[PATCH] D27471: [BDCE/DebugInfo] Preserve llvm.dbg.value's argument

[Davide Italiano via Phabricator via llvm-commits]

davide updated this revision to Diff 80468.
davide added a comment.

Address Eli's comment.


https://reviews.llvm.org/D27471

Files:
  lib/Transforms/Scalar/BDCE.cpp
  test/Transforms/BDCE/pr26587.ll


Index: test/Transforms/BDCE/pr26587.ll
===================================================================
--- /dev/null
+++ test/Transforms/BDCE/pr26587.ll
@@ -0,0 +1,46 @@
+; Test that BDCE doesn't destroy llvm.dbg.value's argument.
+; RUN: opt -bdce %s -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; CHECK: define void @f()
+; CHECK-NEXT: entry:
+; CHECK-NEXT: tail call void (...) @h()
+; CHECK-NEXT: %[[CALL:.*]] = tail call i32 (...) @g()
+; CHECK-NEXT: tail call void @llvm.dbg.value(metadata i32 %[[CALL:.*]]
+
+define void @f() !dbg !6 {
+entry:
+  tail call void (...) @h(), !dbg !9
+  %call = tail call i32 (...) @g(), !dbg !10
+  tail call void @llvm.dbg.value(metadata i32 %call, i64 0, metadata !11, metadata !13), !dbg !14
+  tail call void (...) @h(), !dbg !15
+  ret void, !dbg !16
+}
+
+declare void @h(...)
+declare i32 @g(...)
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+!llvm.ident = !{!5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 4.0.0 (trunk 288665) (llvm/trunk 288725)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "patatino.c", directory: "/home/davide/work/llvm/build-clang/bin")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{!"clang version 4.0.0 (trunk 288665) (llvm/trunk 288725)"}
+!6 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 3, type: !7, isLocal: false, isDefinition: true, scopeLine: 3, isOptimized: false, unit: !0, variables: !2)
+!7 = !DISubroutineType(types: !8)
+!8 = !{null}
+!9 = !DILocation(line: 4, column: 3, scope: !6)
+!10 = !DILocation(line: 5, column: 11, scope: !6)
+!11 = !DILocalVariable(name: "a", scope: !6, file: !1, line: 5, type: !12)
+!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!13 = !DIExpression()
+!14 = !DILocation(line: 5, column: 7, scope: !6)
+!15 = !DILocation(line: 6, column: 3, scope: !6)
+!16 = !DILocation(line: 7, column: 1, scope: !6)
Index: lib/Transforms/Scalar/BDCE.cpp
===================================================================
--- lib/Transforms/Scalar/BDCE.cpp
+++ lib/Transforms/Scalar/BDCE.cpp
@@ -39,6 +39,11 @@
   SmallVector<Instruction*, 128> Worklist;
   bool Changed = false;
   for (Instruction &I : instructions(F)) {
+    // If the instruction has side effects and no non-dbg uses,
+    // BDCE should skip it.
+    if (I.mayHaveSideEffects() && I.use_empty())
+      continue;
+
     if (I.getType()->isIntegerTy() &&
         !DB.getDemandedBits(&I).getBoolValue()) {
       // For live instructions that have all dead bits, first make them dead by


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