[clang] [clang][fat-lto-objects] Make module flags match non-FatLTO pipelines (PR #83159)
Paul Kirth via cfe-commits
cfe-commits at lists.llvm.org
Tue Feb 27 09:44:12 PST 2024
https://github.com/ilovepi created https://github.com/llvm/llvm-project/pull/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.
>From 0a37b8e52fe5e17fff3f6e88bf25f1969bbe8bb4 Mon Sep 17 00:00:00 2001
From: Paul Kirth <paulkirth at google.com>
Date: Tue, 27 Feb 2024 17:43:58 +0000
Subject: [PATCH] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20initia?=
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Created using spr 1.3.4
---
clang/lib/CodeGen/BackendUtil.cpp | 29 +++++++++++++---------------
clang/test/CodeGen/fat-lto-objects.c | 21 +++++++++++++++++++-
2 files changed, 33 insertions(+), 17 deletions(-)
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index a310825240237c..7b409e8c9a17ca 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -186,6 +186,11 @@ class EmitAssemblyHelper {
TargetTriple.getVendor() != llvm::Triple::Apple;
}
+ bool shouldEmitUnifiedLTOModueFlag() const {
+ return CodeGenOpts.UnifiedLTO &&
+ (CodeGenOpts.PrepareForThinLTO || shouldEmitRegularLTOSummary());
+ }
+
public:
EmitAssemblyHelper(DiagnosticsEngine &_Diags,
const HeaderSearchOptions &HeaderSearchOpts,
@@ -1036,7 +1041,8 @@ 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 +1053,9 @@ 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 +1069,17 @@ 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 different 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..459a6e4ecb8758 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 -flto=full -fsplit-lto-unit -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 -Xclang -triple -Xclang x86_64-unknown-linux-gnu -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 -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 -Xclang -triple -Xclang x86_64-unknown-linux-gnu -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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