[clang] [llvm] [MTE] generalize overalignment / size of MTE globals (PR #121957)
Florian Mayer via llvm-commits
llvm-commits at lists.llvm.org
Fri Feb 21 17:07:54 PST 2025
https://github.com/fmayer updated https://github.com/llvm/llvm-project/pull/121957
>From 2feb85c15f64546cb6874e1ca0a1310bd1e1bedd Mon Sep 17 00:00:00 2001
From: Florian Mayer <fmayer at google.com>
Date: Tue, 7 Jan 2025 07:57:09 -0800
Subject: [PATCH 1/2] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20in?=
=?UTF-8?q?itial=20version?=
MIME-Version: 1.0
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Content-Transfer-Encoding: 8bit
Created using spr 1.3.4
---
llvm/include/llvm/IR/GlobalVariable.h | 7 +++++
llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp | 34 ++++++++++++++--------
llvm/lib/IR/Globals.cpp | 10 +++++++
3 files changed, 39 insertions(+), 12 deletions(-)
diff --git a/llvm/include/llvm/IR/GlobalVariable.h b/llvm/include/llvm/IR/GlobalVariable.h
index 83e484816d7d4..c1f8cdc4fd0a6 100644
--- a/llvm/include/llvm/IR/GlobalVariable.h
+++ b/llvm/include/llvm/IR/GlobalVariable.h
@@ -267,6 +267,13 @@ class GlobalVariable : public GlobalObject, public ilist_node<GlobalVariable> {
getAttributes().hasAttribute("rodata-section");
}
+ MaybeAlign getRequiredGlobalAlignment() {
+ return isTagged() && getAlign().valueOrOne() < 16 ? MaybeAlign(16)
+ : std::nullopt;
+ }
+
+ std::optional<uint64_t> getRequiredGlobalSize();
+
/// Get the custom code model raw value of this global.
///
unsigned getCodeModelRaw() const {
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 7bd3fb33b47d2..8e594a8f92b20 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -2398,17 +2398,23 @@ void AsmPrinter::emitRemarksSection(remarks::RemarkStreamer &RS) {
OutStreamer->emitBinaryData(Buf);
}
-static void tagGlobalDefinition(Module &M, GlobalVariable *G) {
- Constant *Initializer = G->getInitializer();
+static uint64_t globalSize(const GlobalVariable &G) {
+ const Constant *Initializer = G.getInitializer();
uint64_t SizeInBytes =
- M.getDataLayout().getTypeAllocSize(Initializer->getType());
+ G.getParent()->getDataLayout().getTypeAllocSize(Initializer->getType());
- uint64_t NewSize = alignTo(SizeInBytes, 16);
- if (SizeInBytes != NewSize) {
+ return SizeInBytes;
+}
+
+static void tagGlobalDefinition(GlobalVariable *G) {
+ Module &M = *G->getParent();
+ uint64_t SizeInBytes = globalSize(*G);
+ if (auto NewSize = G->getRequiredGlobalSize()) {
+ assert(*NewSize > SizeInBytes);
// Pad the initializer out to the next multiple of 16 bytes.
- llvm::SmallVector<uint8_t> Init(NewSize - SizeInBytes, 0);
+ llvm::SmallVector<uint8_t> Init(*NewSize - SizeInBytes, 0);
Constant *Padding = ConstantDataArray::get(M.getContext(), Init);
- Initializer = ConstantStruct::getAnon({Initializer, Padding});
+ auto *Initializer = ConstantStruct::getAnon({G->getInitializer(), Padding});
auto *NewGV = new GlobalVariable(
M, Initializer->getType(), G->isConstant(), G->getLinkage(),
Initializer, "", G, G->getThreadLocalMode(), G->getAddressSpace());
@@ -2422,8 +2428,10 @@ static void tagGlobalDefinition(Module &M, GlobalVariable *G) {
G = NewGV;
}
- if (G->getAlign().valueOrOne() < 16)
- G->setAlignment(Align(16));
+ if (auto Align = G->getRequiredGlobalAlignment()) {
+ assert(*Align > G->getAlign().valueOrOne());
+ G->setAlignment(*Align);
+ }
// Ensure that tagged globals don't get merged by ICF - as they should have
// different tags at runtime.
