[DebugInfo] More strict debug range for stack variables

Variable's stack location can stretch longer than it should. If a
variable is placed at the stack in a some nested basic block its range
can be calculated to be up to the next occurrence of the variable's
DBG_VALUE, or up to the end of the function, thus covering a basic
blocks that should not be included in the variable’s location range.
This happens because the DbgEntityHistoryCalculator ends register
locations at the end of a basic block only if the variable’s location
register has been changed throughout the function, which is not the
case for the register used to reference stack objects.

This patch also tries to produce a single value location if the location
list builder managed to merge all the locations into one.

Reviewers: aprantl, dstenb, jmorse

Reviewed By: aprantl, dstenb, jmorse

Subscribers: djtodoro, ivanbaev, asowda

Tags: #debug-info

Differential Revision: https://reviews.llvm.org/D61600

llvm-svn: 362923

2 files changed, 185 insertions, 1 deletions

diff --git a/llvm/test/DebugInfo/MIR/X86/dbg-stack-value-range.mir b/llvm/test/DebugInfo/MIR/X86/dbg-stack-value-range.mir
new file mode 100644
index 00000000000..3863f43b374
--- /dev/null
+++ b/llvm/test/DebugInfo/MIR/X86/dbg-stack-value-range.mir
@@ -0,0 +1,184 @@
+# RUN: llc -start-before=livedebugvalues %s -filetype=asm -o -| FileCheck %s
+#
+# DbgEntityHistoryCalculator should close variable's range at the end of
+# the basic block when variable is referenced through non-changing frame
+# pointer register. Having BB1 that branches to BB2 and BB3, where
+# BB2 falls through to BB3, variable can have different locations at BB1 and BB2.
+# Since input locations at BB3 for same variable are different LiveDebugValues
+# wont generate DBG_VALUE for BB3. If last variable location at BB2 is
+# non-changing register, DbgEntityHistoryCalculator will extend range of
+# DBG_VALUE from BB2 to whole BB3 and thus produce incorrect range for
+# case when we took branch BB3 from BB1.
+#
+# Verifies that "local1" stack location is ended at the end of the block (.Ltmp6).
+#
+# CHECK: .Ltmp4:
+# CHECK-NEXT:   #DEBUG_VALUE: foo:local1 <- [DW_OP_constu 4, DW_OP_minus, DW_OP_deref] $rbp
+# CHECK:        jmp     .LBB0_2
+# CHECK-NEXT: .Ltmp6:
+# CHECK: .Lfunc_end0:
+#
+# CHECK: .Linfo_string7:
+# CHECK-NEXT: .asciz  "local1"
+#
+# CHECK: .Ldebug_loc2:
+# CHECK-NEXT: .quad   .Ltmp1-.Lfunc_begin0
+# CHECK-NEXT: .quad   .Ltmp4-.Lfunc_begin0
+# CHECK-NEXT: .short  1                       # Loc expr size
+# CHECK-NEXT: .byte   94                      # super-register DW_OP_reg14
+# CHECK-NEXT: .quad   .Ltmp4-.Lfunc_begin0
+# CHECK-NEXT: .quad   .Ltmp6-.Lfunc_begin0
+# CHECK-NEXT: .short  2                       # Loc expr size
+# CHECK-NEXT: .byte   118                     # DW_OP_breg6
+# CHECK-NEXT: .byte   124                     # -4
+#
+# CHECK: .long   .Ldebug_loc2            # DW_AT_location
+# CHECK-NEXT: .long   .Linfo_string7          # DW_AT_name
+
+
+--- |
+  ; ModuleID = 'dbg-stack-value-range.ll'
+  source_filename = "dbg-stack-value-range.c"
+  target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+  target triple = "x86_64-unknown-linux-gnu"
+  
+  ; Function Attrs: nounwind uwtable
+  define dso_local i32 @foo(i32 %X) local_unnamed_addr #0 !dbg !7 {
+  entry:
+    %local1 = alloca i32, align 4
+    call void @llvm.dbg.value(metadata i32 %X, metadata !12, metadata !DIExpression()), !dbg !15
+    %0 = bitcast i32* %local1 to i8*, !dbg !15
+    call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %0), !dbg !15
+    call void @llvm.dbg.value(metadata i32 5, metadata !14, metadata !DIExpression()), !dbg !15
