[libc-commits] [clang] [libc] [Clang] Make `--lto-partitions` only default for HIP (PR #133164)
Joseph Huber via libc-commits
libc-commits at lists.llvm.org
Wed Mar 26 14:07:38 PDT 2025
https://github.com/jhuber6 created https://github.com/llvm/llvm-project/pull/133164
Summary:
The default behavior for LTO on other targets does not specify the
number of LTO partitions. Recent changes made this default to 8 on
AMDGPU which had some issues with the `libc` project. The option to
disable this is HIP only so I think for now we should restrict this just
to HIP.
I'm definitely on board with getting some more parallelism here, but I
think it should probably be restricted to just offloading languages. The
new driver goes through the `--target=amdgcn-amd-amdhsa` for its output,
which means we'd need to forward the default somehow.
>From 8c8885d486ac72145d7fd7ba003db7ea9ab17a1f Mon Sep 17 00:00:00 2001
From: Joseph Huber <huberjn at outlook.com>
Date: Wed, 26 Mar 2025 16:03:20 -0500
Subject: [PATCH] [Clang] Make `--lto-partitions` only default for HIP
Summary:
The default behavior for LTO on other targets does not specify the
number of LTO partitions. Recent changes made this default to 8 on
AMDGPU which had some issues with the `libc` project. The option to
disable this is HIP only so I think for now we should restrict this just
to HIP.
I'm definitely on board with getting some more parallelism here, but I
think it should probably be restricted to just offloading languages. The
new driver goes through the `--target=amdgcn-amd-amdhsa` for its output,
which means we'd need to forward the default somehow.
---
clang/lib/Driver/ToolChains/AMDGPU.cpp | 22 ++++++++--------------
clang/test/Driver/amdgpu-toolchain.c | 16 +---------------
libc/startup/gpu/CMakeLists.txt | 10 ++--------
3 files changed, 11 insertions(+), 37 deletions(-)
diff --git a/clang/lib/Driver/ToolChains/AMDGPU.cpp b/clang/lib/Driver/ToolChains/AMDGPU.cpp
index e919f4e941f47..c754cae2f96b2 100644
--- a/clang/lib/Driver/ToolChains/AMDGPU.cpp
+++ b/clang/lib/Driver/ToolChains/AMDGPU.cpp
@@ -625,6 +625,7 @@ void amdgpu::Linker::ConstructJob(Compilation &C, const JobAction &JA,
CmdArgs.push_back("-shared");
}
+ llvm::errs() << JA.getOffloadingDeviceKind() << "\n";
addLinkerCompressDebugSectionsOption(getToolChain(), Args, CmdArgs);
Args.AddAllArgs(CmdArgs, options::OPT_L);
getToolChain().AddFilePathLibArgs(Args, CmdArgs);
@@ -633,7 +634,7 @@ void amdgpu::Linker::ConstructJob(Compilation &C, const JobAction &JA,
const bool ThinLTO = (C.getDriver().getLTOMode() == LTOK_Thin);
addLTOOptions(getToolChain(), Args, CmdArgs, Output, Inputs[0], ThinLTO);
- if (!ThinLTO)
+ if (!ThinLTO && JA.getOffloadingDeviceKind() == Action::OFK_HIP)
addFullLTOPartitionOption(C.getDriver(), Args, CmdArgs);
} else if (Args.hasArg(options::OPT_mcpu_EQ)) {
CmdArgs.push_back(Args.MakeArgString(
@@ -712,14 +713,12 @@ void amdgpu::getAMDGPUTargetFeatures(const Driver &D,
}
static unsigned getFullLTOPartitions(const Driver &D, const ArgList &Args) {
- const Arg *A = Args.getLastArg(options::OPT_flto_partitions_EQ);
- // In the absence of an option, use 8 as the default.
