Driver, CodeGen: Handle -falign-functions, -fno-align-functions and -falign-functions=1 correctly. #149445
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@llvm/pr-subscribers-clang-driver @llvm/pr-subscribers-clang-codegen Author: Peter Collingbourne (pcc) ChangesFull diff: https://github.com/llvm/llvm-project/pull/149445.diff 6 Files Affected:
diff --git a/clang/include/clang/Driver/CommonArgs.h b/clang/include/clang/Driver/CommonArgs.h
index 49c7149380fba..42590fbd89e9a 100644
--- a/clang/include/clang/Driver/CommonArgs.h
+++ b/clang/include/clang/Driver/CommonArgs.h
@@ -85,8 +85,8 @@ const char *RelocationModelName(llvm::Reloc::Model Model);
std::tuple<llvm::Reloc::Model, unsigned, bool>
ParsePICArgs(const ToolChain &ToolChain, const llvm::opt::ArgList &Args);
-unsigned ParseFunctionAlignment(const ToolChain &TC,
- const llvm::opt::ArgList &Args);
+llvm::MaybeAlign ParseFunctionAlignment(const ToolChain &TC,
+ const llvm::opt::ArgList &Args);
void addDebugInfoKind(llvm::opt::ArgStringList &CmdArgs,
llvm::codegenoptions::DebugInfoKind DebugInfoKind);
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 236cc3d9e8907..905f0c70750a1 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -2760,9 +2760,11 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
if (alignment)
F->setAlignment(llvm::Align(alignment));
- if (!D->hasAttr<AlignedAttr>())
- if (LangOpts.FunctionAlignment)
- F->setAlignment(llvm::Align(1ull << LangOpts.FunctionAlignment));
+ if (!D->hasAttr<AlignedAttr>()) {
+ llvm::MaybeAlign Align = llvm::decodeMaybeAlign(LangOpts.FunctionAlignment);
+ if (Align)
+ F->setAlignment(*Align);
+ }
// Some C++ ABIs require 2-byte alignment for member functions, in order to
// reserve a bit for differentiating between virtual and non-virtual member
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 8880c9375143f..5a3cbed6839e8 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -40,6 +40,7 @@
#include "llvm/Frontend/Debug/Options.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Option/ArgList.h"
+#include "llvm/Support/Alignment.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Compression.h"
@@ -5516,12 +5517,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
CheckCodeGenerationOptions(D, Args);
- unsigned FunctionAlignment = ParseFunctionAlignment(TC, Args);
- assert(FunctionAlignment <= 31 && "function alignment will be truncated!");
- if (FunctionAlignment) {
- CmdArgs.push_back("-function-alignment");
- CmdArgs.push_back(Args.MakeArgString(std::to_string(FunctionAlignment)));
- }
+ llvm::MaybeAlign FunctionAlignment = ParseFunctionAlignment(TC, Args);
+ CmdArgs.push_back("-function-alignment");
+ CmdArgs.push_back(
+ Args.MakeArgString(std::to_string(llvm::encode(FunctionAlignment))));
// We support -falign-loops=N where N is a power of 2. GCC supports more
// forms.
diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 651a39c03bb54..672b154d1855f 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -2120,29 +2120,33 @@ tools::ParsePICArgs(const ToolChain &ToolChain, const ArgList &Args) {
// [0, 65536]. If the value is not a power-of-two, it will be rounded up to
// the nearest power-of-two.
//
-// If we return `0`, the frontend will default to the backend's preferred
-// alignment.
+// If we return `MaybeAlign()`, the frontend will default to the backend's
+// preferred alignment.
//
// NOTE: icc only allows values between [0, 4096]. icc uses `-falign-functions`
// to mean `-falign-functions=16`. GCC defaults to the backend's preferred
// alignment. For unaligned functions, we default to the backend's preferred
// alignment.
