[clang] [LTO] A static relocation model can override the PIC level wrt treating external address as directly accessible (PR #65512)
Wolfgang Pieb via cfe-commits
cfe-commits at lists.llvm.org
Wed Sep 6 11:28:15 PDT 2023
https://github.com/wolfy1961 created https://github.com/llvm/llvm-project/pull/65512:
As described in issue [#64999](https://github.com/llvm/llvm-project/issues/64999), commit [e018cbf7208](https://github.com/llvm/llvm-project/commit/e018cbf7208b3d34f18997ddee84c66cee32fb1b) caused the symbol __stack_chk_guard to not become dso_local when PIC is enabled in a module. However, during LTO we can force a static relocation model, which overrides the PIC level. In this case __stack_chk_guard should become dso_local.
For this purpose we're adding a boolean to the interface of getDirectAccessExternalData() to indicate the relocation model.
Fixes https://github.com/llvm/llvm-project/issues/64999
>From 6a176368c90183fc1744b73632746636fe46da42 Mon Sep 17 00:00:00 2001
From: wpieb <Wolfgang.Pieb at sony.com>
Date: Tue, 5 Sep 2023 10:43:23 -0700
Subject: [PATCH] [LTO] A static relocation model can override the PIC level
wrt treating external address as directly accessible.
Fixes https://github.com/llvm/llvm-project/issues/64999
---
clang/lib/CodeGen/CodeGenModule.cpp | 5 +--
llvm/include/llvm/IR/Module.h | 2 +-
llvm/lib/CodeGen/TargetLoweringBase.cpp | 3 +-
llvm/lib/IR/Module.cpp | 4 +--
llvm/lib/Target/X86/X86ISelLoweringCall.cpp | 3 +-
llvm/test/LTO/ARM/ssp-static-reloc.ll | 38 +++++++++++++++++++++
6 files changed, 48 insertions(+), 7 deletions(-)
create mode 100644 llvm/test/LTO/ARM/ssp-static-reloc.ll
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 95f185f5824d8c..f0a10f5d294270 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1127,7 +1127,8 @@ void CodeGenModule::Release() {
if (LangOpts.HLSL)
getHLSLRuntime().finishCodeGen();
- if (uint32_t PLevel = Context.getLangOpts().PICLevel) {
+ uint32_t PLevel = Context.getLangOpts().PICLevel;
+ if (PLevel) {
assert(PLevel < 3 && "Invalid PIC Level");
getModule().setPICLevel(static_cast<llvm::PICLevel::Level>(PLevel));
if (Context.getLangOpts().PIE)
@@ -1152,7 +1153,7 @@ void CodeGenModule::Release() {
getModule().setRtLibUseGOT();
if (getTriple().isOSBinFormatELF() &&
CodeGenOpts.DirectAccessExternalData !=
- getModule().getDirectAccessExternalData()) {
+ getModule().getDirectAccessExternalData(PLevel == 0)) {
getModule().setDirectAccessExternalData(
CodeGenOpts.DirectAccessExternalData);
}
diff --git a/llvm/include/llvm/IR/Module.h b/llvm/include/llvm/IR/Module.h
index 670a40b28eabbe..bf2c41bb9c3e44 100644
--- a/llvm/include/llvm/IR/Module.h
+++ b/llvm/include/llvm/IR/Module.h
@@ -947,7 +947,7 @@ class LLVM_EXTERNAL_VISIBILITY Module {
/// Get/set whether referencing global variables can use direct access
/// relocations on ELF targets.
- bool getDirectAccessExternalData() const;
+ bool getDirectAccessExternalData(bool IsStaticRelocModel) const;
void setDirectAccessExternalData(bool Value);
/// Get/set whether synthesized functions should get the uwtable attribute.