- if (!A)
- return 8;
int Value = 0;
- if (StringRef(A->getValue()).getAsInteger(10, Value) || (Value < 1)) {
+ StringRef A = Args.getLastArgValue(options::OPT_flto_partitions_EQ, "8");
+ if (A.getAsInteger(10, Value) || (Value < 1)) {
+ Arg *Arg = Args.getLastArg(options::OPT_flto_partitions_EQ);
D.Diag(diag::err_drv_invalid_int_value)
- << A->getAsString(Args) << A->getValue();
+ << Arg->getAsString(Args) << Arg->getValue();
return 1;
}
@@ -729,13 +728,8 @@ static unsigned getFullLTOPartitions(const Driver &D, const ArgList &Args) {
void amdgpu::addFullLTOPartitionOption(const Driver &D,
const llvm::opt::ArgList &Args,
llvm::opt::ArgStringList &CmdArgs) {
- // TODO: Should this be restricted to fgpu-rdc only ? Currently we'll
- // also do it for non gpu-rdc LTO
-
- if (unsigned NumParts = getFullLTOPartitions(D, Args); NumParts > 1) {
- CmdArgs.push_back(
- Args.MakeArgString("--lto-partitions=" + Twine(NumParts)));
- }
+ CmdArgs.push_back(Args.MakeArgString("--lto-partitions=" +
+ Twine(getFullLTOPartitions(D, Args))));
}
/// AMDGPU Toolchain
diff --git a/clang/test/Driver/amdgpu-toolchain.c b/clang/test/Driver/amdgpu-toolchain.c
index 6617108e59fcf..20656f1fadeb7 100644
--- a/clang/test/Driver/amdgpu-toolchain.c
+++ b/clang/test/Driver/amdgpu-toolchain.c
@@ -21,7 +21,7 @@
// RUN: %clang -### --target=amdgcn-amd-amdhsa -mcpu=gfx90a:xnack+:sramecc- -nogpulib \
// RUN: -L. -flto -fconvergent-functions %s 2>&1 | FileCheck -check-prefix=LTO %s
// LTO: clang{{.*}} "-flto=full"{{.*}}"-fconvergent-functions"
-// LTO: ld.lld{{.*}}"-L."{{.*}}"-plugin-opt=mcpu=gfx90a"{{.*}}"--lto-partitions={{[0-9]+}}"{{.*}}"-plugin-opt=-mattr=-sramecc,+xnack"
+// LTO: ld.lld{{.*}}"-L."{{.*}}"-plugin-opt=mcpu=gfx90a"{{.*}}"-plugin-opt=-mattr=-sramecc,+xnack"
// RUN: %clang -### --target=amdgcn-amd-amdhsa -mcpu=gfx90a:xnack+:sramecc- -nogpulib \
// RUN: -L. -fconvergent-functions %s 2>&1 | FileCheck -check-prefix=MCPU %s
@@ -38,17 +38,3 @@
// RUN: %clang -target amdgcn-amd-amdhsa -march=gfx90a -stdlib -startfiles \
// RUN: -nogpulib -nogpuinc -### %s 2>&1 | FileCheck -check-prefix=STARTUP %s
// STARTUP: ld.lld{{.*}}"-lc" "-lm" "{{.*}}crt1.o"
-
-// Check --flto-partitions
-
-// RUN: %clang -### --target=amdgcn-amd-amdhsa -mcpu=gfx90a -nogpulib \
-// RUN: -L. -flto --flto-partitions=42 %s 2>&1 | FileCheck -check-prefix=LTO_PARTS %s
-// LTO_PARTS: ld.lld{{.*}}"-L."{{.*}}"-plugin-opt=mcpu=gfx90a"{{.*}}"--lto-partitions=42"
-
-// RUN: not %clang -### --target=amdgcn-amd-amdhsa -mcpu=gfx90a -nogpulib \
-// RUN: -L. -flto --flto-partitions=a %s 2>&1 | FileCheck -check-prefix=LTO_PARTS_INV0 %s
-// LTO_PARTS_INV0: clang: error: invalid integral value 'a' in '--flto-partitions=a'
-
-// RUN: not %clang -### --target=amdgcn-amd-amdhsa -mcpu=gfx90a -nogpulib \
-// RUN: -L. -flto --flto-partitions=0 %s 2>&1 | FileCheck -check-prefix=LTO_PARTS_INV1 %s
-// LTO_PARTS_INV1: clang: error: invalid integral value '0' in '--flto-partitions=0'
diff --git a/libc/startup/gpu/CMakeLists.txt b/libc/startup/gpu/CMakeLists.txt
index a30e6f07a66a3..fa326ef46a9d1 100644
--- a/libc/startup/gpu/CMakeLists.txt
+++ b/libc/startup/gpu/CMakeLists.txt
@@ -33,14 +33,8 @@ function(add_startup_object name)
set_target_properties(${fq_target_name}.exe PROPERTIES
RUNTIME_OUTPUT_DIRECTORY ${LIBC_LIBRARY_DIR}
RUNTIME_OUTPUT_NAME ${name}.o)
- # FIXME: A bug in the AMDGPU LTO pass is incorrectly removing the kernels.
- if(LIBC_TARGET_ARCHITECTURE_IS_NVPTX)
- target_link_options(${fq_target_name}.exe PRIVATE
- "-r" "-nostdlib" "-flto" "-Wl,--lto-emit-llvm")
- else()
- target_link_options(${fq_target_name}.exe PRIVATE
- "-r" "-nostdlib" "-Wl,--lto-emit-llvm")
- endif()
+ target_link_options(${fq_target_name}.exe PRIVATE
+ "-r" "-nostdlib" "-flto" "-Wl,--lto-emit-llvm")
endif()
endfunction()
More information about the libc-commits
mailing list