-unsigned tools::ParseFunctionAlignment(const ToolChain &TC,
- const ArgList &Args) {
+llvm::MaybeAlign tools::ParseFunctionAlignment(const ToolChain &TC,
+ const ArgList &Args) {
const Arg *A = Args.getLastArg(options::OPT_falign_functions,
options::OPT_falign_functions_EQ,
options::OPT_fno_align_functions);
- if (!A || A->getOption().matches(options::OPT_fno_align_functions))
- return 0;
+ if (!A)
+ return llvm::MaybeAlign();
+
+ if (A->getOption().matches(options::OPT_fno_align_functions))
+ return llvm::Align(1);
if (A->getOption().matches(options::OPT_falign_functions))
- return 0;
+ return llvm::MaybeAlign();
unsigned Value = 0;
if (StringRef(A->getValue()).getAsInteger(10, Value) || Value > 65536)
TC.getDriver().Diag(diag::err_drv_invalid_int_value)
<< A->getAsString(Args) << A->getValue();
- return Value ? llvm::Log2_32_Ceil(std::min(Value, 65536u)) : Value;
+ return Value ? llvm::Align(1 << llvm::Log2_32_Ceil(std::min(Value, 65536u)))
+ : llvm::MaybeAlign();
}
void tools::addDebugInfoKind(
diff --git a/clang/test/CodeGen/function-alignment.c b/clang/test/CodeGen/function-alignment.c
index 8564ceb02354b..c3e06e1c571d5 100644
--- a/clang/test/CodeGen/function-alignment.c
+++ b/clang/test/CodeGen/function-alignment.c
@@ -1,6 +1,7 @@
-// RUN: %clang_cc1 -emit-llvm %s -o - | FileCheck %s -check-prefix CHECK-NONE
-// RUN: %clang_cc1 -emit-llvm -function-alignment 4 %s -o - | FileCheck %s -check-prefix CHECK-16
-// RUN: %clang_cc1 -emit-llvm -function-alignment 5 %s -o - | FileCheck %s -check-prefix CHECK-32
+// RUN: %clang_cc1 -emit-llvm -function-alignment 0 %s -o - | FileCheck %s -check-prefix CHECK-NONE
+// RUN: %clang_cc1 -emit-llvm -function-alignment 1 %s -o - | FileCheck %s -check-prefix CHECK-1
+// RUN: %clang_cc1 -emit-llvm -function-alignment 5 %s -o - | FileCheck %s -check-prefix CHECK-16
+// RUN: %clang_cc1 -emit-llvm -function-alignment 6 %s -o - | FileCheck %s -check-prefix CHECK-32
void f(void) {}
void __attribute__((__aligned__(64))) g(void) {}
@@ -8,6 +9,9 @@ void __attribute__((__aligned__(64))) g(void) {}
// CHECK-NONE-NOT: define {{(dso_local )?}}void @f() #0 align
// CHECK-NONE: define {{(dso_local )?}}void @g() #0 align 64
+// CHECK-1: define {{(dso_local )?}}void @f() #0 align 1
+// CHECK-1: define {{(dso_local )?}}void @g() #0 align 64
+
// CHECK-16: define {{(dso_local )?}}void @f() #0 align 16
// CHECK-16: define {{(dso_local )?}}void @g() #0 align 64
diff --git a/clang/test/Driver/function-alignment.c b/clang/test/Driver/function-alignment.c
index ed4cc80f7ed4f..751c695512cf6 100644
--- a/clang/test/Driver/function-alignment.c
+++ b/clang/test/Driver/function-alignment.c
@@ -1,17 +1,17 @@
// RUN: %clang -### %s 2>&1 | FileCheck %s -check-prefix CHECK-0
-// RUN: %clang -### -falign-functions %s 2>&1 | FileCheck %s -check-prefix CHECK-1
+// RUN: %clang -### -falign-functions %s 2>&1 | FileCheck %s -check-prefix CHECK-0
+// RUN: %clang -### -fno-align-functions %s 2>&1 | FileCheck %s -check-prefix CHECK-1
// RUN: %clang -### -falign-functions=1 %s 2>&1 | FileCheck %s -check-prefix CHECK-1
// RUN: %clang -### -falign-functions=2 %s 2>&1 | FileCheck %s -check-prefix CHECK-2
// RUN: %clang -### -falign-functions=3 %s 2>&1 | FileCheck %s -check-prefix CHECK-3
-// RUN: %clang -### -falign-functions=4 %s 2>&1 | FileCheck %s -check-prefix CHECK-4
+// RUN: %clang -### -falign-functions=4 %s 2>&1 | FileCheck %s -check-prefix CHECK-3
// RUN: not %clang -### -falign-functions=65537 %s 2>&1 | FileCheck %s -check-prefix CHECK-ERR-65537
// RUN: not %clang -### -falign-functions=a %s 2>&1 | FileCheck %s -check-prefix CHECK-ERR-A
-// CHECK-0-NOT: "-function-alignment"
-// CHECK-1-NOT: "-function-alignment"
-// CHECK-2: "-function-alignment" "1"
-// CHECK-3: "-function-alignment" "2"
