Hello cfe-commits,
The attached patch is for clang to use -fomit-frame-pointer by default
for all PowerPC targets when optimizing code. Right now, clang uses
-fomit-frame-pointer for PowerPC Linux and NetBSD but not for other
targets. I have been running `clang -target powerpc-openbsd`.
The patch is for llvm-project.git master. I previously posted this
patch to https://bugs.llvm.org/show_bug.cgi?id=41094 , but the patch
in this email is for a newer revision of master.
In most functions, the frame pointer in r31 is an unnecessary extra
copy of the stack pointer in r1. GCC is using -fomit-frame-pointer by
default (in my PowerPC machine running OpenBSD/macppc); I want Clang
to be at least as good as GCC. Also, this patch helps me to compare
the output of `clang -target powerpc-openbsd -O2 -S` with the output
for Linux or NetBSD. In bug 41094, I showed how -fomit-frame-pointer
simplifies the C function `void nothing(void) {}`.
This is my first mail to cfe-commits; I'm using the instructions at
http://llvm.org/docs/DeveloperPolicy.html#making-and-submitting-a-patch
--
George Koehler <kern...@gmail.com>
From a7906214c4751b4c181546ae48ecd05c8f84f07b Mon Sep 17 00:00:00 2001
From: George Koehler <kern...@gmail.com>
Date: Tue, 2 Apr 2019 11:29:19 -0400
Subject: [PATCH] Use -fomit-frame-pointer when optimizing PowerPC code
This enables -fomit-frame-pointer when optimizing code for all PowerPC
targets, instead of only Linux and NetBSD.
---
clang/lib/Driver/ToolChains/Clang.cpp | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp
b/clang/lib/Driver/ToolChains/Clang.cpp
index a5b98aad54d..6bfca0a5f15 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -523,8 +523,12 @@ static bool useFramePointerForTargetByDefault(const
ArgList &Args,
// XCore never wants frame pointers, regardless of OS.
// WebAssembly never wants frame pointers.
return false;
+ case llvm::Triple::ppc:
+ case llvm::Triple::ppc64:
+ case llvm::Triple::ppc64le:
case llvm::Triple::riscv32:
case llvm::Triple::riscv64:
+ // PowerPC's frame pointer is often an extra copy of the stack pointer.
return !areOptimizationsEnabled(Args);
default:
break;
@@ -542,9 +546,6 @@ static bool useFramePointerForTargetByDefault(const ArgList
&Args,
case llvm::Triple::mips64el:
case llvm::Triple::mips:
case llvm::Triple::mipsel:
- case llvm::Triple::ppc:
- case llvm::Triple::ppc64:
- case llvm::Triple::ppc64le:
case llvm::Triple::systemz:
case llvm::Triple::x86:
case llvm::Triple::x86_64:
--
2.19.1
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