@@ -2438,12 +2446,14 @@ bool AsmPrinter::doFinalization(Module &M) {
std::vector<GlobalVariable *> GlobalsToTag;
for (GlobalVariable &G : M.globals()) {
- if (G.isDeclaration() || !G.isTagged())
+ if (G.isDeclaration())
continue;
- GlobalsToTag.push_back(&G);
+ if (G.getRequiredGlobalAlignment().has_value() ||
+ G.getRequiredGlobalSize().has_value())
+ GlobalsToTag.push_back(&G);
}
for (GlobalVariable *G : GlobalsToTag)
- tagGlobalDefinition(M, G);
+ tagGlobalDefinition(G);
// Gather all GOT equivalent globals in the module. We really need two
// passes over the globals: one to compute and another to avoid its emission
diff --git a/llvm/lib/IR/Globals.cpp b/llvm/lib/IR/Globals.cpp
index db5e1cb57b1ba..79ff120c250e4 100644
--- a/llvm/lib/IR/Globals.cpp
+++ b/llvm/lib/IR/Globals.cpp
@@ -540,6 +540,16 @@ void GlobalVariable::setCodeModel(CodeModel::Model CM) {
assert(getCodeModel() == CM && "Code model representation error!");
}
+std::optional<uint64_t> GlobalVariable::getRequiredGlobalSize() {
+ if (!isTagged())
+ return std::nullopt;
+ Constant *Initializer = getInitializer();
+ uint64_t SizeInBytes =
+ getParent()->getDataLayout().getTypeAllocSize(Initializer->getType());
+ uint64_t Aligned = alignTo(SizeInBytes, 16);
+ return Aligned != SizeInBytes ? std::optional(Aligned) : std::nullopt;
+}
+
//===----------------------------------------------------------------------===//
// GlobalAlias Implementation
//===----------------------------------------------------------------------===//
>From 64e954bafd4ecd7c9c3d968e5438f0780a1d4546 Mon Sep 17 00:00:00 2001
From: Florian Mayer <fmayer at google.com>
Date: Fri, 21 Feb 2025 17:07:36 -0800
Subject: [PATCH 2/2] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20ch?=
=?UTF-8?q?anges=20introduced=20through=20rebase?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Created using spr 1.3.4
[skip ci]
---
clang/test/CodeGen/memtag-globals-asm.cpp | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/clang/test/CodeGen/memtag-globals-asm.cpp b/clang/test/CodeGen/memtag-globals-asm.cpp
index 186045f8f2fb5..254624ec0b7bb 100644
--- a/clang/test/CodeGen/memtag-globals-asm.cpp
+++ b/clang/test/CodeGen/memtag-globals-asm.cpp
@@ -51,6 +51,7 @@
// CHECK-A: .memtag global_int
// CHECK-A: .globl global_int
// CHECK-A: .p2align 4, 0x0
+// CHECK-A: .zero 16
// CHECK-A: .size global_int, 16
int global_int;
// CHECK-B: .memtag _ZL9local_int
@@ -66,6 +67,7 @@ static char local_buffer[16];
// CHECK-D: .p2align 4, 0x0
// CHECK-D: _ZL22local_buffer_local_end:
// CHECK-D: .xword _ZL12local_buffer+16
+// CHECK-D: .zero 8
// CHECK-D: .size _ZL22local_buffer_local_end, 16
static char* local_buffer_local_end = &local_buffer[16];
// CHECK-E: .memtag local_buffer_global_end
@@ -73,6 +75,7 @@ static char* local_buffer_local_end = &local_buffer[16];
// CHECK-E .p2align 4, 0x0
// CHECK-E: local_buffer_global_end:
// CHECK-E: .xword _ZL12local_buffer+16
+// CHECK-E: .zero 8
// CHECK-E: .size local_buffer_global_end, 16
char* local_buffer_global_end = &local_buffer[16];
@@ -85,6 +88,7 @@ char global_buffer[16];
// CHECK-G: .p2align 4, 0x0
// CHECK-G: _ZL23global_buffer_local_end:
// CHECK-G: .xword global_buffer+16
+// CHECK-G: .zero 8
// CHECK-G: .size _ZL23global_buffer_local_end, 16
static char* global_buffer_local_end = &global_buffer[16];
// CHECK-H: .memtag global_buffer_global_end
@@ -104,6 +108,7 @@ class MyClass {
// CHECK-I: .memtag _ZN7MyClass12my_class_intE
// CHECK-I: .globl _ZN7MyClass12my_class_intE
// CHECK-I: .p2align 4, 0x0
+// CHECK-I: .zero 16
// CHECK-I: .size _ZN7MyClass12my_class_intE, 16
int MyClass::my_class_int;
// CHECK-NOT: .memtag _ZN7MyClass18my_class_const_intE
@@ -112,10 +117,12 @@ const int MyClass::my_class_const_int = 1;
// CHECK-J: .memtag global_my_class
// CHECK-J: .globl global_my_class
// CHECK-J: .p2align 4, 0x0
+// CHECK-J: .zero 8
// CHECK-J: .size global_my_class, 16
MyClass global_my_class;
// CHECK-K: .memtag _ZL14local_my_class
// CHECK-K: .p2align 4, 0x0
+// CHECK-K: .zero 8
// CHECK-K: .size _ZL14local_my_class, 16
static MyClass local_my_class;
@@ -123,12 +130,14 @@ static MyClass local_my_class;
static const char local_const_string[] = "this is a local string";
// CHECK-L: .memtag _ZL12local_string
// CHECK-L: .p2align 4, 0x0
+// CHECK-L: .zero 9
// CHECK-L: .size _ZL12local_string, 32
static char local_string[] = "this is a local string";
// CHECK-M: .memtag global_atomic_int
// CHECK-M: .globl global_atomic_int
// CHECK-M: .p2align 4, 0x0
+// CHECK-M: .zero 16
// CHECK-M: .size global_atomic_int, 16
_Atomic(int) global_atomic_int;
// CHECK-N: .memtag _ZL16local_atomic_int
@@ -144,6 +153,7 @@ union MyUnion {
// CHECK-O: .memtag global_union
// CHECK-O: .globl global_union
// CHECK-O: .p2align 4, 0x0
+// CHECK-O: .zero 16
// CHECK-O: .size global_union, 16
MyUnion global_union;
// CHECK-P: .memtag _ZL11local_union
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