[PATCH] D131179: [StripDeadDebugInfo] Drop dead CUs for const global expression

Thu Aug 4 09:18:26 PDT 2022

bader created this revision.
bader added reviewers: loladiro, aprantl, dexonsmith, probinson, mlychkov.
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Compile units are not left explicitly if they have const global
expression.  They should be left if that const global is used in a
function that is contained in extracted module.

Signed-off-by: Mikhail Lychkov <mikhail.lychkov at intel.com>


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D131179

Files:
  llvm/lib/Transforms/IPO/StripSymbols.cpp
  llvm/test/Transforms/StripSymbols/strip-cu-with-const-gve.ll
  llvm/test/Transforms/StripSymbols/strip-dead-debug-info.ll


Index: llvm/test/Transforms/StripSymbols/strip-dead-debug-info.ll
===================================================================

--- llvm/test/Transforms/StripSymbols/strip-dead-debug-info.ll
+++ llvm/test/Transforms/StripSymbols/strip-dead-debug-info.ll
@@ -4,9 +4,10 @@
 ; CHECK-NOT: "bar"
 ; CHECK-NOT: "abcd"
 ; CHECK-NOT: "GCC"
-; CHECK: "Globals"
-; CHECK: "abcd2"
-; CHECK: "abcd3"
+; CHECK-NOT: "Globals"
+; CHECK-NOT: "abcd2"
+; CHECK-NOT: "abcd3"
+; CHECK: "InlineTest"
 
 source_filename = "test/Transforms/StripSymbols/strip-dead-debug-info.ll"
 
Index: llvm/test/Transforms/StripSymbols/strip-cu-with-const-gve.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/StripSymbols/strip-cu-with-const-gve.ll
@@ -0,0 +1,61 @@
+; This test checks that strip-dead-debug-info pass deletes debug compile units
+; if global constants from those units are absent in split module.
+
+; RUN: opt -passes='strip-dead-debug-info,verify' %s -S | FileCheck %s
+
+; CHECK: !llvm.dbg.cu = !{!{{[0-9]+}}, !{{[0-9]+}}}
+; CHECK-COUNT-2: !DICompileUnit
+
+;target datalayout = "e-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-n8:16:32:64"
+;target triple = "spir64-unknown-unknown"
+
+; Function Attrs: convergent nounwind
+define void @dev_func1() #0 !dbg !16 {
+  %1 = call i32 @dev_subfunc1(i32 0) #1, !dbg !19
+  ret void, !dbg !20
+}
+
+; Function Attrs: convergent nounwind
+define i32 @dev_subfunc1(i32 %0) #0 !dbg !21 {
+  ret i32 %0, !dbg !24
+}
+
+; Function Attrs: convergent nounwind
+define void @dev_func2() #0 !dbg !25 {
+  ret void, !dbg !26
+}
+
+attributes #0 = { convergent nounwind }
+attributes #1 = { convergent }
+
+!llvm.dbg.cu = !{!0, !8, !10}
+!llvm.module.flags = !{!15}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3, imports: !2, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "dev_func1.cpp", directory: "/home/usr/test")
+!2 = !{}
+!3 = !{!4}
+!4 = !DIGlobalVariableExpression(var: !5, expr: !DIExpression(DW_OP_constu, 0, DW_OP_stack_value))
+!5 = distinct !DIGlobalVariable(name: "ZERO", scope: !1, file: !1, line: 32, type: !6, isLocal: true, isDefinition: true)
+!6 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !7)
+!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!8 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !9, isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, imports: !2, splitDebugInlining: false, nameTableKind: None)
+!9 = !DIFile(filename: "dev_func2.cpp", directory: "/home/usr/test")
+!10 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !11, isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !12, imports: !2, splitDebugInlining: false, nameTableKind: None)
+!11 = !DIFile(filename: "file3.cpp", directory: "/home/usr/test")
+!12 = !{!13}
+!13 = !DIGlobalVariableExpression(var: !14, expr: !DIExpression(DW_OP_constu, 0, DW_OP_stack_value))
+!14 = distinct !DIGlobalVariable(name: "ZERO", scope: !11, file: !11, line: 145, type: !6, isLocal: true, isDefinition: true)
+!15 = !{i32 2, !"Debug Info Version", i32 3}
+!16 = distinct !DISubprogram(name: "dev_func1", linkageName: "dev_func1", scope: !1, file: !1, line: 22, type: !17, scopeLine: 22, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!17 = !DISubroutineType(types: !18)
+!18 = !{null}
+!19 = !DILocation(line: 12, column: 1, scope: !16)
+!20 = !DILocation(line: 29, column: 5, scope: !16)
+!21 = distinct !DISubprogram(name: "dev_subfunc1", linkageName: "dev_subfunc1", scope: !1, file: !1, line: 42, type: !22, scopeLine: 42, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!22 = !DISubroutineType(types: !23)
+!23 = !{!7, !7}
+!24 = !DILocation(line: 5, column: 1, scope: !21)
+!25 = distinct !DISubprogram(name: "dev_func2", linkageName: "dev_func2", scope: !9, file: !9, line: 22, type: !17, scopeLine: 22, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !8, retainedNodes: !2)
+!26 = !DILocation(line: 29, column: 5, scope: !25)
+
Index: llvm/lib/Transforms/IPO/StripSymbols.cpp
===================================================================
--- llvm/lib/Transforms/IPO/StripSymbols.cpp
+++ llvm/lib/Transforms/IPO/StripSymbols.cpp
@@ -333,9 +333,6 @@
     // Create our live global variable list.
     bool GlobalVariableChange = false;
     for (auto *DIG : DIC->getGlobalVariables()) {
-      if (DIG->getExpression() && DIG->getExpression()->isConstant())
-        LiveGVs.insert(DIG);
-
       // Make sure we only visit each global variable only once.
       if (!VisitedSet.insert(DIG).second)
         continue;


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