[clang] [Clang] Add multilib support for GPU targets (PR #192285)
Joseph Huber via cfe-commits
cfe-commits at lists.llvm.org
Wed Apr 15 09:40:36 PDT 2026
https://github.com/jhuber6 created https://github.com/llvm/llvm-project/pull/192285
Summary:
This PR uses the new, generic multilib support added in https://github.com/llvm/llvm-project/pull/188584
to also function for GPU targets. This will allow toolchains to easy
provide variants of these GPU libraries (for debug or asan). In
practice, this will look something like this:
```console
-DRUNTIMES_amdgcn-amd-amdhsa+debug_CMAKE_BUILD_TYPE=Debug \
-DRUNTIMES_amdgcn-amd-amdhsa+debug_LIBOMPTARGET_ENABLE_DEBUG=ON \
-DRUNTIMES_amdgcn-amd-amdhsa+debug_LLVM_ENABLE_RUNTIMES=openmp \
-DLLVM_RUNTIME_MULTILIBS=debug \
-DLLVM_RUNTIME_MULTILIB_debug_TARGETS="amdgcn-amd-amdhsa" \
```
This will then install it into the tree like this:
```
<install>/lib/amdgcn-amd-amdhsa/debug/libompdevice.a
```
The user can then activate this like the following (assuming they have a
multilib.yaml in the library directory):
```
clang input.c -fopenmp --offload-arch=gfx942 -fmultilib-flag=debug
```
>From 1b1e6279798e3a9b11696c43bb79015c964dfc04 Mon Sep 17 00:00:00 2001
From: Joseph Huber <huberjn at outlook.com>
Date: Wed, 15 Apr 2026 11:34:47 -0500
Subject: [PATCH] [Clang] Add multilib support for GPU targets
Summary:
This PR uses the new, generic multilib support added in https://github.com/llvm/llvm-project/pull/188584
to also function for GPU targets. This will allow toolchains to easy
provide variants of these GPU libraries (for debug or asan). In
practice, this will look something like this:
```console
-DRUNTIMES_amdgcn-amd-amdhsa+debug_CMAKE_BUILD_TYPE=Debug \
-DRUNTIMES_amdgcn-amd-amdhsa+debug_LIBOMPTARGET_ENABLE_DEBUG=ON \
-DRUNTIMES_amdgcn-amd-amdhsa+debug_LLVM_ENABLE_RUNTIMES=openmp \
-DLLVM_RUNTIME_MULTILIBS=debug \
-DLLVM_RUNTIME_MULTILIB_debug_TARGETS="amdgcn-amd-amdhsa" \
```
This will then install it into the tree like this:
```
<install>/lib/amdgcn-amd-amdhsa/debug/libompdevice.a
```
The user can then activate this like the following (assuming they have a
multilib.yaml in the library directory):
```
clang input.c -fopenmp --offload-arch=gfx942 -fmultilib-flag=debug
```
---
clang/lib/Driver/ToolChains/AMDGPU.cpp | 14 +++++
clang/lib/Driver/ToolChains/Clang.cpp | 1 +
clang/lib/Driver/ToolChains/Cuda.cpp | 16 +++++-
clang/test/Driver/amdgpu-multilib.yaml | 80 ++++++++++++++++++++++++++
clang/test/Driver/nvptx-multilib.yaml | 80 ++++++++++++++++++++++++++
5 files changed, 190 insertions(+), 1 deletion(-)
create mode 100644 clang/test/Driver/amdgpu-multilib.yaml
create mode 100644 clang/test/Driver/nvptx-multilib.yaml
diff --git a/clang/lib/Driver/ToolChains/AMDGPU.cpp b/clang/lib/Driver/ToolChains/AMDGPU.cpp
index b72d0e68f63f0..ff4c781d51348 100644
--- a/clang/lib/Driver/ToolChains/AMDGPU.cpp
+++ b/clang/lib/Driver/ToolChains/AMDGPU.cpp
@@ -700,6 +700,8 @@ AMDGPUToolChain::AMDGPUToolChain(const Driver &D, const llvm::Triple &Triple,
: Generic_ELF(D, Triple, Args),
OptionsDefault(
{{options::OPT_O, "3"}, {options::OPT_cl_std_EQ, "CL1.2"}}) {
+ loadMultilibsFromYAML(Args, D);
+
// Check code object version options. Emit warnings for legacy options
// and errors for the last invalid code object version options.
