https://github.com/Pierre-vh created
https://github.com/llvm/llvm-project/pull/128509
The default number of partitions is the number of cores on the machine with a
cap at 16, as going above 16 is unlikely to be useful in the common case.
Adds a flto-partitions option to override the number of partitions easily
(without having to use -Xoffload-linker). Setting it to 1 effectively disables
module splitting.
Fixes SWDEV-506214
>From e58e1b4e324150e913f9c80a467b8f9a349d1bdc Mon Sep 17 00:00:00 2001
From: pvanhout <pierre.vanhoutr...@amd.com>
Date: Mon, 24 Feb 2025 14:21:49 +0100
Subject: [PATCH] [clang][AMDGPU] Enable module splitting by default
The default number of partitions is the number of cores on the machine with a
cap at 16, as going above 16 is unlikely to be useful in the common case.
Adds a flto-partitions option to override the number of partitions easily
(without having to use -Xoffload-linker). Setting it to 1 effectively disables
module splitting.
Fixes SWDEV-506214
---
clang/include/clang/Driver/Options.td | 6 ++--
clang/lib/Driver/ToolChains/AMDGPU.cpp | 36 +++++++++++++++++--
clang/lib/Driver/ToolChains/AMDGPU.h | 2 ++
clang/lib/Driver/ToolChains/HIPAMD.cpp | 2 ++
clang/test/Driver/amdgpu-toolchain.c | 20 +++++++++--
.../hip-toolchain-rdc-flto-partitions.hip | 35 ++++++++++++++++++
.../Driver/hip-toolchain-rdc-static-lib.hip | 2 ++
clang/test/Driver/hip-toolchain-rdc.hip | 1 +
8 files changed, 98 insertions(+), 6 deletions(-)
create mode 100644 clang/test/Driver/hip-toolchain-rdc-flto-partitions.hip
diff --git a/clang/include/clang/Driver/Options.td
b/clang/include/clang/Driver/Options.td
index e521cbf678d93..6cb2fd1b755c1 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1393,6 +1393,8 @@ def fhip_emit_relocatable : Flag<["-"],
"fhip-emit-relocatable">,
HelpText<"Compile HIP source to relocatable">;
def fno_hip_emit_relocatable : Flag<["-"], "fno-hip-emit-relocatable">,
HelpText<"Do not override toolchain to compile HIP source to relocatable">;
+def flto_partitions_EQ : Joined<["--"], "flto-partitions=">, Group<hip_Group>,
+ HelpText<"Number of partitions to use for parallel full LTO codegen. Use 1
to disable partitioning.">;
}
// Clang specific/exclusive options for OpenACC.
@@ -3158,7 +3160,7 @@ def modules_reduced_bmi : Flag<["-"],
"fmodules-reduced-bmi">,
HelpText<"Generate the reduced BMI">,
MarshallingInfoFlag<FrontendOpts<"GenReducedBMI">>;
-def experimental_modules_reduced_bmi : Flag<["-"],
"fexperimental-modules-reduced-bmi">,
+def experimental_modules_reduced_bmi : Flag<["-"],
"fexperimental-modules-reduced-bmi">,
Group<f_Group>, Visibility<[ClangOption, CC1Option]>,
