Revert "[llvm] Teach GlobalDCE about dso_local_equivalent"

This reverts commit 86dbcaf.

Reverting since this depends on db28818
which broke our lto builders reported by fxbug.dev/12380.

llvm/include/llvm/Analysis/TypeMetadataUtils.h

@@ -78,8 +78,8 @@ Constant *getPointerAtOffset(Constant *I, uint64_t Offset, Module &M,
                              Constant *TopLevelGlobal = nullptr);
 
 /// Finds the same "relative pointer" pattern as described above, where the
-/// target is `C`, and replaces the entire pattern with a constant zero.
-void replaceRelativePointerUsersWithZero(Constant *C);
+/// target is `F`, and replaces the entire pattern with a constant zero.
+void replaceRelativePointerUsersWithZero(Function *F);
 
 } // namespace llvm
 

llvm/lib/Analysis/TypeMetadataUtils.cpp

@@ -199,26 +199,19 @@ Constant *llvm::getPointerAtOffset(Constant *I, uint64_t Offset, Module &M,
   return nullptr;
 }
 
-static void replaceRelativePointerUserWithZero(User *U) {
-  auto *PtrExpr = dyn_cast<ConstantExpr>(U);
-  if (!PtrExpr || PtrExpr->getOpcode() != Instruction::PtrToInt)
-    return;
-
-  for (auto *PtrToIntUser : PtrExpr->users()) {
-    auto *SubExpr = dyn_cast<ConstantExpr>(PtrToIntUser);
-    if (!SubExpr || SubExpr->getOpcode() != Instruction::Sub)
-      return;
+void llvm::replaceRelativePointerUsersWithZero(Function *F) {
+  for (auto *U : F->users()) {
+    auto *PtrExpr = dyn_cast<ConstantExpr>(U);
+    if (!PtrExpr || PtrExpr->getOpcode() != Instruction::PtrToInt)
+      continue;
 
-    SubExpr->replaceNonMetadataUsesWith(
-        ConstantInt::get(SubExpr->getType(), 0));
-  }
-}
+    for (auto *PtrToIntUser : PtrExpr->users()) {
+      auto *SubExpr = dyn_cast<ConstantExpr>(PtrToIntUser);
+      if (!SubExpr || SubExpr->getOpcode() != Instruction::Sub)
+        continue;
 
-void llvm::replaceRelativePointerUsersWithZero(Constant *C) {
-  for (auto *U : C->users()) {
-    if (auto *Equiv = dyn_cast<DSOLocalEquivalent>(U))
-      replaceRelativePointerUsersWithZero(Equiv);
-    else
-      replaceRelativePointerUserWithZero(U);
+      SubExpr->replaceNonMetadataUsesWith(
+          ConstantInt::get(SubExpr->getType(), 0));
+    }
   }
 }

llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers-bad.ll

@@ -16,32 +16,14 @@ declare { ptr, i1 } @llvm.type.checked.load(ptr, i32, metadata)
 
 ; CHECK:      @vtable = internal unnamed_addr constant { [3 x i32] } zeroinitializer, align 8, !type !0, !type !1, !vcall_visibility !2
 
-@vtable2 = internal unnamed_addr constant { [3 x i32] } { [3 x i32] [
-  i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vfunc3 to i64), i64 ptrtoint (ptr @vtable2 to i64)) to i32),
-  i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vfunc4 to i64), i64 ptrtoint (ptr @vtable2 to i64)) to i32),
-
-  ; a "bad" relative pointer because it's base is not the @vtable symbol
-  i32 trunc (i64 sub (i64 ptrtoint (ptr @weird_ref_3         to i64), i64 ptrtoint (ptr @weird_ref_4 to i64)) to i32)
-]}, align 4, !type !3, !type !4, !vcall_visibility !{i64 2}
-!3 = !{i64 0, !"vfunc3.type"}
-!4 = !{i64 4, !"vfunc4.type"}
-
-; CHECK:      @vtable2 = internal unnamed_addr constant { [3 x i32] } zeroinitializer, align 4, !type !3, !type !4, !vcall_visibility !2
-
 define internal void @vfunc1() { ret void }
 define internal void @vfunc2() { ret void }
 define internal void @weird_ref_1() { ret void }
 define internal void @weird_ref_2() { ret void }
-declare void @vfunc3()
-declare void @vfunc4()
-declare void @weird_ref_3()
-declare void @weird_ref_4()
 
 define void @main() {
   %1 = ptrtoint ptr @vtable to i64 ; to keep @vtable alive
   call void @weird_ref_2()
-  %2 = ptrtoint ptr @vtable2 to i64 ; to keep @vtable2 alive
-  call void @weird_ref_4()
   ret void
 }
 

llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers-gep.ll

@@ -19,20 +19,6 @@ declare { ptr, i1 } @llvm.type.checked.load(ptr, i32, metadata)
 ; CHECK-SAME:   i32 0
 ; CHECK-SAME: ] }, align 8, !type !0, !type !1, !vcall_visibility !2
 