// It is done here to avoid repeated warning or error messages for
@@ -881,6 +883,18 @@ void AMDGPUToolChain::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
DriverArgs.hasArg(options::OPT_nostdlibinc))
return;
+ // Add multilib variant include paths in priority order.
+ for (const Multilib &M : getOrderedMultilibs()) {
+ if (M.isDefault())
+ continue;
+ if (std::optional<std::string> StdlibIncDir = getStdlibIncludePath()) {
+ SmallString<128> Dir(*StdlibIncDir);
+ llvm::sys::path::append(Dir, M.includeSuffix());
+ if (getDriver().getVFS().exists(Dir))
+ addSystemInclude(DriverArgs, CC1Args, Dir);
+ }
+ }
+
if (std::optional<std::string> Path = getStdlibIncludePath())
addSystemInclude(DriverArgs, CC1Args, *Path);
}
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index f685abe9dad35..bab076fbfa793 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -9422,6 +9422,7 @@ void LinkerWrapper::ConstructJob(Compilation &C, const JobAction &JA,
OPT_flto_EQ,
OPT_hipspv_pass_plugin_EQ,
OPT_use_spirv_backend,
+ OPT_fmultilib_flag,
OPT_fprofile_generate,
OPT_fprofile_generate_EQ,
OPT_fprofile_instr_generate,
diff --git a/clang/lib/Driver/ToolChains/Cuda.cpp b/clang/lib/Driver/ToolChains/Cuda.cpp
index dc94fca06db7d..dcde82cdf4d85 100644
--- a/clang/lib/Driver/ToolChains/Cuda.cpp
+++ b/clang/lib/Driver/ToolChains/Cuda.cpp
@@ -742,7 +742,9 @@ NVPTXToolChain::NVPTXToolChain(const Driver &D, const llvm::Triple &Triple,
/// system's default triple if not provided.
NVPTXToolChain::NVPTXToolChain(const Driver &D, const llvm::Triple &Triple,
const ArgList &Args)
- : NVPTXToolChain(D, Triple, llvm::Triple(LLVM_HOST_TRIPLE), Args) {}
+ : NVPTXToolChain(D, Triple, llvm::Triple(LLVM_HOST_TRIPLE), Args) {
+ loadMultilibsFromYAML(Args, D);
+}
llvm::opt::DerivedArgList *
NVPTXToolChain::TranslateArgs(const llvm::opt::DerivedArgList &Args,
@@ -792,6 +794,18 @@ void NVPTXToolChain::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
DriverArgs.hasArg(options::OPT_nostdlibinc))
return;
+ // Add multilib variant include paths in priority order.
+ for (const Multilib &M : getOrderedMultilibs()) {
+ if (M.isDefault())
+ continue;
+ if (std::optional<std::string> StdlibIncDir = getStdlibIncludePath()) {
+ SmallString<128> Dir(*StdlibIncDir);
+ llvm::sys::path::append(Dir, M.includeSuffix());
+ if (getDriver().getVFS().exists(Dir))
+ addSystemInclude(DriverArgs, CC1Args, Dir);
+ }
+ }
+
if (std::optional<std::string> Path = getStdlibIncludePath())
addSystemInclude(DriverArgs, CC1Args, *Path);
}
diff --git a/clang/test/Driver/amdgpu-multilib.yaml b/clang/test/Driver/amdgpu-multilib.yaml
new file mode 100644
index 0000000000000..8c5714aa29c25
--- /dev/null
+++ b/clang/test/Driver/amdgpu-multilib.yaml
@@ -0,0 +1,80 @@
+# UNSUPPORTED: system-windows
+
+# Basic selection where -fmultilib-flag=debug selects the debug variant.