Alias<modules_reduced_bmi>;
def fmodules_embed_all_files : Joined<["-"], "fmodules-embed-all-files">,
@@ -7417,7 +7419,7 @@ def fuse_register_sized_bitfield_access: Flag<["-"],
"fuse-register-sized-bitfie
def relaxed_aliasing : Flag<["-"], "relaxed-aliasing">,
HelpText<"Turn off Type Based Alias Analysis">,
MarshallingInfoFlag<CodeGenOpts<"RelaxedAliasing">>;
-defm pointer_tbaa: BoolOption<"", "pointer-tbaa", CodeGenOpts<"PointerTBAA">,
+defm pointer_tbaa: BoolOption<"", "pointer-tbaa", CodeGenOpts<"PointerTBAA">,
DefaultTrue,
PosFlag<SetTrue, [], [ClangOption], "Enable">,
NegFlag<SetFalse, [], [ClangOption], "Disable">,
diff --git a/clang/lib/Driver/ToolChains/AMDGPU.cpp
b/clang/lib/Driver/ToolChains/AMDGPU.cpp
index 6a35a2feabc9b..820a335a4b384 100644
--- a/clang/lib/Driver/ToolChains/AMDGPU.cpp
+++ b/clang/lib/Driver/ToolChains/AMDGPU.cpp
@@ -21,6 +21,7 @@
#include "llvm/Support/LineIterator.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Process.h"
+#include "llvm/Support/Threading.h"
#include "llvm/Support/VirtualFileSystem.h"
#include "llvm/TargetParser/Host.h"
#include <optional>
@@ -630,8 +631,11 @@ void amdgpu::Linker::ConstructJob(Compilation &C, const
JobAction &JA,
getToolChain().AddFilePathLibArgs(Args, CmdArgs);
AddLinkerInputs(getToolChain(), Inputs, Args, CmdArgs, JA);
if (C.getDriver().isUsingLTO()) {
- addLTOOptions(getToolChain(), Args, CmdArgs, Output, Inputs[0],
- C.getDriver().getLTOMode() == LTOK_Thin);
+ const bool ThinLTO = (C.getDriver().getLTOMode() == LTOK_Thin);
+ addLTOOptions(getToolChain(), Args, CmdArgs, Output, Inputs[0], ThinLTO);
+
+ if (!ThinLTO)
+ addFullLTOPartitionOption(C.getDriver(), Args, CmdArgs);
} else if (Args.hasArg(options::OPT_mcpu_EQ)) {
CmdArgs.push_back(Args.MakeArgString(
"-plugin-opt=mcpu=" +
@@ -708,6 +712,34 @@ void amdgpu::getAMDGPUTargetFeatures(const Driver &D,
options::OPT_m_amdgpu_Features_Group);
}
+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 the number of available threads with a
cap
+ // at 16 partitions. More than 16 partitions rarely benefits code splitting
+ // and can lead to more empty/small modules each with their own overhead.
+ if (!A)
+ return std::max(16u, llvm::hardware_concurrency().compute_thread_count());
+ int Value;
+ if (StringRef(A->getValue()).getAsInteger(10, Value) || (Value < 1)) {
+ D.Diag(diag::err_drv_invalid_int_value)
+ << A->getAsString(Args) << A->getValue();
+ return 1;
+ }
+
+ return Value;
+}
+
+void amdgpu::addFullLTOPartitionOption(const Driver &D,
+ const llvm::opt::ArgList &Args,
+ llvm::opt::ArgStringList &CmdArgs) {
+ // TODO: restrict to gpu-rdc only?
