[clang] 7d8b50a - [clang][fat-lto-objects] Make module flags match non-FatLTO pipelines (#83159)
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Wed Feb 28 19:11:59 PST 2024
Author: Paul Kirth
Date: 2024-02-28T19:11:55-08:00
New Revision: 7d8b50aaab8e0f935e3cb1f3f397e98b9e3ee241
URL: https://github.com/llvm/llvm-project/commit/7d8b50aaab8e0f935e3cb1f3f397e98b9e3ee241
DIFF: https://github.com/llvm/llvm-project/commit/7d8b50aaab8e0f935e3cb1f3f397e98b9e3ee241.diff
LOG: [clang][fat-lto-objects] Make module flags match non-FatLTO pipelines (#83159)
In addition to being rather hard to follow, there isn't a good reason
why FatLTO shouldn't just share the same code for setting module flags
for (Thin)LTO. This patch simplifies the logic and makes sure we use set
these flags in a consistent way, independent of FatLTO.
Additionally, we now test that output in the .llvm.lto section actually
matches the output from Full and Thin LTO compilation.
Added:
Modified:
clang/lib/CodeGen/BackendUtil.cpp
clang/test/CodeGen/fat-lto-objects.c
Removed:
################################################################################
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index a310825240237c..056f790d41853d 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -186,6 +186,14 @@ class EmitAssemblyHelper {
TargetTriple.getVendor() != llvm::Triple::Apple;
}
+ /// Check whether we should emit a flag for UnifiedLTO.
+ /// The UnifiedLTO module flag should be set when UnifiedLTO is enabled for
+ /// ThinLTO or Full LTO with module summaries.
+ bool shouldEmitUnifiedLTOModueFlag() const {
+ return CodeGenOpts.UnifiedLTO &&
+ (CodeGenOpts.PrepareForThinLTO || shouldEmitRegularLTOSummary());
+ }
+
public:
EmitAssemblyHelper(DiagnosticsEngine &_Diags,
const HeaderSearchOptions &HeaderSearchOpts,
@@ -1036,7 +1044,8 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
if (!actionRequiresCodeGen(Action) && CodeGenOpts.VerifyModule)
MPM.addPass(VerifierPass());
- if (Action == Backend_EmitBC || Action == Backend_EmitLL) {
+ if (Action == Backend_EmitBC || Action == Backend_EmitLL ||
+ CodeGenOpts.FatLTO) {
if (CodeGenOpts.PrepareForThinLTO && !CodeGenOpts.DisableLLVMPasses) {
if (!TheModule->getModuleFlag("EnableSplitLTOUnit"))
TheModule->addModuleFlag(llvm::Module::Error, "EnableSplitLTOUnit",
@@ -1047,11 +1056,9 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
if (!ThinLinkOS)
return;
}
- if (CodeGenOpts.UnifiedLTO)
- TheModule->addModuleFlag(llvm::Module::Error, "UnifiedLTO", uint32_t(1));
MPM.addPass(ThinLTOBitcodeWriterPass(
*OS, ThinLinkOS ? &ThinLinkOS->os() : nullptr));
- } else {
+ } else if (Action == Backend_EmitLL) {
MPM.addPass(PrintModulePass(*OS, "", CodeGenOpts.EmitLLVMUseLists,
/*EmitLTOSummary=*/true));
}
@@ -1065,24 +1072,17 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
if (!TheModule->getModuleFlag("EnableSplitLTOUnit"))
TheModule->addModuleFlag(llvm::Module::Error, "EnableSplitLTOUnit",
uint32_t(1));
- if (CodeGenOpts.UnifiedLTO)
- TheModule->addModuleFlag(llvm::Module::Error, "UnifiedLTO", uint32_t(1));
}
- if (Action == Backend_EmitBC)
+ if (Action == Backend_EmitBC) {
MPM.addPass(BitcodeWriterPass(*OS, CodeGenOpts.EmitLLVMUseLists,
EmitLTOSummary));
- else
+ } else if (Action == Backend_EmitLL) {
MPM.addPass(PrintModulePass(*OS, "", CodeGenOpts.EmitLLVMUseLists,
EmitLTOSummary));
+ }
}
- }
- if (CodeGenOpts.FatLTO) {
- // Set the EnableSplitLTOUnit and UnifiedLTO module flags, since FatLTO
- // uses a
diff erent action than Backend_EmitBC or Backend_EmitLL.
