[llvm] [LLVM] Maintain element type of @llvm.compiler.used/@llvm.used if it already exists (PR #162660)
via llvm-commits
llvm-commits at lists.llvm.org
Thu Oct 9 07:05:29 PDT 2025
Juan Manuel Martinez =?utf-8?q?Caamaño?= <juamarti at amd.com>,
Juan Manuel Martinez =?utf-8?q?Caamaño?= <juamarti at amd.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/162660 at github.com>
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Juan Manuel Martinez Caamaño (jmmartinez)
<details>
<summary>Changes</summary>
At the moment, the address space for the pointer stored in the `llvm.compiler.used/llvm.used` is not well defined:
1. Clang uses the language default address space,
2. LLVM helpers from `ModuleUtils` use the 0 address space,
3. and BitcodeWriter (for fembed-bitcode) tries to preserve the element type if it already exists, 0 otherwise.
This PR doesn't solve this issue. It only adds one test that documents one problem with it, and makes the BitcodeWriter use the llvm helpers to reduce the places where these variables change.
Without this patch, the test added in the PR fails with an assertion:
```
UtilsTests: /home/juamarti/llvm/_llvm/llvm/lib/IR/Constants.cpp:1327:
static Constant *llvm::ConstantArray::getImpl(ArrayType *, ArrayRef<Constant *>):
Assertion `C->getType() == Ty->getElementType() && "Wrong type in array element initializer"' failed.
```
---
Full diff: https://github.com/llvm/llvm-project/pull/162660.diff
4 Files Affected:
- (modified) llvm/lib/Bitcode/Writer/BitcodeWriter.cpp (+30-40)
- (modified) llvm/lib/Bitcode/Writer/CMakeLists.txt (+1)
- (modified) llvm/lib/Transforms/Utils/ModuleUtils.cpp (+2-1)
- (modified) llvm/unittests/Transforms/Utils/ModuleUtilsTest.cpp (+17)
``````````diff
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 7ed140d392fca..f7afa393f3e00 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -75,6 +75,7 @@
#include "llvm/Support/SHA1.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
@@ -5850,25 +5851,25 @@ static const char *getSectionNameForCommandline(const Triple &T) {
void llvm::embedBitcodeInModule(llvm::Module &M, llvm::MemoryBufferRef Buf,
bool EmbedBitcode, bool EmbedCmdline,
const std::vector<uint8_t> &CmdArgs) {
- // Save llvm.compiler.used and remove it.
- SmallVector<Constant *, 2> UsedArray;
- SmallVector<GlobalValue *, 4> UsedGlobals;
- GlobalVariable *Used = collectUsedGlobalVariables(M, UsedGlobals, true);
- Type *UsedElementType = Used ? Used->getValueType()->getArrayElementType()
- : PointerType::getUnqual(M.getContext());
- for (auto *GV : UsedGlobals) {
- if (GV->getName() != "llvm.embedded.module" &&
- GV->getName() != "llvm.cmdline")
- UsedArray.push_back(
- ConstantExpr::getPointerBitCastOrAddrSpaceCast(GV, UsedElementType));
- }
- if (Used)
- Used->eraseFromParent();
// Embed the bitcode for the llvm module.
std::string Data;
ArrayRef<uint8_t> ModuleData;
Triple T(M.getTargetTriple());
+ SmallVector<GlobalValue *, 2> NewGlobals;
+
+ auto IsCmdOrBitcode = [&](Constant *C) {
+ GlobalVariable *GV = dyn_cast<GlobalVariable>(C);
+ StringRef Name = GV ? GV->getName() : "";
+ if (EmbedBitcode && Name == "llvm.embedded.module")
+ return true;
+ if (EmbedCmdline && Name == "llvm.cmdline")
+ return true;
+ return false;
+ };
+
+ if (EmbedBitcode || EmbedCmdline)
+ removeFromUsedLists(M, IsCmdOrBitcode);
if (EmbedBitcode) {
if (Buf.getBufferSize() == 0 ||
@@ -5887,23 +5888,22 @@ void llvm::embedBitcodeInModule(llvm::Module &M, llvm::MemoryBufferRef Buf,
}
llvm::Constant *ModuleConstant =
llvm::ConstantDataArray::get(M.getContext(), ModuleData);
- llvm::GlobalVariable *GV = new llvm::GlobalVariable(
+ llvm::GlobalVariable *EmbeddedModule = new llvm::GlobalVariable(
M, ModuleConstant->getType(), true, llvm::GlobalValue::PrivateLinkage,
ModuleConstant);
- GV->setSection(getSectionNameForBitcode(T));
+ EmbeddedModule->setSection(getSectionNameForBitcode(T));
// Set alignment to 1 to prevent padding between two contributions from input
// sections after linking.
- GV->setAlignment(Align(1));
- UsedArray.push_back(
- ConstantExpr::getPointerBitCastOrAddrSpaceCast(GV, UsedElementType));
+ EmbeddedModule->setAlignment(Align(1));
+ NewGlobals.push_back(EmbeddedModule);
if (llvm::GlobalVariable *Old =
M.getGlobalVariable("llvm.embedded.module", true)) {
assert(Old->hasZeroLiveUses() &&
"llvm.embedded.module can only be used once in llvm.compiler.used");
- GV->takeName(Old);
+ EmbeddedModule->takeName(Old);
Old->eraseFromParent();
} else {
- GV->setName("llvm.embedded.module");
+ EmbeddedModule->setName("llvm.embedded.module");
}
// Skip if only bitcode needs to be embedded.