+
+ if (unsigned NumParts = GetFullLTOPartitions(D, Args); NumParts > 1) {
+ CmdArgs.push_back(
+ Args.MakeArgString("--lto-partitions=" + std::to_string(NumParts)));
+ }
+}
+
/// AMDGPU Toolchain
AMDGPUToolChain::AMDGPUToolChain(const Driver &D, const llvm::Triple &Triple,
const ArgList &Args)
diff --git a/clang/lib/Driver/ToolChains/AMDGPU.h
b/clang/lib/Driver/ToolChains/AMDGPU.h
index bc941a40445ad..08bd4fa556f78 100644
--- a/clang/lib/Driver/ToolChains/AMDGPU.h
+++ b/clang/lib/Driver/ToolChains/AMDGPU.h
@@ -41,6 +41,8 @@ void getAMDGPUTargetFeatures(const Driver &D, const
llvm::Triple &Triple,
const llvm::opt::ArgList &Args,
std::vector<StringRef> &Features);
+void addFullLTOPartitionOption(const Driver &D, const llvm::opt::ArgList &Args,
+ llvm::opt::ArgStringList &CmdArgs);
} // end namespace amdgpu
} // end namespace tools
diff --git a/clang/lib/Driver/ToolChains/HIPAMD.cpp
b/clang/lib/Driver/ToolChains/HIPAMD.cpp
index 271626ed54aed..4f0511b272a98 100644
--- a/clang/lib/Driver/ToolChains/HIPAMD.cpp
+++ b/clang/lib/Driver/ToolChains/HIPAMD.cpp
@@ -116,6 +116,8 @@ void AMDGCN::Linker::constructLldCommand(Compilation &C,
const JobAction &JA,
addLinkerCompressDebugSectionsOption(TC, Args, LldArgs);
+ amdgpu::addFullLTOPartitionOption(D, Args, LldArgs);
+
// Given that host and device linking happen in separate processes, the
device
// linker doesn't always have the visibility as to which device symbols are
// needed by a program, especially for the device symbol dependencies that
are
diff --git a/clang/test/Driver/amdgpu-toolchain.c
b/clang/test/Driver/amdgpu-toolchain.c
index c1c5aa8e90e68..6617108e59fcf 100644
--- a/clang/test/Driver/amdgpu-toolchain.c
+++ b/clang/test/Driver/amdgpu-toolchain.c
@@ -19,10 +19,12 @@
// AS_LINK_UR: ld.lld{{.*}} "--no-undefined"{{.*}}
"--unresolved-symbols=ignore-all"
// RUN: %clang -### --target=amdgcn-amd-amdhsa -mcpu=gfx90a:xnack+:sramecc-
-nogpulib \
-// RUN: -L. -flto -fconvergent-functions %s 2>&1 | FileCheck
-check-prefixes=LTO,MCPU %s
+// 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"
+
// RUN: %clang -### --target=amdgcn-amd-amdhsa -mcpu=gfx90a:xnack+:sramecc-
-nogpulib \
// RUN: -L. -fconvergent-functions %s 2>&1 | FileCheck -check-prefix=MCPU %s
-// LTO: clang{{.*}} "-flto=full"{{.*}}"-fconvergent-functions"
// MCPU:
ld.lld{{.*}}"-L."{{.*}}"-plugin-opt=mcpu=gfx90a"{{.*}}"-plugin-opt=-mattr=-sramecc,+xnack"
// RUN: %clang -### --target=amdgcn-amd-amdhsa -mcpu=gfx906 -nogpulib \
@@ -36,3 +38,17 @@
// 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/clang/test/Driver/hip-toolchain-rdc-flto-partitions.hip
b/clang/test/Driver/hip-toolchain-rdc-flto-partitions.hip
new file mode 100644
index 0000000000000..e345bd3f5be6b
--- /dev/null
+++ b/clang/test/Driver/hip-toolchain-rdc-flto-partitions.hip
@@ -0,0 +1,35 @@
+// RUN: %clang -### --target=x86_64-linux-gnu \
+// RUN: -x hip --cuda-gpu-arch=gfx803 --flto-partitions=42 \
+// RUN: --no-offload-new-driver --emit-static-lib -nogpulib \