diff --git a/llvm/lib/CodeGen/TargetLoweringBase.cpp b/llvm/lib/CodeGen/TargetLoweringBase.cpp
index 3e4bff5ddce126..e1f439fd32dad1 100644
--- a/llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -2016,7 +2016,8 @@ void TargetLoweringBase::insertSSPDeclarations(Module &M) const {
"__stack_chk_guard");
// FreeBSD has "__stack_chk_guard" defined externally on libc.so
- if (M.getDirectAccessExternalData() &&
+ if (M.getDirectAccessExternalData(TM.getRelocationModel() ==
+ Reloc::Static) &&
!TM.getTargetTriple().isWindowsGNUEnvironment() &&
!TM.getTargetTriple().isOSFreeBSD() &&
!TM.getTargetTriple().isOSDarwin())
diff --git a/llvm/lib/IR/Module.cpp b/llvm/lib/IR/Module.cpp
index 73354a8f36d215..8186f256007c48 100644
--- a/llvm/lib/IR/Module.cpp
+++ b/llvm/lib/IR/Module.cpp
@@ -672,12 +672,12 @@ void Module::setRtLibUseGOT() {
addModuleFlag(ModFlagBehavior::Max, "RtLibUseGOT", 1);
}
-bool Module::getDirectAccessExternalData() const {
+bool Module::getDirectAccessExternalData(bool IsStaticRelocModel) const {
auto *Val = cast_or_null<ConstantAsMetadata>(
getModuleFlag("direct-access-external-data"));
if (Val)
return cast<ConstantInt>(Val->getValue())->getZExtValue() > 0;
- return getPICLevel() == PICLevel::NotPIC;
+ return getPICLevel() == PICLevel::NotPIC || IsStaticRelocModel;
}
void Module::setDirectAccessExternalData(bool Value) {
diff --git a/llvm/lib/Target/X86/X86ISelLoweringCall.cpp b/llvm/lib/Target/X86/X86ISelLoweringCall.cpp
index 754d2042105e57..9eeb9bf682b1f4 100644
--- a/llvm/lib/Target/X86/X86ISelLoweringCall.cpp
+++ b/llvm/lib/Target/X86/X86ISelLoweringCall.cpp
@@ -606,7 +606,8 @@ Value *X86TargetLowering::getIRStackGuard(IRBuilderBase &IRB) const {
nullptr, GuardSymb, nullptr,
GlobalValue::NotThreadLocal, AddressSpace);
if (!Subtarget.isTargetDarwin())
- GV->setDSOLocal(M->getDirectAccessExternalData());
+ GV->setDSOLocal(M->getDirectAccessExternalData(
+ getTargetMachine().getRelocationModel() == Reloc::Static));
}
return GV;
}
diff --git a/llvm/test/LTO/ARM/ssp-static-reloc.ll b/llvm/test/LTO/ARM/ssp-static-reloc.ll
new file mode 100644
index 00000000000000..3c8688d8e7b1c6
--- /dev/null
+++ b/llvm/test/LTO/ARM/ssp-static-reloc.ll
@@ -0,0 +1,38 @@
+; Check that we do not generate an extra indirection accessing the stack guard
+; variable, when the relocation model is static.
+;
+; RUN: llvm-as < %s > %t.bc
+; RUN: llvm-lto -O0 -relocation-model=static -o %t.o %t.bc
+; RUN: llvm-objdump -d -r %t.o | FileCheck %s
+
+target triple = "armv4t-unknown-unknown"
+
+define arm_aapcscc i8 @foo() #0 {
+entry:
+ %arr = alloca [200 x i8], align 1
+ call void @llvm.memset.p0.i32(ptr align 1 %arr, i8 0, i32 200, i1 false)
+ %arrayidx = getelementptr inbounds [200 x i8], ptr %arr, i32 0, i8 5
+ %0 = load i8, ptr %arrayidx, align 1
+ ret i8 %0
+}
+
+; CHECK: <foo>:
+; CHECK: [[#%x,CURPC:]]:{{.*}} ldr r[[REG1:[0-9]+]], [pc, #0x[[#%x,OFFSET:]]]
+; CHECK-NEXT: ldr r[[REG2:[0-9]+]], [r[[REG1]]]
+; CHECK-NEXT: str r[[REG2]],
+; CHECK: [[#CURPC + OFFSET + 8]]:{{.*}}.word
+; CHECK-NEXT: R_ARM_ABS32 __stack_chk_guard
+
+declare void @llvm.memset.p0.i32(ptr nocapture writeonly, i8, i32, i1 immarg)
+
+define arm_aapcscc i32 @main() {
+entry:
+ %call = call arm_aapcscc i8 @foo()
+ %conv = zext i8 %call to i32
+ ret i32 %conv
+}
+
+attributes #0 = { noinline nounwind optnone sspstrong }
+
+!llvm.module.flags = !{!0}
+!0 = !{i32 8, !"PIC Level", i32 2}
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