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -x c %s -### -o /dev/null 2>&1 \
+# RUN: --target=amdgcn-amd-amdhsa -mcpu=gfx1030 -fmultilib-flag=debug -nogpulib \
+# RUN: | FileCheck --check-prefix=CHECK-DEBUG %s
+# CHECK-DEBUG: "-cc1" "-triple" "amdgcn-amd-amdhsa"
+# CHECK-DEBUG: "-L{{[^"]*}}/debug"
+
+# Default behavior where no variant path is prepended.
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -x c %s -### -o /dev/null 2>&1 \
+# RUN: --target=amdgcn-amd-amdhsa -mcpu=gfx1030 -nogpulib \
+# RUN: | FileCheck --check-prefix=CHECK-DEFAULT %s
+# CHECK-DEFAULT-NOT: "-L{{[^"]*}}/debug"
+# CHECK-DEFAULT-NOT: "-L{{[^"]*}}/release"
+# CHECK-DEFAULT-NOT: "-L{{[^"]*}}/noexcept"
+
+# Multiple matches stacking on top of each-other.
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -x c %s -### -o /dev/null 2>&1 \
+# RUN: --target=amdgcn-amd-amdhsa -mcpu=gfx1030 -fmultilib-flag=debug -fno-exceptions -nogpulib \
+# RUN: | FileCheck --check-prefix=CHECK-LAYERED %s
+# CHECK-LAYERED: "-L{{[^"]*}}/noexcept"
+# CHECK-LAYERED-SAME: "-L{{[^"]*}}/debug"
+
+# Lists selected variant directories.
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-directory 2>&1 \
+# RUN: --target=amdgcn-amd-amdhsa -mcpu=gfx1030 -fmultilib-flag=debug \
+# RUN: | FileCheck --check-prefix=CHECK-PRINT-DIR %s
+# CHECK-PRINT-DIR: debug
+
+# Lists all non-default variants with flags.
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-lib 2>&1 \
+# RUN: --target=amdgcn-amd-amdhsa -mcpu=gfx1030 \
+# RUN: | FileCheck --check-prefix=CHECK-PRINT-LIB %s
+# CHECK-PRINT-LIB: debug;@fmultilib-flag=debug
+# CHECK-PRINT-LIB: release;@fmultilib-flag=release
+# CHECK-PRINT-LIB: noexcept;@fno-exceptions
+
+# Error emitted when custom flag value is invalid.
+# RUN: not %clang --multi-lib-config=%s -no-canonical-prefixes -x c %s -### -o /dev/null 2>&1 \
+# RUN: --target=amdgcn-amd-amdhsa -mcpu=gfx1030 -fmultilib-flag=nonexistent -nogpulib \
+# RUN: | FileCheck --check-prefix=CHECK-NOMATCH %s
+# CHECK-NOMATCH: error: unsupported option '-fmultilib-flag=nonexistent'
+
+# Check exclusivity so that only one of debug/release selected.
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-directory 2>&1 \
+# RUN: --target=amdgcn-amd-amdhsa -mcpu=gfx1030 -fmultilib-flag=release \
+# RUN: | FileCheck --check-prefix=CHECK-EXCLUSIVE %s
+# CHECK-EXCLUSIVE: release
+# CHECK-EXCLUSIVE-NOT: debug
+
+---
+MultilibVersion: 1.0
+
+Groups:
+- Name: build-type
+ Type: Exclusive
+
+Variants:
+- Dir: .
+ Flags: []
+- Dir: debug
+ Flags: [-fmultilib-flag=debug]
+ Group: build-type
+- Dir: release
+ Flags: [-fmultilib-flag=release]
+ Group: build-type
+- Dir: noexcept
+ Flags: [-fno-exceptions]
+
+Mappings: []
+
+Flags:
+- Name: build-type
+ Values:
+ - Name: none
+ - Name: debug
+ - Name: release
+ Default: none
+...
diff --git a/clang/test/Driver/nvptx-multilib.yaml b/clang/test/Driver/nvptx-multilib.yaml
new file mode 100644
index 0000000000000..d4b5de67cb90b
--- /dev/null
+++ b/clang/test/Driver/nvptx-multilib.yaml
@@ -0,0 +1,80 @@
+# UNSUPPORTED: system-windows
+
+# Basic selection where -fmultilib-flag=debug selects the debug variant.