+    %call = tail call i32 (...) @check(), !dbg !15
+    %tobool = icmp eq i32 %call, 0, !dbg !15
+    br i1 %tobool, label %if.else, label %if.then, !dbg !15
+  
+  if.then:                                          ; preds = %entry
+    call void @llvm.dbg.value(metadata i32 4, metadata !13, metadata !DIExpression()), !dbg !15
+    store i32 4, i32* %local1, align 4, !dbg !15, !tbaa !16
+    call void @llvm.dbg.value(metadata i32* %local1, metadata !13, metadata !DIExpression(DW_OP_deref)), !dbg !15
+    %call1 = call i32 @init(i32* nonnull %local1), !dbg !15
+    call void @llvm.dbg.value(metadata i32 undef, metadata !14, metadata !DIExpression()), !dbg !15
+    br label %if.end, !dbg !15
+  
+  if.else:                                          ; preds = %entry
+    call void @llvm.dbg.value(metadata i32 5, metadata !13, metadata !DIExpression()), !dbg !15
+    store i32 5, i32* %local1, align 4, !dbg !15, !tbaa !16
+    br label %if.end
+  
+  if.end:                                           ; preds = %if.else, %if.then
+    %1 = bitcast i32* %local1 to i8*, !dbg !15
+    call void @llvm.dbg.value(metadata i32 undef, metadata !14, metadata !DIExpression()), !dbg !15
+    %call2 = call i32 (...) @init2(), !dbg !15
+    call void @llvm.dbg.value(metadata i32 undef, metadata !14, metadata !DIExpression()), !dbg !15
+    %2 = load i32, i32* %local1, align 4, !dbg !15, !tbaa !16
+    call void @llvm.dbg.value(metadata i32 %2, metadata !13, metadata !DIExpression()), !dbg !15
+    call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %1), !dbg !15
+    ret i32 %2, !dbg !15
+  }
+  
+  ; Function Attrs: argmemonly nounwind
+  declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture)
+  
+  declare dso_local i32 @check(...) local_unnamed_addr
+  
+  declare dso_local i32 @init(i32*) local_unnamed_addr
+  
+  declare dso_local i32 @init2(...) local_unnamed_addr
+  
+  ; Function Attrs: argmemonly nounwind
+  declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture)
+  
+  ; Function Attrs: nounwind readnone speculatable
+  declare void @llvm.dbg.value(metadata, metadata, metadata)
+  
+  ; Function Attrs: nounwind
+  declare void @llvm.stackprotector(i8*, i8**)
+
+  attributes #0 = { nounwind uwtable "no-frame-pointer-elim"="false" "no-frame-pointer-elim-non-leaf" }
+  
+  !llvm.dbg.cu = !{!0}
+  !llvm.module.flags = !{!3, !4, !5}
+  !llvm.ident = !{!6}
+  
+  !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 9.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+  !1 = !DIFile(filename: "dbg-stack-value-range.c", directory: "/")
+  !2 = !{}
+  !3 = !{i32 2, !"Dwarf Version", i32 4}
+  !4 = !{i32 2, !"Debug Info Version", i32 3}
+  !5 = !{i32 1, !"wchar_size", i32 4}
+  !6 = !{!"clang version 9.0.0"}
+  !7 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 11, type: !8, scopeLine: 11, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !11)
+  !8 = !DISubroutineType(types: !9)
+  !9 = !{!10, !10}
+  !10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+  !11 = !{!12, !13, !14}
+  !12 = !DILocalVariable(name: "X", arg: 1, scope: !7, file: !1, line: 11, type: !10)
+  !13 = !DILocalVariable(name: "local1", scope: !7, file: !1, line: 12, type: !10)
+  !14 = !DILocalVariable(name: "local2", scope: !7, file: !1, line: 12, type: !10)
+  !15 = !DILocation(line: 11, column: 13, scope: !7)
+  !16 = !{!17, !17, i64 0}
+  !17 = !{!"int", !18, i64 0}
+  !18 = !{!"omnipotent char", !19, i64 0}
+  !19 = !{!"Simple C/C++ TBAA"}
+
+...
+---
+name:            foo
+alignment:       4
+frameInfo:       
+  stackSize:       24
+  offsetAdjustment: -24
+  maxAlignment:    4
+  adjustsStack:    true
+  hasCalls:        true
+fixedStack:      