@@ -5913,30 +5913,20 @@ void llvm::embedBitcodeInModule(llvm::Module &M, llvm::MemoryBufferRef Buf,
CmdArgs.size());
llvm::Constant *CmdConstant =
llvm::ConstantDataArray::get(M.getContext(), CmdData);
- GV = new llvm::GlobalVariable(M, CmdConstant->getType(), true,
- llvm::GlobalValue::PrivateLinkage,
- CmdConstant);
- GV->setSection(getSectionNameForCommandline(T));
- GV->setAlignment(Align(1));
- UsedArray.push_back(
- ConstantExpr::getPointerBitCastOrAddrSpaceCast(GV, UsedElementType));
+ GlobalVariable *CmdLine = new llvm::GlobalVariable(
+ M, CmdConstant->getType(), true, llvm::GlobalValue::PrivateLinkage,
+ CmdConstant);
+ CmdLine->setSection(getSectionNameForCommandline(T));
+ CmdLine->setAlignment(Align(1));
if (llvm::GlobalVariable *Old = M.getGlobalVariable("llvm.cmdline", true)) {
assert(Old->hasZeroLiveUses() &&
"llvm.cmdline can only be used once in llvm.compiler.used");
- GV->takeName(Old);
+ CmdLine->takeName(Old);
Old->eraseFromParent();
} else {
- GV->setName("llvm.cmdline");
+ CmdLine->setName("llvm.cmdline");
}
+ NewGlobals.push_back(CmdLine);
+ appendToCompilerUsed(M, NewGlobals);
}
-
- if (UsedArray.empty())
- return;
-
- // Recreate llvm.compiler.used.
- ArrayType *ATy = ArrayType::get(UsedElementType, UsedArray.size());
- auto *NewUsed = new GlobalVariable(
- M, ATy, false, llvm::GlobalValue::AppendingLinkage,
- llvm::ConstantArray::get(ATy, UsedArray), "llvm.compiler.used");
- NewUsed->setSection("llvm.metadata");
}
diff --git a/llvm/lib/Bitcode/Writer/CMakeLists.txt b/llvm/lib/Bitcode/Writer/CMakeLists.txt
index 2c508ca9fae95..5bbb872a90341 100644
--- a/llvm/lib/Bitcode/Writer/CMakeLists.txt
+++ b/llvm/lib/Bitcode/Writer/CMakeLists.txt
@@ -15,4 +15,5 @@ add_llvm_component_library(LLVMBitWriter
ProfileData
Support
TargetParser
+ TransformUtils
)
diff --git a/llvm/lib/Transforms/Utils/ModuleUtils.cpp b/llvm/lib/Transforms/Utils/ModuleUtils.cpp
index 596849ecab742..d1acb0ff1ad6b 100644
--- a/llvm/lib/Transforms/Utils/ModuleUtils.cpp
+++ b/llvm/lib/Transforms/Utils/ModuleUtils.cpp
@@ -138,10 +138,11 @@ static void appendToUsedList(Module &M, StringRef Name, ArrayRef<GlobalValue *>
SmallSetVector<Constant *, 16> Init;
collectUsedGlobals(GV, Init);
+ Type *ArrayEltTy = GV ? GV->getValueType()->getArrayElementType()
+ : PointerType::getUnqual(M.getContext());
if (GV)
GV->eraseFromParent();
- Type *ArrayEltTy = llvm::PointerType::getUnqual(M.getContext());
for (auto *V : Values)
Init.insert(ConstantExpr::getPointerBitCastOrAddrSpaceCast(V, ArrayEltTy));
diff --git a/llvm/unittests/Transforms/Utils/ModuleUtilsTest.cpp b/llvm/unittests/Transforms/Utils/ModuleUtilsTest.cpp
index d4094c5307060..0cc408af43bc5 100644
--- a/llvm/unittests/Transforms/Utils/ModuleUtilsTest.cpp
+++ b/llvm/unittests/Transforms/Utils/ModuleUtilsTest.cpp
@@ -69,6 +69,23 @@ TEST(ModuleUtils, AppendToUsedList2) {
EXPECT_EQ(1, getListSize(*M, "llvm.used"));
}
+TEST(ModuleUtils, AppendToUsedList3) {
+ LLVMContext C;
+
+ std::unique_ptr<Module> M = parseIR(C, R"(
+ @x = addrspace(1) global [2 x i32] zeroinitializer, align 4
+ @y = addrspace(2) global [2 x i32] zeroinitializer, align 4
+ @llvm.compiler.used = appending global [1 x ptr addrspace (3)] [ptr addrspace(3) addrspacecast (ptr addrspace (1) @x to ptr addrspace(3))]
+ )");
+ GlobalVariable *X = M->getNamedGlobal("x");
+ GlobalVariable *Y = M->getNamedGlobal("y");
+ EXPECT_EQ(1, getListSize(*M, "llvm.compiler.used"));
+ appendToCompilerUsed(*M, X);
+ EXPECT_EQ(1, getListSize(*M, "llvm.compiler.used"));
+ appendToCompilerUsed(*M, Y);
+ EXPECT_EQ(2, getListSize(*M, "llvm.compiler.used"));
+}
+
using AppendFnType = decltype(&appendToGlobalCtors);
using TransformFnType = decltype(&transformGlobalCtors);
using ParamType = std::tuple<StringRef, AppendFnType, TransformFnType>;
``````````
</details>
https://github.com/llvm/llvm-project/pull/162660
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