-@vtable2 = internal unnamed_addr constant { [4 x i32] } { [4 x i32] [
-  i32 42,
-  i32 1337,
-  i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vfunc3_live_extern to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [4 x i32] }, ptr @vtable2, i32 0, i32 0, i32 2) to i64)) to i32),
-  i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vfunc4_dead_extern to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [4 x i32] }, ptr @vtable2, i32 0, i32 0, i32 2) to i64)) to i32)
-]}, align 4, !type !3, !type !4, !vcall_visibility !{i64 2}
-!3 = !{i64 8, !"vfunc3.type"}
-!4 = !{i64 12, !"vfunc4.type"}
-
-; CHECK:      @vtable2 = internal unnamed_addr constant { [4 x i32] } { [4 x i32] [
-; CHECK-SAME:   i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vfunc3_live_extern to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [4 x i32] }, ptr @vtable2, i32 0, i32 0, i32 2) to i64)) to i32),
-; CHECK-SAME:   i32 0
-; CHECK-SAME: ] }, align 4, !type !3, !type !4, !vcall_visibility !2
-
 ; (1) vfunc1_live is referenced from @main, stays alive
 define internal void @vfunc1_live() {
   ; CHECK: define internal void @vfunc1_live(
@@ -45,19 +31,9 @@ define internal void @vfunc2_dead() {
   ret void
 }
 
-; (3) vfunc3_live_extern is referenced from @main, stays alive
-; CHECK: declare void @vfunc3_live_extern
-declare void @vfunc3_live_extern()
-
-; (4) vfunc4_dead_extern is never referenced, gets removed and vtable slot is null'd
-; CHECK-NOT: declare void @vfunc4_dead_extern
-declare void @vfunc4_dead_extern()
-
 define void @main() {
   %1 = ptrtoint ptr @vtable to i64 ; to keep @vtable alive
   %2 = tail call { ptr, i1 } @llvm.type.checked.load(ptr null, i32 0, metadata !"vfunc1.type")
-  %3 = ptrtoint ptr @vtable2 to i64 ; to keep @vtable2 alive
-  %4 = tail call { ptr, i1 } @llvm.type.checked.load(ptr null, i32 0, metadata !"vfunc3.type")
   ret void
 }
 

llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers.ll

@@ -17,20 +17,6 @@ declare { ptr, i1 } @llvm.type.checked.load(ptr, i32, metadata)
 ; CHECK-SAME:   i32 0
 ; CHECK-SAME: ] }, align 8, !type !0, !type !1, !vcall_visibility !2
 
-; Similar to above, but the vtable is more aligned to how C++ relative vtables look.
-; That is, the functions may not be dso-local.
-@vtable2 = internal unnamed_addr constant { [2 x i32] } { [2 x i32] [
-  i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vfunc3_live_extern to i64), i64 ptrtoint (ptr @vtable2 to i64)) to i32),
-  i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vfunc4_dead_extern to i64), i64 ptrtoint (ptr @vtable2 to i64)) to i32)
-]}, align 4, !type !3, !type !4, !vcall_visibility !{i64 2}
-!3 = !{i64 0, !"vfunc3.type"}
-!4 = !{i64 4, !"vfunc4.type"}
-
-; CHECK:      @vtable2 = internal unnamed_addr constant { [2 x i32] } { [2 x i32] [
-; CHECK-SAME:   i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vfunc3_live_extern to i64), i64 ptrtoint (ptr @vtable2 to i64)) to i32),
-; CHECK-SAME:   i32 0
-; CHECK-SAME: ] }, align 4, !type !3, !type !4, !vcall_visibility !2
-
 ; (1) vfunc1_live is referenced from @main, stays alive
 define internal void @vfunc1_live() {
   ; CHECK: define internal void @vfunc1_live(
@@ -43,19 +29,9 @@ define internal void @vfunc2_dead() {
   ret void
 }
 
-; (3) vfunc3_live_extern is referenced from @main, stays alive
-; CHECK: declare void @vfunc3_live_extern
-declare void @vfunc3_live_extern()
-
-; (4) vfunc4_dead_extern is never referenced, gets removed and vtable slot is null'd
-; CHECK-NOT: declare void @vfunc4_dead_extern
-declare void @vfunc4_dead_extern()
-
 define void @main() {
   %1 = ptrtoint ptr @vtable to i64 ; to keep @vtable alive
   %2 = tail call { ptr, i1 } @llvm.type.checked.load(ptr null, i32 0, metadata !"vfunc1.type")
-  %3 = ptrtoint ptr @vtable2 to i64 ; to keep @vtable2 alive
-  %4 = tail call { ptr, i1 } @llvm.type.checked.load(ptr null, i32 0, metadata !"vfunc3.type")
   ret void
 }