+  - { id: 0, type: spill-slot, offset: -16, size: 8, alignment: 16, stack-id: 0, 
+      callee-saved-register: '$r14d', callee-saved-restored: true, debug-info-variable: '', 
+      debug-info-expression: '', debug-info-location: '' }
+stack:           
+  - { id: 0, name: local1, type: default, offset: -20, size: 4, alignment: 4, 
+      stack-id: 0, callee-saved-register: '', callee-saved-restored: true, 
+      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
+body:             |
+  bb.0.entry:
+    successors: %bb.3(0x30000000), %bb.1(0x50000000)
+  
+    DBG_VALUE $edi, $noreg, !12, !DIExpression(), debug-location !15
+    frame-setup PUSH64r killed $rbp, implicit-def $rsp, implicit $rsp
+    CFI_INSTRUCTION def_cfa_offset 16
+    CFI_INSTRUCTION offset $rbp, -16
+    $rbp = frame-setup MOV64rr $rsp
+    CFI_INSTRUCTION def_cfa_register $rbp
+    $rsp = frame-setup SUB64ri8 $rsp, 16, implicit-def dead $eflags
+    DBG_VALUE 5, $noreg, !14, !DIExpression(), debug-location !15
+    $r14d = MOV32ri 4, implicit-def $r14
+    DBG_VALUE $r14d, $noreg, !13, !DIExpression(), debug-location !15
+    dead $eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, implicit-def $al, debug-location !15
+    CALL64pcrel32 @check, csr_64, implicit $rsp, implicit $ssp, implicit $al, implicit-def $rsp, implicit-def $ssp, implicit-def $eax, debug-location !15
+    TEST32rr killed renamable $eax, renamable $eax, implicit-def $eflags, debug-location !15
+    JCC_1 %bb.3, 4, implicit killed $eflags, debug-location !15
+  
+  bb.1.if.then:
+    successors: %bb.3(0x80000000)
+  
+    MOV32mr $rbp, 1, $noreg, -4, $noreg, $r14d, debug-location !15 :: (store 4 into %ir.local1, !tbaa !16)
+    DBG_VALUE $rbp, $noreg, !13, !DIExpression(DW_OP_constu, 4, DW_OP_minus, DW_OP_deref), debug-location !15
+    renamable $rdi = LEA64r $rbp, 1, $noreg, -4, $noreg
+    CALL64pcrel32 @init, csr_64, implicit $rsp, implicit $ssp, implicit $rdi, implicit-def $rsp, implicit-def $ssp, implicit-def dead $eax, debug-location !15
+    DBG_VALUE $noreg, $noreg, !14, !DIExpression(), debug-location !15
+    JMP_1 %bb.3
+  
+  bb.3.if.end:
+    DBG_VALUE $noreg, $noreg, !14, !DIExpression(), debug-location !15
+    dead $eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, implicit-def $al, debug-location !15
+    CALL64pcrel32 @init2, csr_64, implicit $rsp, implicit $ssp, implicit $al, implicit-def $rsp, implicit-def $ssp, implicit-def dead $eax, debug-location !15
+    DBG_VALUE $noreg, $noreg, !14, !DIExpression(), debug-location !15
+    renamable $eax = MOV32rm $rbp, 1, $noreg, -4, $noreg, debug-location !15 :: (dereferenceable load 4 from %ir.local1, !tbaa !16)
+    $rsp = frame-destroy ADD64ri8 $rsp, 16, implicit-def dead $eflags, debug-location !15
+    $rbp = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !15
+    CFI_INSTRUCTION def_cfa $rsp, 8, debug-location !15
+    RETQ $eax, debug-location !15
+
+...
diff --git a/llvm/test/DebugInfo/X86/fission-ranges.ll b/llvm/test/DebugInfo/X86/fission-ranges.ll
index e4347736195..fa911cd60f6 100644
--- a/llvm/test/DebugInfo/X86/fission-ranges.ll
+++ b/llvm/test/DebugInfo/X86/fission-ranges.ll
@@ -161,7 +161,7 @@ for.inc10:                                        ; preds = %for.body9
 
 for.inc13:                                        ; preds = %for.inc10
   %inc14 = add i32 %d.06, 1, !dbg !37
-  tail call void @llvm.dbg.value(metadata i32 %inc14, metadata !16, metadata !DIExpression()), !dbg !37
+  tail call void @llvm.dbg.value(metadata i32 %inc14, metadata !16, metadata !DIExpression()), !dbg !42
   %exitcond12 = icmp eq i32 %inc14, 30, !dbg !37
   br i1 %exitcond12, label %for.inc16, label %for.cond4.preheader, !dbg !37