[DebugInfo] Correctly handle salvaged casts and split fragments at ISel

Previously, LLVM had no functional way of performing casts inside of a
DIExpression(), which made salvaging cast instructions other than Noop
casts impossible. This patch enables the salvaging of casts by using the
DW_OP_LLVM_convert operator for SExt and Trunc instructions.

There is another issue which is exposed by this fix, in which fragment
DIExpressions (which are preserved more readily by this patch) for
values that must be split across registers in ISel trigger an assertion,
as the 'split' fragments extend beyond the bounds of the fragment
DIExpression causing an error. This patch also fixes this issue by
checking the fragment status of DIExpressions which are to be split, and
dropping fragments that are invalid.

7 files changed, 106 insertions, 8 deletions

diff --git a/llvm/test/CodeGen/ARM/fragmented-args-multiple-regs.ll b/llvm/test/CodeGen/ARM/fragmented-args-multiple-regs.ll
new file mode 100644
index 00000000000..8c4822dfe15
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/fragmented-args-multiple-regs.ll
@@ -0,0 +1,72 @@
+; RUN: llc < %s -mtriple=armv7-linux-gnueabihf -O1 -stop-after=finalize-isel | FileCheck %s
+
+define dso_local i32 @h(i64 %j) local_unnamed_addr !dbg !8 {
+entry:
+  call void @llvm.dbg.value(metadata i64 %j, metadata !14, metadata !DIExpression()), !dbg !29
+  call void @llvm.dbg.value(metadata i64 %j, metadata !15, metadata !DIExpression(DW_OP_LLVM_convert, 64, DW_ATE_unsigned, DW_OP_LLVM_convert, 32, DW_ATE_unsigned, DW_OP_stack_value, DW_OP_LLVM_fragment, 0, 32)), !dbg !29
+  call void @llvm.dbg.value(metadata i64 %j, metadata !15, metadata !DIExpression(DW_OP_constu, 32, DW_OP_shr, DW_OP_LLVM_convert, 64, DW_ATE_unsigned, DW_OP_LLVM_convert, 32, DW_ATE_unsigned, DW_OP_stack_value, DW_OP_LLVM_fragment, 32, 32)), !dbg !29
+  %tobool = icmp ult i64 %j, 4294967296, !dbg !30
+  br i1 %tobool, label %cleanup, label %if.then, !dbg !31
+
+if.then:                                          ; preds = %entry
+  call void @llvm.dbg.value(metadata i64 %j, metadata !15, metadata !DIExpression(DW_OP_LLVM_convert, 64, DW_ATE_unsigned, DW_OP_LLVM_convert, 32, DW_ATE_unsigned, DW_OP_stack_value, DW_OP_LLVM_fragment, 0, 32)), !dbg !29
+  %conv = sitofp i64 %j to double, !dbg !32
+  %add = fadd double %conv, 0x43F0000000000000, !dbg !33
+  call void @llvm.dbg.value(metadata double %add, metadata !25, metadata !DIExpression()), !dbg !34
+  %conv2 = fptosi double %add to i32, !dbg !35
+  br label %cleanup
+
+cleanup:                                          ; preds = %entry, %if.then
+  %retval.0 = phi i32 [ %conv2, %if.then ], [ undef, %entry ]
+  ret i32 %retval.0, !dbg !36
+}
+
+; CHECK-LABEL: bb.0.entry:
+; CHECK: DBG_VALUE [[REG1:%[0-9]+]], $noreg, !14, !DIExpression(DW_OP_LLVM_fragment, 32, 32
+; CHECK: DBG_VALUE [[REG2:%[0-9]+]], $noreg, !14, !DIExpression(DW_OP_LLVM_fragment, 0, 32
+; CHECK: DBG_VALUE [[REG2]], $noreg, !15, !DIExpression({{.+}}DW_OP_LLVM_fragment, 0, 32
+; CHECK: DBG_VALUE $noreg, $noreg, !15, !DIExpression({{.+}}DW_OP_LLVM_fragment, 32, 32
+
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 10.0.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "tif_aux.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{i32 1, !"min_enum_size", i32 4}
+!7 = !{!"clang version 10.0.0 "}
+!8 = distinct !DISubprogram(name: "h", scope: !1, file: !1, line: 10, type: !9, scopeLine: 10, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !13)
+!9 = !DISubroutineType(types: !10)
+!10 = !{!11, !12}
+!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!12 = !DIBasicType(name: "long long int", size: 64, encoding: DW_ATE_signed)
+!13 = !{!14, !15, !25}
+!14 = !DILocalVariable(name: "j", arg: 1, scope: !8, file: !1, line: 10, type: !12)
+!15 = !DILocalVariable(name: "i", scope: !8, file: !1, line: 11, type: !16)
+!16 = !DIDerivedType(tag: DW_TAG_typedef, name: "g", file: !1, line: 8, baseType: !17)
+!17 = distinct !DICompositeType(tag: DW_TAG_union_type, file: !1, line: 5, size: 64, elements: !18)
+!18 = !{!19, !24}
+!19 = !DIDerivedType(tag: DW_TAG_member, name: "e", scope: !17, file: !1, line: 6, baseType: !20, size: 64)
+!20 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "b", file: !1, line: 1, size: 64, elements: !21)
+!21 = !{!22, !23}
+!22 = !DIDerivedType(tag: DW_TAG_member, name: "c", scope: !20, file: !1, line: 2, baseType: !11, size: 32)
+!23 = !DIDerivedType(tag: DW_TAG_member, name: "d", scope: !20, file: !1, line: 2, baseType: !11, size: 32, offset: 32)
+!24 = !DIDerivedType(tag: DW_TAG_member, name: "f", scope: !17, file: !1, line: 7, baseType: !12, size: 64)
+!25 = !DILocalVariable(name: "a", scope: !26, file: !1, line: 14, type: !28)
+!26 = distinct !DILexicalBlock(scope: !27, file: !1, line: 13, column: 14)
+!27 = distinct !DILexicalBlock(scope: !8, file: !1, line: 13, column: 7)
+!28 = !DIBasicType(name: "double", size: 64, encoding: DW_ATE_float)
+!29 = !DILocation(line: 0, scope: !8)
+!30 = !DILocation(line: 13, column: 7, scope: !27)
+!31 = !DILocation(line: 13, column: 7, scope: !8)
+!32 = !DILocation(line: 14, column: 16, scope: !26)
+!33 = !DILocation(line: 14, column: 20, scope: !26)
+!34 = !DILocation(line: 0, scope: !26)
+!35 = !DILocation(line: 15, column: 12, scope: !26)
+!36 = !DILocation(line: 17, column: 1, scope: !8)
diff --git a/llvm/test/DebugInfo/X86/dbg-value-dropped-instcombine.ll b/llvm/test/DebugInfo/X86/dbg-value-dropped-instcombine.ll
index 18e51b6fabd..46f940e11c6 100644
--- a/llvm/test/DebugInfo/X86/dbg-value-dropped-instcombine.ll
+++ b/llvm/test/DebugInfo/X86/dbg-value-dropped-instcombine.ll
@@ -21,8 +21,8 @@
 ; }
 
