[SYCL] Enhance device libraries filename check when constructing llvm-link commands (#2944)

We check input files' name when constructing "llvm-link -only-needed" for linking 
SYCL device libraries. Currently, the criteria is:
1. has the prefix 'libsycl-'
2. has the postfix '.o'
Such check is too fragile, this PR aims to enhance the check, input SYCL device
libraries' filename pattern is "libsycl-${pure-name}-$random.o" where
${pure-name} is in list {'crt', 'cmath', 'cmath-fp64', 'complex', 'complex-fp64',
'fallback-cassert', 'fallback-cmath', 'fallback-cmath-fp64', 'fallback-complex', 
'fallback-complex-fp64'} and ${random} is a random string,
so the updated criteria is:
1. has the prefix 'libsycl-'
2. has the postfix '.o'
3. includes at least 2 '-' character in the filename
4. the 'pure name' extracted from the input filename should be in sycl device
    library 'pure name' list.
5. Input file list includes 2 files at least(when using llvm-link -only-needed, we
    will put user's device code and several sycl device libraries into input list
    which means there are 2 input files at least)

This enhancement can only mitigate the fragility since the check is still based
on filename. If we switch to approach of "-mlink-builtin-bitcode" for SYCL
device library link in the future, this problem will be gone automatically.

Signed-off-by: gejin <[email protected]>

Author: jinge90

clang/lib/Driver/ToolChains/SYCL.cpp

@@ -95,6 +95,21 @@ void SYCL::constructLLVMForeachCommand(Compilation &C, const JobAction &JA,
                                          Foreach, ForeachArgs, None));
 }
 
+// The list should match pre-built SYCL device library files located in
+// compiler package. Once we add or remove any SYCL device library files,
+// the list should be updated accordingly.
+static llvm::SmallVector<StringRef, 10> SYCLDeviceLibList{
+    "crt",
+    "cmath",
+    "cmath-fp64",
+    "complex",
+    "complex-fp64",
+    "fallback-cassert",
+    "fallback-cmath",
+    "fallback-cmath-fp64",
+    "fallback-complex",
+    "fallback-complex-fp64"};
+
 const char *SYCL::Linker::constructLLVMLinkCommand(
     Compilation &C, const JobAction &JA, const InputInfo &Output,
     const ArgList &Args, StringRef SubArchName, StringRef OutputFilePrefix,
@@ -116,16 +131,32 @@ const char *SYCL::Linker::constructLLVMLinkCommand(
   // an actual object/archive.  Take that list and pass those to the linker
   // instead of the original object.
   if (JA.isDeviceOffloading(Action::OFK_SYCL)) {
-    auto SYCLDeviceLibIter =
-        std::find_if(InputFiles.begin(), InputFiles.end(), [](const auto &II) {
-          StringRef InputFilename =
-              llvm::sys::path::filename(StringRef(II.getFilename()));
-          if (InputFilename.startswith("libsycl-") &&
-              InputFilename.endswith(".o"))
-            return true;
-          return false;
-        });
-    bool LinkSYCLDeviceLibs = (SYCLDeviceLibIter != InputFiles.end());
+    auto isSYCLDeviceLib = [&C](const InputInfo &II) {
+      const ToolChain *HostTC = C.getSingleOffloadToolChain<Action::OFK_Host>();
+      StringRef LibPostfix = ".o";
+      if (HostTC->getTriple().isWindowsMSVCEnvironment() &&
+          C.getDriver().IsCLMode())
+        LibPostfix = ".obj";
+      StringRef InputFilename =
+          llvm::sys::path::filename(StringRef(II.getFilename()));
+      if (!InputFilename.startswith("libsycl-") ||
+          !InputFilename.endswith(LibPostfix) || (InputFilename.count('-') < 2))
+        return false;
+      size_t PureLibNameLen = InputFilename.find_last_of('-');
+      // Skip the prefix "libsycl-"
+      StringRef PureLibName = InputFilename.substr(8, PureLibNameLen - 8);
+      for (const auto &L : SYCLDeviceLibList) {
+        if (PureLibName.compare(L) == 0)
+          return true;
+      }
+      return false;
+    };
+    size_t InputFileNum = InputFiles.size();
+    bool LinkSYCLDeviceLibs = (InputFileNum >= 2);
+    LinkSYCLDeviceLibs = LinkSYCLDeviceLibs && !isSYCLDeviceLib(InputFiles[0]);
+    for (size_t Idx = 1; Idx < InputFileNum; ++Idx)
+      LinkSYCLDeviceLibs =
+          LinkSYCLDeviceLibs && isSYCLDeviceLib(InputFiles[Idx]);
     // Go through the Inputs to the link.  When a listfile is encountered, we
     // know it is an unbundled generated list.
     if (LinkSYCLDeviceLibs)

clang/test/Driver/sycl-device-lib.cpp

@@ -122,3 +122,11 @@
 // SYCL_LLVM_LINK_NO_DEVICE_LIB: clang{{.*}} "-cc1" {{.*}} "-fsycl-is-device"
 // SYCL_LLVM_LINK_NO_DEVICE_LIB-NOT: llvm-link{{.*}}  "-only-needed"
 // SYCL_LLVM_LINK_NO_DEVICE_LIB: sycl-post-link{{.*}}  "-symbols" "-spec-const=rt" "-o" "{{.*}}.table" "{{.*}}.bc"
+
+/// ###########################################################################
+/// test llvm-link behavior for special user input whose filename resembles SYCL device library
+// RUN: touch libsycl-crt.o
+// RUN: %clangxx -fsycl libsycl-crt.o -### 2>&1 \
+// RUN:   | FileCheck %s -check-prefix=SYCL_LLVM_LINK_USER_ONLY_NEEDED
+// SYCL_LLVM_LINK_USER_ONLY_NEEDED: llvm-link{{.*}}  "{{.*}}.o" "-o" "{{.*}}.bc" "--suppress-warnings"
+// SYCL_LLVM_LINK_USER_ONLY_NEEDED: llvm-link{{.*}}  "-only-needed" "{{.*}}" "-o" "{{.*}}.bc" "--suppress-warnings"