[clang] [clang-repl] Enable native CPU detection by default (PR #77491)
https://github.com/weliveindetail closed https://github.com/llvm/llvm-project/pull/77491 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang-repl] Enable native CPU detection by default (PR #77491)
weliveindetail wrote: Thanks for the quick review! https://github.com/llvm/llvm-project/pull/77491 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang-repl] Enable native CPU detection by default (PR #77491)
weliveindetail wrote: Oh and this matches the default behavior in Orc host detection btw: https://github.com/llvm/llvm-project/blob/release/17.x/llvm/lib/ExecutionEngine/Orc/JITTargetMachineBuilder.cpp#L35 https://github.com/llvm/llvm-project/pull/77491 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang-repl] Enable native CPU detection by default (PR #77491)
https://github.com/vgvassilev approved this pull request. Thank you for the patch, Stefan! Some of our downstream consumers use that flag for exactly these reasons. LGTM! https://github.com/llvm/llvm-project/pull/77491 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang-repl] Enable native CPU detection by default (PR #77491)
llvmbot wrote:
@llvm/pr-subscribers-clang
Author: Stefan Gränitz (weliveindetail)
Changes
We can pass `-mcpu=native` to the clang driver to let it consider the host CPU
when choosing the compile target for `clang-repl`. We can already achieve this
behavior with `clang-repl -Xcc -mcpu=native`, but it seems like a reasonable
default actually.
The trade-off between optimizing for a specific CPU and maximum compatibility
often leans towards the latter for static binaries, because distributing many
versions is cumbersome. However, when compiling at runtime, we know the exact
target CPU and we can use that to optimize the generated code.
This patch makes a difference especially for "scattered" architectures like
ARM. When cross-compiling for a Raspberry Pi for example, we may use a stock
toolchain like arm-linux-gnueabihf-gcc. The resulting binary will be compatible
with all hardware versions. This is handy, but they will all have
`arm-linux-gnueabihf` as their host triple. Previously, this caused the clang
driver to select triple `armv6kz-linux-gnueabihf` and CPU `arm1176jzf-s` as the
REPL target. After this patch the default triple and CPU on Raspberry Pi 4b
will be `armv8a-linux-gnueabihf` and `cortex-a72` respectively.
---
Full diff: https://github.com/llvm/llvm-project/pull/77491.diff
1 Files Affected:
- (modified) clang/lib/Interpreter/Interpreter.cpp (+1)
``diff
diff --git a/clang/lib/Interpreter/Interpreter.cpp
b/clang/lib/Interpreter/Interpreter.cpp
index c9fcef5b5b5af1..734fe90d0d89b4 100644
--- a/clang/lib/Interpreter/Interpreter.cpp
+++ b/clang/lib/Interpreter/Interpreter.cpp
@@ -148,6 +148,7 @@ IncrementalCompilerBuilder::create(std::vector ) {
// We do C++ by default; append right after argv[0] if no "-x" given
ClangArgv.insert(ClangArgv.end(), "-Xclang");
ClangArgv.insert(ClangArgv.end(), "-fincremental-extensions");
+ ClangArgv.insert(ClangArgv.end(), "-mcpu=native");
ClangArgv.insert(ClangArgv.end(), "-c");
// Put a dummy C++ file on to ensure there's at least one compile job for the
``
https://github.com/llvm/llvm-project/pull/77491
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[clang] [clang-repl] Enable native CPU detection by default (PR #77491)
https://github.com/weliveindetail created
https://github.com/llvm/llvm-project/pull/77491
We can pass `-mcpu=native` to the clang driver to let it consider the host CPU
when choosing the compile target for `clang-repl`. We can already achieve this
behavior with `clang-repl -Xcc -mcpu=native`, but it seems like a reasonable
default actually.
The trade-off between optimizing for a specific CPU and maximum compatibility
often leans towards the latter for static binaries, because distributing many
versions is cumbersome. However, when compiling at runtime, we know the exact
target CPU and we can use that to optimize the generated code.
This patch makes a difference especially for "scattered" architectures like
ARM. When cross-compiling for a Raspberry Pi for example, we may use a stock
toolchain like arm-linux-gnueabihf-gcc. The resulting binary will be compatible
with all hardware versions. This is handy, but they will all have
`arm-linux-gnueabihf` as their host triple. Previously, this caused the clang
driver to select triple `armv6kz-linux-gnueabihf` and CPU `arm1176jzf-s` as the
REPL target. After this patch the default triple and CPU on Raspberry Pi 4b
will be `armv8a-linux-gnueabihf` and `cortex-a72` respectively.
From 2a6847e9d1b2b91e7236208b3a62458a4fc7c78b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20Gr=C3=A4nitz?=
Date: Tue, 9 Jan 2024 14:52:29 +0100
Subject: [PATCH] [clang-repl] Enable native CPU detection by default
We can pass `-mcpu=native` to the clang driver to let it consider the host CPU
when choosing the compile target for `clang-repl`. We can already achieve this
behavior with `clang-repl -Xcc -mcpu=native`, but it seems like a reasonable
default actually.
The trade-off between optimizing for a specific CPU and maximum compatibility
often leans towards the latter for static binaries, because distributing many
versions is cumbersome. However, when compiling at runtime, we know the exact
target CPU and we can use that to optimize the generated code.
This patch makes a difference especially for "scattered" architectures like
ARM. When cross-compiling for a Raspberry Pi for example, we may use a stock
toolchain like arm-linux-gnueabihf-gcc. The resulting binary will be compatible
with all hardware versions. This is handy, but they will all have
`arm-linux-gnueabihf` as their host triple. Previously, this caused the clang
driver to select triple `armv6kz-linux-gnueabihf` and CPU `arm1176jzf-s` as the
REPL target. After this patch the default triple and CPU on Raspberry Pi 4b
will be `armv8a-linux-gnueabihf` and `cortex-a72` respectively.
---
clang/lib/Interpreter/Interpreter.cpp | 1 +
1 file changed, 1 insertion(+)
diff --git a/clang/lib/Interpreter/Interpreter.cpp
b/clang/lib/Interpreter/Interpreter.cpp
index c9fcef5b5b5af1..734fe90d0d89b4 100644
--- a/clang/lib/Interpreter/Interpreter.cpp
+++ b/clang/lib/Interpreter/Interpreter.cpp
@@ -148,6 +148,7 @@ IncrementalCompilerBuilder::create(std::vector ) {
// We do C++ by default; append right after argv[0] if no "-x" given
ClangArgv.insert(ClangArgv.end(), "-Xclang");
ClangArgv.insert(ClangArgv.end(), "-fincremental-extensions");
+ ClangArgv.insert(ClangArgv.end(), "-mcpu=native");
ClangArgv.insert(ClangArgv.end(), "-c");
// Put a dummy C++ file on to ensure there's at least one compile job for the
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