-// CHECK-4: "-function-alignment" "2"
+// CHECK-0: "-function-alignment" "0"
+// CHECK-1: "-function-alignment" "1"
+// CHECK-2: "-function-alignment" "2"
+// CHECK-3: "-function-alignment" "3"
// CHECK-ERR-65537: error: invalid integral value '65537' in '-falign-functions=65537'
// CHECK-ERR-A: error: invalid integral value 'a' in '-falign-functions=a'
|
|
@llvm/pr-subscribers-clang Author: Peter Collingbourne (pcc) ChangesFull diff: https://github.com/llvm/llvm-project/pull/149445.diff 6 Files Affected:
diff --git a/clang/include/clang/Driver/CommonArgs.h b/clang/include/clang/Driver/CommonArgs.h
index 49c7149380fba..42590fbd89e9a 100644
--- a/clang/include/clang/Driver/CommonArgs.h
+++ b/clang/include/clang/Driver/CommonArgs.h
@@ -85,8 +85,8 @@ const char *RelocationModelName(llvm::Reloc::Model Model);
std::tuple<llvm::Reloc::Model, unsigned, bool>
ParsePICArgs(const ToolChain &ToolChain, const llvm::opt::ArgList &Args);
-unsigned ParseFunctionAlignment(const ToolChain &TC,
- const llvm::opt::ArgList &Args);
+llvm::MaybeAlign ParseFunctionAlignment(const ToolChain &TC,
+ const llvm::opt::ArgList &Args);
void addDebugInfoKind(llvm::opt::ArgStringList &CmdArgs,
llvm::codegenoptions::DebugInfoKind DebugInfoKind);
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 236cc3d9e8907..905f0c70750a1 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -2760,9 +2760,11 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
if (alignment)
F->setAlignment(llvm::Align(alignment));
- if (!D->hasAttr<AlignedAttr>())
- if (LangOpts.FunctionAlignment)
- F->setAlignment(llvm::Align(1ull << LangOpts.FunctionAlignment));
+ if (!D->hasAttr<AlignedAttr>()) {
+ llvm::MaybeAlign Align = llvm::decodeMaybeAlign(LangOpts.FunctionAlignment);
+ if (Align)
+ F->setAlignment(*Align);
+ }
// Some C++ ABIs require 2-byte alignment for member functions, in order to
// reserve a bit for differentiating between virtual and non-virtual member
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 8880c9375143f..5a3cbed6839e8 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -40,6 +40,7 @@
#include "llvm/Frontend/Debug/Options.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Option/ArgList.h"
+#include "llvm/Support/Alignment.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Compression.h"
@@ -5516,12 +5517,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
CheckCodeGenerationOptions(D, Args);
- unsigned FunctionAlignment = ParseFunctionAlignment(TC, Args);
- assert(FunctionAlignment <= 31 && "function alignment will be truncated!");
- if (FunctionAlignment) {
- CmdArgs.push_back("-function-alignment");
- CmdArgs.push_back(Args.MakeArgString(std::to_string(FunctionAlignment)));
- }
+ llvm::MaybeAlign FunctionAlignment = ParseFunctionAlignment(TC, Args);
+ CmdArgs.push_back("-function-alignment");
+ CmdArgs.push_back(
+ Args.MakeArgString(std::to_string(llvm::encode(FunctionAlignment))));
// We support -falign-loops=N where N is a power of 2. GCC supports more
// forms.
diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 651a39c03bb54..672b154d1855f 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -2120,29 +2120,33 @@ tools::ParsePICArgs(const ToolChain &ToolChain, const ArgList &Args) {
// [0, 65536]. If the value is not a power-of-two, it will be rounded up to
// the nearest power-of-two.
//
-// If we return `0`, the frontend will default to the backend's preferred
-// alignment.
+// If we return `MaybeAlign()`, the frontend will default to the backend's
+// preferred alignment.
//
// NOTE: icc only allows values between [0, 4096]. icc uses `-falign-functions`
// to mean `-falign-functions=16`. GCC defaults to the backend's preferred
// alignment. For unaligned functions, we default to the backend's preferred
// alignment.
