !3, file: !3, line: 16, type: !12, scopeLine: 16, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !14)
+  !12 = !DISubroutineType(types: !13)
+  !13 = !{!6, !6}
+  !14 = !{!15}
+  !15 = !DILocalVariable(name: "p", arg: 1, scope: !11, file: !3, line: 16, type: !6)
+  !16 = !DILocation(line: 0, scope: !11)
+  !17 = !DILocation(line: 17, column: 8, scope: !11)
+  !22 = !DILocation(line: 7, column: 15, scope: !23, inlinedAt: !29)
+  !23 = distinct !DISubprogram(name: "inline_me", linkageName: "_ZL9inline_mev", scope: !3, file: !3, line: 6, type: !24, scopeLine: 6, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !26)
+  !24 = !DISubroutineType(types: !25)
+  !25 = !{!6}
+  !26 = !{!27, !28}
+  !27 = !DILocalVariable(name: "local", scope: !23, file: !3, line: 7, type: !6)
+  !28 = !DILocalVariable(name: "r", scope: !23, file: !3, line: 8, type: !6)
+  !29 = distinct !DILocation(line: 18, column: 10, scope: !11)
+  !30 = !DILocation(line: 0, scope: !23, inlinedAt: !29)
+  !31 = !DILocation(line: 9, column: 7, scope: !32, inlinedAt: !29)
+  !32 = distinct !DILexicalBlock(scope: !23, file: !3, line: 9, column: 7)
+  !33 = !DILocation(line: 9, column: 7, scope: !23, inlinedAt: !29)
+  !34 = !DILocation(line: 10, column: 9, scope: !32, inlinedAt: !29)
+  !35 = !DILocation(line: 10, column: 5, scope: !32, inlinedAt: !29)
+  !36 = !DILocation(line: 12, column: 9, scope: !32, inlinedAt: !29)
+  !37 = !DILocation(line: 0, scope: !32, inlinedAt: !29)
+  !38 = !DILocation(line: 13, column: 12, scope: !23, inlinedAt: !29)
+  !39 = !DILocation(line: 18, column: 8, scope: !11)
+  !40 = !DILocation(line: 19, column: 3, scope: !11)
+  !41 = !DISubprogram(name: "ext1", linkageName: "_Z4ext1i", scope: !3, file: !3, line: 2, type: !12, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !4)
+  !42 = !DISubprogram(name: "ext2", linkageName: "_Z4ext2i", scope: !3, file: !3, line: 3, type: !12, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !4)
+
+...
+---
+name:            _Z3funi
+body:             |
+  bb.0.entry:
+    successors: %bb.1(0x50000000), %bb.2(0x30000000)
+    liveins: $edi, $rbx
+
+    DBG_VALUE $edi, $noreg, !15, !DIExpression(), debug-location !16
+    frame-setup PUSH64r killed $rbx, implicit-def $rsp, implicit $rsp
+    CFI_INSTRUCTION def_cfa_offset 16
+    CFI_INSTRUCTION offset $rbx, -16
+    $ebx = MOV32rr $edi
+    DBG_VALUE $ebx, $noreg, !15, !DIExpression(), debug-location !16
+    MOV32mr $rip, 1, $noreg, @glob, $noreg, $edi, debug-location !17 :: (store 4 into @glob)
+    DBG_VALUE $ebx, $noreg, !27, !DIExpression(), debug-location !30
+    DBG_VALUE 0, $noreg, !28, !DIExpression(), debug-location !30
+    TEST32rr $edi, $edi, implicit-def $eflags, debug-location !31
+    JCC_1 %bb.2, 4, implicit killed $eflags, debug-location !33
+
+  bb.1.if.then.i:
+    successors: %bb.3(0x80000000)
+    liveins: $ebx
+
+    DBG_VALUE $ebx, $noreg, !27, !DIExpression(), debug-location !30
+    DBG_VALUE $ebx, $noreg, !15, !DIExpression(), debug-location !16
+    DBG_VALUE 0, $noreg, !28, !DIExpression(), debug-location !30
+    $edi = MOV32rr $ebx, debug-location !34
+    CALL64pcrel32 @_Z4ext1i, csr_64, implicit $rsp, implicit $ssp, implicit $edi, implicit-def $rsp, implicit-def $ssp, implicit-def $eax, debug-location !34
+    DBG_VALUE $eax, $noreg, !28, !DIExpression(), debug-location !30
+    JMP_1 %bb.3
+
+  bb.2.if.else.i:
+    successors: %bb.3(0x80000000)
+    liveins: $ebx
+
+    DBG_VALUE $ebx, $noreg, !27, !DIExpression(), debug-location !30
+    DBG_VALUE $ebx, $noreg, !15, !DIExpression(), debug-location !16
+    DBG_VALUE 0, $noreg, !28, !DIExpression(), debug-location !30
+    $edi = MOV32rr $ebx, debug-location !36
+    CALL64pcrel32 @_Z4ext2i, csr_64, implicit $rsp, implicit $ssp, implicit $edi, implicit-def $rsp, implicit-def $ssp, implicit-def $eax, debug-location !36
+    DBG_VALUE $eax, $noreg, !28, !DIExpression(), debug-location !30
+
+  bb.3._ZL9inline_mev.exit:
+    liveins: $eax, $ebx
+
+    DBG_VALUE $ebx, $noreg, !27, !DIExpression(), debug-location !30
+    DBG_VALUE $ebx, $noreg, !15, !DIExpression(), debug-location !16
+    DBG_VALUE $eax, $noreg, !28, !DIExpression(), debug-location !30
+    DBG_VALUE $eax, $noreg, !28, !DIExpression(), debug-location !30
+    renamable $eax = nsw IMUL32rr killed renamable $eax, killed renamable $ebx, implicit-def dead $eflags, debug-location !38
+    MOV32mr $rip, 1, $noreg, @glob, $noreg, killed renamable $eax, debug-location !39 :: (store 4 into @glob)
+    $eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, debug-location !40
+    $rbx = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !40
+    DBG_VALUE $edi, $noreg, !15, !DIExpression(DW_OP_LLVM_entry_value, 1), debug-location !16
+    CFI_INSTRUCTION def_cfa_offset 8, debug-location !40
+    RETQ $eax, debug-location !40
+
+...