 ; CHECK: define dso_local i64 @foo
-; CHECK: @llvm.dbg.value({{.*}}, metadata ![[BEE:[0-9]+]], metadata !DIExpression(DW_OP_LLVM_fragment, 0, 32)),
-; CHECK: @llvm.dbg.value(metadata i32 undef, metadata ![[BEE]], metadata !DIExpression(DW_OP_LLVM_fragment, 32, 32)),
+; CHECK: @llvm.dbg.value(metadata i64 {{.*}}, metadata ![[BEE:[0-9]+]], metadata !DIExpression(DW_OP_LLVM_fragment, 0, 32)),
+; CHECK: @llvm.dbg.value(metadata i64 {{.*}}, metadata ![[BEE]], metadata !DIExpression({{.*}}, DW_OP_LLVM_fragment, 32, 32)),
 
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-unknown"
diff --git a/llvm/test/DebugInfo/salvage-cast-debug-info.ll b/llvm/test/DebugInfo/salvage-cast-debug-info.ll
new file mode 100644
index 00000000000..f39ac46a66a
--- /dev/null
+++ b/llvm/test/DebugInfo/salvage-cast-debug-info.ll
@@ -0,0 +1,25 @@
+; RUN: opt %s -debugify -early-cse -S | FileCheck %s
+define i32 @foo(i64 %nose, i32 %more) {
+; CHECK-LABEL: @foo(
+; CHECK: call void @llvm.dbg.value(metadata i64 %nose, metadata [[V1:![0-9]+]], metadata !DIExpression(DW_OP_LLVM_convert, 64, DW_ATE_unsigned, DW_OP_LLVM_convert, 32, DW_ATE_unsigned
+; CHECK: call void @llvm.dbg.value(metadata i64 %nose.shift, metadata [[V2:![0-9]+]]
+; CHECK: call void @llvm.dbg.value(metadata i64 %nose.shift, metadata [[V3:![0-9]+]], metadata !DIExpression(DW_OP_LLVM_convert, 64, DW_ATE_unsigned, DW_OP_LLVM_convert, 32, DW_ATE_unsigned
+
+entry:
+  %nose.trunc = trunc i64 %nose to i32
+  %nose.shift = lshr i64 %nose, 32
+  %nose.trunc.2 = trunc i64 %nose.shift to i32
+  %add = add nsw i32 %more, 1
+  ret i32 %add
+}
+
+!llvm.module.flags = !{!0, !1}
+!llvm.ident = !{!2}
+
+!0 = !{i32 1, !"wchar_size", i32 2}
+!1 = !{i32 7, !"PIC Level", i32 2}
+!2 = !{!"clang version 10.0.0 "}
+
+; CHECK: [[V1]] = !DILocalVariable(
+; CHECK: [[V2]] = !DILocalVariable(
+; CHECK: [[V3]] = !DILocalVariable(
diff --git a/llvm/test/Transforms/EarlyCSE/debug-info-undef.ll b/llvm/test/Transforms/EarlyCSE/debug-info-undef.ll
index 4615aa264b6..b0fb8ff75ad 100644
--- a/llvm/test/Transforms/EarlyCSE/debug-info-undef.ll
+++ b/llvm/test/Transforms/EarlyCSE/debug-info-undef.ll
@@ -10,7 +10,7 @@ entry:
   %0 = load i8, i8* @a, align 1, !dbg !19, !tbaa !20
   %conv = sext i8 %0 to i16, !dbg !19
 