-unsigned tools::ParseFunctionAlignment(const ToolChain &TC,
- const ArgList &Args) {
+llvm::MaybeAlign tools::ParseFunctionAlignment(const ToolChain &TC,
+ const ArgList &Args) {
const Arg *A = Args.getLastArg(options::OPT_falign_functions,
options::OPT_falign_functions_EQ,
options::OPT_fno_align_functions);
- if (!A || A->getOption().matches(options::OPT_fno_align_functions))
- return 0;
+ if (!A)
+ return llvm::MaybeAlign();
+
+ if (A->getOption().matches(options::OPT_fno_align_functions))
+ return llvm::Align(1);
if (A->getOption().matches(options::OPT_falign_functions))
- return 0;
+ return llvm::MaybeAlign();
unsigned Value = 0;
if (StringRef(A->getValue()).getAsInteger(10, Value) || Value > 65536)
TC.getDriver().Diag(diag::err_drv_invalid_int_value)
<< A->getAsString(Args) << A->getValue();
- return Value ? llvm::Log2_32_Ceil(std::min(Value, 65536u)) : Value;
+ return Value ? llvm::Align(1 << llvm::Log2_32_Ceil(std::min(Value, 65536u)))
+ : llvm::MaybeAlign();
}
void tools::addDebugInfoKind(
diff --git a/clang/test/CodeGen/function-alignment.c b/clang/test/CodeGen/function-alignment.c
index 8564ceb02354b..c3e06e1c571d5 100644
--- a/clang/test/CodeGen/function-alignment.c
+++ b/clang/test/CodeGen/function-alignment.c
@@ -1,6 +1,7 @@
-// RUN: %clang_cc1 -emit-llvm %s -o - | FileCheck %s -check-prefix CHECK-NONE
-// RUN: %clang_cc1 -emit-llvm -function-alignment 4 %s -o - | FileCheck %s -check-prefix CHECK-16
-// RUN: %clang_cc1 -emit-llvm -function-alignment 5 %s -o - | FileCheck %s -check-prefix CHECK-32
+// RUN: %clang_cc1 -emit-llvm -function-alignment 0 %s -o - | FileCheck %s -check-prefix CHECK-NONE
+// RUN: %clang_cc1 -emit-llvm -function-alignment 1 %s -o - | FileCheck %s -check-prefix CHECK-1
+// RUN: %clang_cc1 -emit-llvm -function-alignment 5 %s -o - | FileCheck %s -check-prefix CHECK-16
+// RUN: %clang_cc1 -emit-llvm -function-alignment 6 %s -o - | FileCheck %s -check-prefix CHECK-32
void f(void) {}
void __attribute__((__aligned__(64))) g(void) {}
@@ -8,6 +9,9 @@ void __attribute__((__aligned__(64))) g(void) {}
// CHECK-NONE-NOT: define {{(dso_local )?}}void @f() #0 align
// CHECK-NONE: define {{(dso_local )?}}void @g() #0 align 64
+// CHECK-1: define {{(dso_local )?}}void @f() #0 align 1
+// CHECK-1: define {{(dso_local )?}}void @g() #0 align 64
+
// CHECK-16: define {{(dso_local )?}}void @f() #0 align 16
// CHECK-16: define {{(dso_local )?}}void @g() #0 align 64
diff --git a/clang/test/Driver/function-alignment.c b/clang/test/Driver/function-alignment.c
index ed4cc80f7ed4f..751c695512cf6 100644
--- a/clang/test/Driver/function-alignment.c
+++ b/clang/test/Driver/function-alignment.c
@@ -1,17 +1,17 @@
// RUN: %clang -### %s 2>&1 | FileCheck %s -check-prefix CHECK-0
-// RUN: %clang -### -falign-functions %s 2>&1 | FileCheck %s -check-prefix CHECK-1
+// RUN: %clang -### -falign-functions %s 2>&1 | FileCheck %s -check-prefix CHECK-0
+// RUN: %clang -### -fno-align-functions %s 2>&1 | FileCheck %s -check-prefix CHECK-1
// RUN: %clang -### -falign-functions=1 %s 2>&1 | FileCheck %s -check-prefix CHECK-1
// RUN: %clang -### -falign-functions=2 %s 2>&1 | FileCheck %s -check-prefix CHECK-2
// RUN: %clang -### -falign-functions=3 %s 2>&1 | FileCheck %s -check-prefix CHECK-3
-// RUN: %clang -### -falign-functions=4 %s 2>&1 | FileCheck %s -check-prefix CHECK-4
+// RUN: %clang -### -falign-functions=4 %s 2>&1 | FileCheck %s -check-prefix CHECK-3
// RUN: not %clang -### -falign-functions=65537 %s 2>&1 | FileCheck %s -check-prefix CHECK-ERR-65537
// RUN: not %clang -### -falign-functions=a %s 2>&1 | FileCheck %s -check-prefix CHECK-ERR-A
-// CHECK-0-NOT: "-function-alignment"
-// CHECK-1-NOT: "-function-alignment"
-// CHECK-2: "-function-alignment" "1"
-// CHECK-3: "-function-alignment" "2"
-// CHECK-4: "-function-alignment" "2"
+// CHECK-0: "-function-alignment" "0"
+// CHECK-1: "-function-alignment" "1"
+// CHECK-2: "-function-alignment" "2"
+// CHECK-3: "-function-alignment" "3"
// CHECK-ERR-65537: error: invalid integral value '65537' in '-falign-functions=65537'
// CHECK-ERR-A: error: invalid integral value 'a' in '-falign-functions=a'
|
arsenm
reviewed
Jul 18, 2025
Comment on lines
+5521
to
+5523
| CmdArgs.push_back("-function-alignment"); | ||
| CmdArgs.push_back( | ||
| Args.MakeArgString(std::to_string(llvm::encode(FunctionAlignment)))); |
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Why add the arg in the !FunctionAlignment case?
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I guess it isn't strictly necessary, but it ensures that CodeGen will always receive a value that was encoded by llvm::encode. That being said it seems unlikely that we will actually change the meaning of the 0 encoding.
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I'd just omit it and reduce flag spam
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