[llvm-branch-commits] [clang] 16ab081 - [clang][fat-lto-objects] Make module flags match non-FatLTO pipelines (#83159)
Tom Stellard via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Mon Mar 11 12:49:05 PDT 2024
Author: Paul Kirth
Date: 2024-03-11T12:47:52-07:00
New Revision: 16ab0812d2010dad76f87d4d50da8e79e0e75e71
URL: https://github.com/llvm/llvm-project/commit/16ab0812d2010dad76f87d4d50da8e79e0e75e71
DIFF: https://github.com/llvm/llvm-project/commit/16ab0812d2010dad76f87d4d50da8e79e0e75e71.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.
(cherry picked from commit 7d8b50aaab8e0f935e3cb1f3f397e98b9e3ee241)
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 7877e20d77f772..4f22d35f9d3a94 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,
@@ -1029,7 +1037,8 @@ 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",
@@ -1040,11 +1049,9 @@ 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));
}
@@ -1058,24 +1065,17 @@ 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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