-; CHECK: call void @llvm.dbg.value(metadata i16 undef, metadata !17, metadata !DIExpression()), !dbg !18
+; CHECK: call void @llvm.dbg.value(metadata i8 %0, metadata !17, metadata !DIExpression(DW_OP_LLVM_convert, 8, DW_ATE_signed, DW_OP_LLVM_convert, 16, DW_ATE_signed, DW_OP_stack_value)), !dbg !18
 ; CHECK-NEXT:  call i32 (...) @optimize_me_not()
 
   call void @llvm.dbg.value(metadata i16 %conv, metadata !17, metadata !DIExpression()), !dbg !18
diff --git a/llvm/test/Transforms/InstCombine/cast-mul-select.ll b/llvm/test/Transforms/InstCombine/cast-mul-select.ll
index 5de3314b472..f82d2fd285f 100644
--- a/llvm/test/Transforms/InstCombine/cast-mul-select.ll
+++ b/llvm/test/Transforms/InstCombine/cast-mul-select.ll
@@ -13,8 +13,8 @@ define i32 @mul(i32 %x, i32 %y) {
 ; we preserve the debug information in the resulting
 ; instruction.
 ; DBGINFO-LABEL: @mul(
-; DBGINFO-NEXT:    call void @llvm.dbg.value(metadata i8 undef
-; DBGINFO-NEXT:    call void @llvm.dbg.value(metadata i8 undef
+; DBGINFO-NEXT:    call void @llvm.dbg.value(metadata i32 %x
+; DBGINFO-NEXT:    call void @llvm.dbg.value(metadata i32 %y
 ; DBGINFO-NEXT:    [[C:%.*]] = mul i32 {{.*}}
 ; DBGINFO-NEXT:    [[D:%.*]] = and i32 {{.*}}
 ; DBGINFO-NEXT:    call void @llvm.dbg.value(metadata i32 [[C]]
diff --git a/llvm/test/Transforms/InstCombine/pr43893.ll b/llvm/test/Transforms/InstCombine/pr43893.ll
index 0eb926b19a6..5eaae20fe74 100644
--- a/llvm/test/Transforms/InstCombine/pr43893.ll
+++ b/llvm/test/Transforms/InstCombine/pr43893.ll
@@ -13,9 +13,10 @@ entry:
 ;CHECK: call void @llvm.dbg.value(metadata i32 -8
 ;CHECK: call void @llvm.dbg.value(metadata i32 undef
   %conv = sext i8 %dec to i32, !dbg !17
-  call void @llvm.dbg.value(metadata i32 %conv, metadata !18, metadata !DIExpression()), !dbg !19
+  %udiv = udiv i32 %conv, 4, !dbg !17
+  call void @llvm.dbg.value(metadata i32 %udiv, metadata !18, metadata !DIExpression()), !dbg !19
   call void @llvm.dbg.value(metadata i32 -8, metadata !20, metadata !DIExpression()), !dbg !19
-  call void @llvm.dbg.value(metadata i32 %conv, metadata !20, metadata !DIExpression()), !dbg !19
+  call void @llvm.dbg.value(metadata i32 %udiv, metadata !20, metadata !DIExpression()), !dbg !19
   store i8 0, i8* @b, align 1, !dbg !21
   %cmp = icmp sgt i32 %conv, 0, !dbg !22
   %conv1 = zext i1 %cmp to i32, !dbg !22
diff --git a/llvm/test/Transforms/InstCombine/unavailable-debug.ll b/llvm/test/Transforms/InstCombine/unavailable-debug.ll
index 703c1c2898f..e3f0d7cf22d 100644
--- a/llvm/test/Transforms/InstCombine/unavailable-debug.ll
+++ b/llvm/test/Transforms/InstCombine/unavailable-debug.ll
@@ -2,7 +2,7 @@
 
 ; Make sure to update the debug value after dead code elimination.
 ; CHECK: %call = call signext i8 @b(i32 6), !dbg !39
-; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 undef, metadata !30, metadata !DIExpression()), !dbg !38
+; CHECK-NEXT: call void @llvm.dbg.value(metadata i8 %call, metadata !30, metadata !DIExpression(DW_OP_LLVM_convert, 8, DW_ATE_signed, DW_OP_LLVM_convert, 32, DW_ATE_signed, DW_OP_stack_value)), !dbg !38
 
 @e = common local_unnamed_addr global i8 0, align 1, !dbg !0
 @c = common local_unnamed_addr global i32 0, align 4, !dbg !6