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[LTO] A static relocation model can override the PIC level wrt treating external address as directly accessible #65512

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[LTO] A static relocation model can override the PIC level wrt treating external address as directly accessible #65512

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2e5abce
[LTO] A static relocation model can override the PIC level wrt treating
wolfy1961 Sep 5, 2023
2ddd45b
Adjust the test
wolfy1961 Sep 20, 2023
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5 changes: 3 additions & 2 deletions clang/lib/CodeGen/CodeGenModule.cpp
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Expand Up @@ -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)
Expand All @@ -1152,7 +1153,7 @@ void CodeGenModule::Release() {
getModule().setRtLibUseGOT();
if (getTriple().isOSBinFormatELF() &&
CodeGenOpts.DirectAccessExternalData !=
getModule().getDirectAccessExternalData()) {
getModule().getDirectAccessExternalData(PLevel == 0)) {
getModule().setDirectAccessExternalData(
CodeGenOpts.DirectAccessExternalData);
}
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2 changes: 1 addition & 1 deletion llvm/include/llvm/IR/Module.h
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Expand Up @@ -958,7 +958,7 @@ 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.
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3 changes: 2 additions & 1 deletion llvm/lib/CodeGen/TargetLoweringBase.cpp
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Expand Up @@ -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())
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4 changes: 2 additions & 2 deletions llvm/lib/IR/Module.cpp
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Expand Up @@ -687,12 +687,12 @@ 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) {
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3 changes: 2 additions & 1 deletion llvm/lib/Target/X86/X86ISelLoweringCall.cpp
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Expand Up @@ -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;
}
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8 changes: 3 additions & 5 deletions llvm/test/LTO/ARM/ssp-static-reloc.ll
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Expand Up @@ -2,9 +2,8 @@
; RUN: llvm-lto -O0 -relocation-model=static -o %t.o %t.bc
; RUN: llvm-objdump -d -r %t.o | FileCheck %s

; Confirm that we do generate one too many indirections accessing the stack guard
; variable, when the relocation model is static and the PIC level is not 0..
; This is preparation for the fix.
; Confirm that we do not generate one too many indirections accessing the stack guard
; variable, when the relocation model is static and the PIC level is not 0.
;
target triple = "armv4t-unknown-unknown"

Expand All @@ -20,8 +19,7 @@ entry:
; 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: ldr r[[REG3:[0-9]+]], [r[[REG2]]]
; CHECK-NEXT: str r[[REG3]],
; CHECK-NEXT: str r[[REG2]],
; CHECK: [[#CURPC + OFFSET + 8]]:{{.*}}.word
; CHECK-NEXT: R_ARM_ABS32 __stack_chk_guard

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