[llvm] 86dbcaf - [llvm] Teach GlobalDCE about dso_local_equivalent
Leonard Chan via llvm-commits
llvm-commits at lists.llvm.org
Thu Feb 23 15:14:15 PST 2023
Author: Leonard Chan
Date: 2023-02-23T23:13:57Z
New Revision: 86dbcafd0cdc88ae85896c6f12ecaa6006aeba54
URL: https://github.com/llvm/llvm-project/commit/86dbcafd0cdc88ae85896c6f12ecaa6006aeba54
DIFF: https://github.com/llvm/llvm-project/commit/86dbcafd0cdc88ae85896c6f12ecaa6006aeba54.diff
LOG: [llvm] Teach GlobalDCE about dso_local_equivalent
This way, C++ relative-vtables can also participate in GlobalDCE. This
depends on some TypeMetadataUtils.cpp bits in D134320, but that
dependency can be removed and included here if necessary.
Differential Revision: https://reviews.llvm.org/D135928
Added:
Modified:
llvm/include/llvm/Analysis/TypeMetadataUtils.h
llvm/lib/Analysis/TypeMetadataUtils.cpp
llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers-bad.ll
llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers-gep.ll
llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/Analysis/TypeMetadataUtils.h b/llvm/include/llvm/Analysis/TypeMetadataUtils.h
index 571bbc2741804..6e4101c0c8052 100644
--- a/llvm/include/llvm/Analysis/TypeMetadataUtils.h
+++ b/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 `F`, and replaces the entire pattern with a constant zero.
-void replaceRelativePointerUsersWithZero(Function *F);
+/// target is `C`, and replaces the entire pattern with a constant zero.
+void replaceRelativePointerUsersWithZero(Constant *C);
} // namespace llvm
diff --git a/llvm/lib/Analysis/TypeMetadataUtils.cpp b/llvm/lib/Analysis/TypeMetadataUtils.cpp
index 53f7a9277e4ca..ad300cb245094 100644
--- a/llvm/lib/Analysis/TypeMetadataUtils.cpp
+++ b/llvm/lib/Analysis/TypeMetadataUtils.cpp
@@ -213,19 +213,26 @@ Constant *llvm::getPointerAtOffset(Constant *I, uint64_t Offset, Module &M,
return nullptr;
}
-void llvm::replaceRelativePointerUsersWithZero(Function *F) {
- for (auto *U : F->users()) {
- auto *PtrExpr = dyn_cast<ConstantExpr>(U);
- if (!PtrExpr || PtrExpr->getOpcode() != Instruction::PtrToInt)
- continue;
+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)
- continue;
+ for (auto *PtrToIntUser : PtrExpr->users()) {
+ auto *SubExpr = dyn_cast<ConstantExpr>(PtrToIntUser);
+ if (!SubExpr || SubExpr->getOpcode() != Instruction::Sub)
+ return;
- SubExpr->replaceNonMetadataUsesWith(
- ConstantInt::get(SubExpr->getType(), 0));
- }
+ SubExpr->replaceNonMetadataUsesWith(
+ ConstantInt::get(SubExpr->getType(), 0));
+ }
+}
+
+void llvm::replaceRelativePointerUsersWithZero(Constant *C) {
+ for (auto *U : C->users()) {
+ if (auto *Equiv = dyn_cast<DSOLocalEquivalent>(U))
+ replaceRelativePointerUsersWithZero(Equiv);
+ else
+ replaceRelativePointerUserWithZero(U);
}
}
diff --git a/llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers-bad.ll b/llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers-bad.ll
index 9d87fdb084a12..9a4bff80383cb 100644
--- a/llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers-bad.ll
+++ b/llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers-bad.ll
@@ -16,14 +16,32 @@ 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
+ at 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
}
diff --git a/llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers-gep.ll b/llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers-gep.ll
index fb45d37dde6e4..d89b024e7a6d0 100644
--- a/llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers-gep.ll
+++ b/llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers-gep.ll
@@ -19,6 +19,20 @@ 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
+ at 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(
@@ -31,9 +45,19 @@ 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
}
diff --git a/llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers.ll b/llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers.ll
index 76a617ea99e6f..b652765296bc5 100644
--- a/llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers.ll
+++ b/llvm/test/Transforms/GlobalDCE/virtual-functions-relative-pointers.ll
@@ -17,6 +17,20 @@ 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.
+ at 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(
@@ -29,9 +43,19 @@ 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
}
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