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -x c %s -### -o /dev/null 2>&1 \
+# RUN: --target=nvptx64-nvidia-cuda -march=sm_52 -fmultilib-flag=debug -nogpulib \
+# RUN: | FileCheck --check-prefix=CHECK-DEBUG %s
+# CHECK-DEBUG: "-cc1" "-triple" "nvptx64-nvidia-cuda"
+# CHECK-DEBUG: "-L{{[^"]*}}/debug"
+
+# Default behavior where no variant path is prepended.
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -x c %s -### -o /dev/null 2>&1 \
+# RUN: --target=nvptx64-nvidia-cuda -march=sm_52 -nogpulib \
+# RUN: | FileCheck --check-prefix=CHECK-DEFAULT %s
+# CHECK-DEFAULT-NOT: "-L{{[^"]*}}/debug"
+# CHECK-DEFAULT-NOT: "-L{{[^"]*}}/release"
+# CHECK-DEFAULT-NOT: "-L{{[^"]*}}/noexcept"
+
+# Multiple matches stacking on top of each-other.
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -x c %s -### -o /dev/null 2>&1 \
+# RUN: --target=nvptx64-nvidia-cuda -march=sm_52 -fmultilib-flag=debug -fno-exceptions -nogpulib \
+# RUN: | FileCheck --check-prefix=CHECK-LAYERED %s
+# CHECK-LAYERED: "-L{{[^"]*}}/noexcept"
+# CHECK-LAYERED-SAME: "-L{{[^"]*}}/debug"
+
+# Lists selected variant directories.
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-directory 2>&1 \
+# RUN: --target=nvptx64-nvidia-cuda -march=sm_52 -fmultilib-flag=debug \
+# RUN: | FileCheck --check-prefix=CHECK-PRINT-DIR %s
+# CHECK-PRINT-DIR: debug
+
+# Lists all non-default variants with flags.
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-lib 2>&1 \
+# RUN: --target=nvptx64-nvidia-cuda -march=sm_52 \
+# RUN: | FileCheck --check-prefix=CHECK-PRINT-LIB %s
+# CHECK-PRINT-LIB: debug;@fmultilib-flag=debug
+# CHECK-PRINT-LIB: release;@fmultilib-flag=release
+# CHECK-PRINT-LIB: noexcept;@fno-exceptions
+
+# Error emitted when custom flag value is invalid.
+# RUN: not %clang --multi-lib-config=%s -no-canonical-prefixes -x c %s -### -o /dev/null 2>&1 \
+# RUN: --target=nvptx64-nvidia-cuda -march=sm_52 -fmultilib-flag=nonexistent -nogpulib \
+# RUN: | FileCheck --check-prefix=CHECK-NOMATCH %s
+# CHECK-NOMATCH: error: unsupported option '-fmultilib-flag=nonexistent'
+
+# Check exclusivity so that only one of debug/release selected.
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-directory 2>&1 \
+# RUN: --target=nvptx64-nvidia-cuda -march=sm_52 -fmultilib-flag=release \
+# RUN: | FileCheck --check-prefix=CHECK-EXCLUSIVE %s
+# CHECK-EXCLUSIVE: release
+# CHECK-EXCLUSIVE-NOT: debug
+
+---
+MultilibVersion: 1.0
+
+Groups:
+- Name: build-type
+ Type: Exclusive
+
+Variants:
+- Dir: .
+ Flags: []
+- Dir: debug
+ Flags: [-fmultilib-flag=debug]
+ Group: build-type
+- Dir: release
+ Flags: [-fmultilib-flag=release]
+ Group: build-type
+- Dir: noexcept
+ Flags: [-fno-exceptions]
+
+Mappings: []
+
+Flags:
+- Name: build-type
+ Values:
+ - Name: none
+ - Name: debug
+ - Name: release
+ Default: none
+...
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