[PATCH] D153855: [StructuralHash] Ignore global variable declarations

[Mikael Holmén via Phabricator via llvm-commits]

uabelho created this revision.
uabelho added reviewers: aeubanks, nikic.
Herald added subscribers: StephenFan, bjope, hiraditya.
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Ignore declarations of global variables, just as we do with declarations
of functions.

Done as a follow up to the comments in https://reviews.llvm.org/D149209.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D153855

Files:
  llvm/lib/IR/StructuralHash.cpp
  llvm/test/Transforms/StripDeadPrototypes/remove-global-variable-declaration.ll


Index: llvm/test/Transforms/StripDeadPrototypes/remove-global-variable-declaration.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/StripDeadPrototypes/remove-global-variable-declaration.ll
@@ -0,0 +1,38 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+; RUN: opt -passes=strip-dead-prototypes -S -verify-analysis-invalidation < %s | FileCheck %s
+
+; The declaration of the unused global variable @.str should be removed without
+; getting any error from -verify-analysis-invalidation.
+
+; CHECK-NOT: @.str
+
+ at .str = external constant [15 x i16]
+
+define i16 @_Z7test_itv() {
+; CHECK-LABEL: define i16 @_Z7test_itv() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0(i64 0, ptr null)
+; CHECK-NEXT:    call void @llvm.dbg.declare(metadata ptr null, metadata [[META3:![0-9]+]], metadata !DIExpression()), !dbg [[DBG5:![0-9]+]]
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0(i64 0, ptr null)
+; CHECK-NEXT:    ret i16 0
+;
+entry:
+  call void @llvm.lifetime.start.p0(i64 0, ptr null)
+  call void @llvm.dbg.declare(metadata ptr null, metadata !3, metadata !DIExpression()), !dbg !5
+  call void @llvm.lifetime.end.p0(i64 0, ptr null)
+  ret i16 0
+}
+
+declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture)
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+declare void @llvm.lifetime.end.p0(i64 immarg, ptr nocapture)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1)
+!1 = !DIFile(filename: "t.C", directory: "/")
+!2 = !{i32 2, !"Debug Info Version", i32 3}
+!3 = !DILocalVariable(scope: !4)
+!4 = distinct !DISubprogram(unit: !0)
+!5 = !DILocation(scope: !4)
Index: llvm/lib/IR/StructuralHash.cpp
===================================================================
--- llvm/lib/IR/StructuralHash.cpp
+++ llvm/lib/IR/StructuralHash.cpp
@@ -58,8 +58,9 @@
   }
 
   void update(const GlobalVariable &GV) {
-    // used/compiler.used don't affect analyses.
-    if (GV.getName() == "llvm.compiler.used" || GV.getName() == "llvm.used")
+    // Declarations and used/compiler.used don't affect analyses.
+    if (GV.isDeclaration() || GV.getName() == "llvm.compiler.used" ||
+        GV.getName() == "llvm.used")
       return;
     hash(23456); // Global header
     hash(GV.getValueType()->getTypeID());


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