[SPIR-V] Prefer llvm-spirv-<LLVM_VERSION_MAJOR> tool (#77897)

Prefer using `llvm-spirv-<LLVM_VERSION_MAJOR>` tool (i.e.
`llvm-spirv-18`) over plain `llvm-spirv`. If the versioned tool is not
found in PATH, fall back to use the plain `llvm-spirv`.

An issue with the using `llvm-spirv` is that the one found in PATH might
be compiled against older LLVM version which could lead to crashes or
obscure bugs. For example, `llvm-spirv` distributed by Ubuntu links
against different LLVM version depending on the Ubuntu release (LLVM-10
in 20.04LTS, LLVM-13 in 22.04LTS).

clang/docs/UsersManual.rst

@@ -4430,9 +4430,9 @@ To generate SPIR-V binaries, Clang uses the external ``llvm-spirv`` tool from th
 Prior to the generation of SPIR-V binary with Clang, ``llvm-spirv``
 should be built or installed. Please refer to `the following instructions
 <https://github.com/KhronosGroup/SPIRV-LLVM-Translator#build-instructions>`_
-for more details. Clang will expect the ``llvm-spirv`` executable to
-be present in the ``PATH`` environment variable. Clang uses ``llvm-spirv``
-with `the widely adopted assembly syntax package
+for more details. Clang will look for ``llvm-spirv-<LLVM-major-version>`` and
+``llvm-spirv`` executables, in this order, in the ``PATH`` environment variable.
+Clang uses ``llvm-spirv`` with `the widely adopted assembly syntax package
 <https://github.com/KhronosGroup/SPIRV-LLVM-Translator/#build-with-spirv-tools>`_.
 
 `The versioning

clang/lib/Driver/ToolChains/SPIRV.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 #include "SPIRV.h"
 #include "CommonArgs.h"
+#include "clang/Basic/Version.h"
 #include "clang/Driver/Compilation.h"
 #include "clang/Driver/Driver.h"
 #include "clang/Driver/InputInfo.h"
@@ -32,8 +33,15 @@ void SPIRV::constructTranslateCommand(Compilation &C, const Tool &T,
 
   CmdArgs.append({"-o", Output.getFilename()});
 
-  const char *Exec =
-      C.getArgs().MakeArgString(T.getToolChain().GetProgramPath("llvm-spirv"));
+  // Try to find "llvm-spirv-<LLVM_VERSION_MAJOR>". Otherwise, fall back to
+  // plain "llvm-spirv".
+  using namespace std::string_literals;
+  auto VersionedTool = "llvm-spirv-"s + std::to_string(LLVM_VERSION_MAJOR);
+  std::string ExeCand = T.getToolChain().GetProgramPath(VersionedTool.c_str());
+  if (!llvm::sys::fs::can_execute(ExeCand))
+    ExeCand = T.getToolChain().GetProgramPath("llvm-spirv");
+
+  const char *Exec = C.getArgs().MakeArgString(ExeCand);
   C.addCommand(std::make_unique<Command>(JA, T, ResponseFileSupport::None(),
                                          Exec, CmdArgs, Input, Output));
 }

clang/test/Driver/hipspv-toolchain.hip

@@ -34,3 +34,16 @@
 // CHECK-SAME: "-o" [[OBJ_HOST:".*o"]] "-x" "hip"
 
 // CHECK: {{".*ld.*"}} {{.*}}[[OBJ_HOST]]
+
+//-----------------------------------------------------------------------------
+// Check llvm-spirv-<LLVM_VERSION_MAJOR> is used if it is found in PATH.
+// RUN: mkdir -p %t/versioned
+// RUN: touch %t/versioned/llvm-spirv-%llvm-version-major \
+// RUN:   && chmod +x %t/versioned/llvm-spirv-%llvm-version-major
+// RUN: env "PATH=%t/versioned" %clang -### -target x86_64-linux-gnu \
+// RUN:   --offload=spirv64 --hip-path=%S/Inputs/hipspv -nohipwrapperinc \
+// RUN:   %s 2>&1 \
+// RUN:   | FileCheck -DVERSION=%llvm-version-major \
+// RUN:   --check-prefix=VERSIONED %s
+
+// VERSIONED: {{.*}}llvm-spirv-[[VERSION]]

clang/test/Driver/spirv-toolchain.cl

@@ -77,3 +77,13 @@
 
 // XTOR: {{llvm-spirv.*"}}
 // BACKEND-NOT: {{llvm-spirv.*"}}
+
+//-----------------------------------------------------------------------------
+// Check llvm-spirv-<LLVM_VERSION_MAJOR> is used if it is found in PATH.
+// RUN: mkdir -p %t/versioned
+// RUN: touch %t/versioned/llvm-spirv-%llvm-version-major \
+// RUN:   && chmod +x %t/versioned/llvm-spirv-%llvm-version-major
+// RUN: env "PATH=%t/versioned" %clang -### --target=spirv64 -x cl -c %s 2>&1 \
+// RUN:   | FileCheck -DVERSION=%llvm-version-major --check-prefix=VERSIONED %s
+
+// VERSIONED: {{.*}}llvm-spirv-[[VERSION]]

clang/test/lit.site.cfg.py.in

@@ -43,6 +43,7 @@ config.llvm_external_lit = path(r"@LLVM_EXTERNAL_LIT@")
 config.standalone_build = @CLANG_BUILT_STANDALONE@
 config.ppc_linux_default_ieeelongdouble = @PPC_LINUX_DEFAULT_IEEELONGDOUBLE@
 config.have_llvm_driver = @LLVM_TOOL_LLVM_DRIVER_BUILD@
+config.substitutions.append(("%llvm-version-major", "@LLVM_VERSION_MAJOR@"))
 
 import lit.llvm
 lit.llvm.initialize(lit_config, config)