- if (!TheModule->getModuleFlag("EnableSplitLTOUnit"))
- TheModule->addModuleFlag(llvm::Module::Error, "EnableSplitLTOUnit",
- uint32_t(CodeGenOpts.EnableSplitLTOUnit));
- if (CodeGenOpts.UnifiedLTO && !TheModule->getModuleFlag("UnifiedLTO"))
+
+ if (shouldEmitUnifiedLTOModueFlag())
TheModule->addModuleFlag(llvm::Module::Error, "UnifiedLTO", uint32_t(1));
}
diff --git a/clang/test/CodeGen/fat-lto-objects.c b/clang/test/CodeGen/fat-lto-objects.c
index afce798c5c8194..b50567c024fc8c 100644
--- a/clang/test/CodeGen/fat-lto-objects.c
+++ b/clang/test/CodeGen/fat-lto-objects.c
@@ -11,10 +11,11 @@
// RUN: llvm-objcopy --dump-section=.llvm.lto=%t.full.split.bc %t.full.split.o
// RUN: llvm-dis %t.full.split.bc -o - | FileCheck %s --check-prefixes=FULL,SPLIT,NOUNIFIED
+/// Full LTO always sets EnableSplitLTOUnit when the summary is used.
// RUN: %clang -cc1 -triple x86_64-unknown-linux-gnu -flto=full -ffat-lto-objects -emit-obj < %s -o %t.full.nosplit.o
// RUN: llvm-readelf -S %t.full.nosplit.o | FileCheck %s --check-prefixes=ELF
// RUN: llvm-objcopy --dump-section=.llvm.lto=%t.full.nosplit.bc %t.full.nosplit.o
-// RUN: llvm-dis %t.full.nosplit.bc -o - | FileCheck %s --check-prefixes=FULL,NOSPLIT,NOUNIFIED
+// RUN: llvm-dis %t.full.nosplit.bc -o - | FileCheck %s --check-prefixes=FULL,SPLIT,NOUNIFIED
// RUN: %clang -cc1 -triple x86_64-unknown-linux-gnu -flto=thin -fsplit-lto-unit -ffat-lto-objects -emit-obj < %s -o %t.thin.split.o
// RUN: llvm-readelf -S %t.thin.split.o | FileCheck %s --check-prefixes=ELF
@@ -34,6 +35,21 @@
// RUN: %clang -cc1 -triple x86_64-unknown-linux-gnu -flto=full -ffat-lto-objects -fsplit-lto-unit -S < %s -o - \
// RUN: | FileCheck %s --check-prefixes=ASM
+/// Make sure that FatLTO generates .llvm.lto sections that are the same as the output from normal LTO compilations
+// RUN: %clang -O2 --target=x86_64-unknown-linux-gnu -fPIE -flto=full -ffat-lto-objects -c %s -o %t.fatlto.full.o
+// RUN: llvm-objcopy --dump-section=.llvm.lto=%t.fatlto.full.bc %t.fatlto.full.o
+// RUN: llvm-dis < %t.fatlto.full.bc -o %t.fatlto.full.ll
+// RUN: %clang -O2 --target=x86_64-unknown-linux-gnu -fPIE -flto=full -c %s -o %t.nofat.full.bc
+// RUN: llvm-dis < %t.nofat.full.bc -o %t.nofat.full.ll
+// RUN:
diff %t.fatlto.full.ll %t.nofat.full.ll
+
+// RUN: %clang -O2 --target=x86_64-unknown-linux-gnu -fPIE -flto=thin -ffat-lto-objects -c %s -o %t.fatlto.thin.o
+// RUN: llvm-objcopy --dump-section=.llvm.lto=%t.fatlto.thin.bc %t.fatlto.thin.o
+// RUN: llvm-dis < %t.fatlto.thin.bc -o %t.fatlto.thin.ll
+// RUN: %clang -O2 --target=x86_64-unknown-linux-gnu -fPIE -flto=thin -c %s -o %t.nofat.thin.bc
+// RUN: llvm-dis < %t.nofat.thin.bc -o %t.nofat.thin.ll
+// RUN:
diff %t.fatlto.thin.ll %t.nofat.thin.ll
+
/// Be sure we enable split LTO units correctly under -ffat-lto-objects.
// SPLIT: ![[#]] = !{i32 1, !"EnableSplitLTOUnit", i32 1}
// NOSPLIT: ![[#]] = !{i32 1, !"EnableSplitLTOUnit", i32 0}
@@ -51,6 +67,9 @@
// ASM-NEXT: .asciz "BC
// ASM-NEXT: .size .Lllvm.embedded.object
+const char* foo = "foo";
+
int test(void) {
+ const char* bar = "bar";
return 0xabcd;
}
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