+// RUN: -fuse-ld=lld -B%S/Inputs/lld -fgpu-rdc -nogpuinc \
+// RUN: %S/Inputs/hip_multiple_inputs/a.cu \
+// RUN: %S/Inputs/hip_multiple_inputs/b.hip \
+// RUN: 2>&1 | FileCheck %s --check-prefix=FIXED-PARTS
+
+// FIXED-PARTS-NOT: "*.llvm-link"
+// FIXED-PARTS-NOT: ".*opt"
+// FIXED-PARTS-NOT: ".*llc"
+// FIXED-PARTS: [[LLD: ".*lld.*"]] {{.*}}
"-plugin-opt=-amdgpu-internalize-symbols"
+// FIXED-PARTS-SAME: "-plugin-opt=mcpu=gfx803"
+// FIXED-PARTS-SAME: "--lto-partitions=42"
+// FIXED-PARTS-SAME: "-o" "{{.*out}}" "{{.*bc}}"
+
+// RUN: not %clang -### --target=x86_64-linux-gnu \
+// RUN: -x hip --cuda-gpu-arch=gfx803 --flto-partitions=a \
+// RUN: --no-offload-new-driver --emit-static-lib -nogpulib \
+// RUN: -fuse-ld=lld -B%S/Inputs/lld -fgpu-rdc -nogpuinc \
+// RUN: %S/Inputs/hip_multiple_inputs/a.cu \
+// RUN: %S/Inputs/hip_multiple_inputs/b.hip \
+// RUN: 2>&1 | FileCheck %s --check-prefix=LTO_PARTS_INV0
+
+// LTO_PARTS_INV0: clang: error: invalid integral value 'a' in
'--flto-partitions=a'
+
+// RUN: not %clang -### --target=x86_64-linux-gnu \
+// RUN: -x hip --cuda-gpu-arch=gfx803 --flto-partitions=0 \
+// RUN: --no-offload-new-driver --emit-static-lib -nogpulib \
+// RUN: -fuse-ld=lld -B%S/Inputs/lld -fgpu-rdc -nogpuinc \
+// RUN: %S/Inputs/hip_multiple_inputs/a.cu \
+// RUN: %S/Inputs/hip_multiple_inputs/b.hip \
+// RUN: 2>&1 | FileCheck %s --check-prefix=LTO_PARTS_INV1
+
+// LTO_PARTS_INV1: clang: error: invalid integral value '0' in
'--flto-partitions=0'
diff --git a/clang/test/Driver/hip-toolchain-rdc-static-lib.hip
b/clang/test/Driver/hip-toolchain-rdc-static-lib.hip
index 5276faf31bdc2..6f38a06f7cf31 100644
--- a/clang/test/Driver/hip-toolchain-rdc-static-lib.hip
+++ b/clang/test/Driver/hip-toolchain-rdc-static-lib.hip
@@ -49,6 +49,7 @@
// CHECK-NOT: ".*llc"
// CHECK: [[LLD: ".*lld.*"]] {{.*}} "-plugin-opt=-amdgpu-internalize-symbols"
// CHECK-SAME: "-plugin-opt=mcpu=gfx803"
+// CHECK-SAME: "--lto-partitions={{[0-9]+}}"
// CHECK-SAME: "-o" "[[IMG_DEV1:.*out]]" [[A_BC1]] [[B_BC1]]
// generate image for device side path on gfx900
@@ -77,6 +78,7 @@
// CHECK-NOT: ".*llc"
// CHECK: [[LLD]] {{.*}} "-plugin-opt=-amdgpu-internalize-symbols"
// CHECK-SAME: "-plugin-opt=mcpu=gfx900"
+// CHECK-SAME: "--lto-partitions={{[0-9]+}}"
// CHECK-SAME: "--whole-archive"
// CHECK-SAME: "-o" "[[IMG_DEV2:.*out]]" [[A_BC2]] [[B_BC2]]
// CHECK-SAME: "--no-whole-archive"
diff --git a/clang/test/Driver/hip-toolchain-rdc.hip
b/clang/test/Driver/hip-toolchain-rdc.hip
index 96da423144c1c..9015702e3211a 100644
--- a/clang/test/Driver/hip-toolchain-rdc.hip
+++ b/clang/test/Driver/hip-toolchain-rdc.hip
@@ -147,6 +147,7 @@
// CHECK-NOT: ".*llc"
// CHECK: {{".*lld.*"}} {{.*}} "-plugin-opt=-amdgpu-internalize-symbols"
// CHECK-SAME: "-plugin-opt=mcpu=gfx900"
+// CHECK-SAME: "--lto-partitions={{[0-9]+}}"
// CHECK-SAME: "-o" "[[IMG_DEV2:.*.out]]" [[A_BC2]] [[B_BC2]]
// combine images generated into hip fat binary object
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