https://github.com/stuij created
https://github.com/llvm/llvm-project/pull/117140
because:
- This brings Clang in line with GCC for which this is the default for ARM
- It frees up a register, so performance increase, especially on Thumb/6-M
- It will decrease code size
>From 4a85a0cd98bf328f31465d47c56640abdf7ec08c Mon Sep 17 00:00:00 2001
From: Ties Stuij <ties.st...@arm.com>
Date: Fri, 15 Nov 2024 13:19:08 +0000
Subject: [PATCH] [clang][ARM] disable frame pointers by default for bare metal
ARM targets
because:
- This brings Clang in line with GCC for which this is the default for ARM
- It frees up a register, so performance increase, especially on Thumb/6-M
- It will also decrease code size
---
clang/lib/Driver/ToolChains/BareMetal.cpp | 8 +++++-
clang/lib/Driver/ToolChains/BareMetal.h | 2 ++
clang/lib/Driver/ToolChains/CommonArgs.cpp | 5 ++++
clang/test/Driver/frame-pointer-elim.c | 29 ++++++++++++++++++++++
4 files changed, 43 insertions(+), 1 deletion(-)
diff --git a/clang/lib/Driver/ToolChains/BareMetal.cpp
b/clang/lib/Driver/ToolChains/BareMetal.cpp
index f9a73f60973e4c..13b510e7e70994 100644
--- a/clang/lib/Driver/ToolChains/BareMetal.cpp
+++ b/clang/lib/Driver/ToolChains/BareMetal.cpp
@@ -128,8 +128,11 @@ BareMetal::BareMetal(const Driver &D, const llvm::Triple
&Triple,
}
}
+namespace clang {
+namespace driver {
+namespace toolchains {
/// Is the triple {arm,armeb,thumb,thumbeb}-none-none-{eabi,eabihf} ?
-static bool isARMBareMetal(const llvm::Triple &Triple) {
+bool isARMBareMetal(const llvm::Triple &Triple) {
if (Triple.getArch() != llvm::Triple::arm &&
Triple.getArch() != llvm::Triple::thumb &&
Triple.getArch() != llvm::Triple::armeb &&
@@ -148,6 +151,9 @@ static bool isARMBareMetal(const llvm::Triple &Triple) {
return true;
}
+} // namespace clang
+} // namespace driver
+} // namespace clang
/// Is the triple {aarch64.aarch64_be}-none-elf?
static bool isAArch64BareMetal(const llvm::Triple &Triple) {
diff --git a/clang/lib/Driver/ToolChains/BareMetal.h
b/clang/lib/Driver/ToolChains/BareMetal.h
index b385c8cf76aab0..ae09bcedd78a28 100644
--- a/clang/lib/Driver/ToolChains/BareMetal.h
+++ b/clang/lib/Driver/ToolChains/BareMetal.h
@@ -19,6 +19,8 @@ namespace driver {
namespace toolchains {
+bool isARMBareMetal(const llvm::Triple &Triple);
+
class LLVM_LIBRARY_VISIBILITY BareMetal : public ToolChain {
public:
BareMetal(const Driver &D, const llvm::Triple &Triple,
diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp
b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 8d977149e62485..8d54d0a8649cc9 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -19,6 +19,7 @@
#include "Arch/SystemZ.h"
#include "Arch/VE.h"
#include "Arch/X86.h"
+#include "BareMetal.h"
#include "HIPAMD.h"
#include "Hexagon.h"
#include "MSP430.h"
@@ -151,6 +152,10 @@ static bool useFramePointerForTargetByDefault(const
llvm::opt::ArgList &Args,
}
}
+ if (toolchains::isARMBareMetal(Triple)) {
+ return false;
+ }
+
return true;
}
diff --git a/clang/test/Driver/frame-pointer-elim.c
b/clang/test/Driver/frame-pointer-elim.c
index cdedcc7ae4c89f..667c47b34bc703 100644
--- a/clang/test/Driver/frame-pointer-elim.c
+++ b/clang/test/Driver/frame-pointer-elim.c
@@ -162,5 +162,34 @@
// RUN: FileCheck --check-prefix=KEEP-NON-LEAF %s
// RUN: not %clang -### --target=riscv64-linux-android -mbig-endian -O1 -S %s
2>&1 | \
// RUN: FileCheck --check-prefix=KEEP-NON-LEAF %s
+
+// On ARM backend bare metal targets, frame pointer is omitted
+// RUN: %clang -### --target=arm-arm-none-eabi -S %s 2>&1 | \
+// RUN: FileCheck --check-prefix=KEEP-NONE %s
+// RUN: %clang -### --target=arm-arm-none-eabihf -S %s 2>&1 | \
+// RUN: FileCheck --check-prefix=KEEP-NONE %s
+// RUN: %clang -### --target=arm-arm-none-eabi -S -fno-omit-frame-pointer %s
2>&1 | \
+// RUN: FileCheck --check-prefix=KEEP-ALL %s
+// RUN: %clang -### --target=arm-arm-none-eabihf -S -fno-omit-frame-pointer %s
2>&1 | \
+// RUN: FileCheck --check-prefix=KEEP-ALL %s
+// RUN: %clang -### --target=arm-arm-none-eabi -S -O1 %s 2>&1 | \
+// RUN: FileCheck --check-prefix=KEEP-NONE %s
+// RUN: %clang -### --target=arm-arm-none-eabihf -S -O1 %s 2>&1 | \
+// RUN: FileCheck --check-prefix=KEEP-NONE %s
+// RUN: %clang -### --target=arm-arm-none-eabi -S -O1 -fno-omit-frame-pointer
%s 2>&1 | \
+// RUN: FileCheck --check-prefix=KEEP-ALL %s
+// RUN: %clang -### --target=arm-arm-none-eabihf -S -O1
-fno-omit-frame-pointer %s 2>&1 | \
+// RUN: FileCheck --check-prefix=KEEP-ALL %s
+
+// AArch64 bare metal targets behave like hosted targets
+// RUN: %clang -### --target=aarch64-none-elf -S %s 2>&1 | \
+// RUN: FileCheck --check-prefix=KEEP-NON-LEAF %s
+// RUN: %clang -### --target=aarch64-none-elf -S -O1 %s 2>&1 | \
+// RUN: FileCheck --check-prefix=KEEP-NON-LEAF %s
+// RUN: %clang -### --target=aarch64-none-elf -S -fno-omit-frame-pointer %s
2>&1 | \
+// RUN: FileCheck --check-prefix=KEEP-NON-LEAF %s
+// RUN: %clang -### --target=aarch64-none-elf -S -O1 -fno-omit-frame-pointer
%s 2>&1 | \
+// RUN: FileCheck --check-prefix=KEEP-NON-LEAF %s
+
void f0() {}
void f1() { f0(); }
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