[clang][driver] When -fveclib=ArmPL flag is in use, always link against libamath

Using `-fveclib=ArmPL` without libamath likely effects in the
link-time errors.

Author: pawosm-arm

clang/lib/Driver/ToolChains/CommonArgs.cpp

@@ -490,6 +490,39 @@ void tools::AddLinkerInputs(const ToolChain &TC, const InputInfoList &Inputs,
     else
       A.renderAsInput(Args, CmdArgs);
   }
+  if (const Arg *A = Args.getLastArg(options::OPT_fveclib)) {
+    const llvm::Triple &Triple = TC.getTriple();
+    StringRef V = A->getValue();
+    if (V == "ArmPL" && (Triple.isOSLinux() || Triple.isOSDarwin())) {
+      // To support -fveclib=ArmPL we need to link against libamath. Some of the
+      // libamath functions depend on libm, at the same time, libamath exports
+      // its own implementation of some of the libm functions. These are faster
+      // and potentially less accurate implementations, hence we need to be
+      // careful what is being linked in. Since here we are interested only in
+      // the subset of libamath functions that is covered by the veclib
+      // mappings, we need to prioritize libm functions by putting -lm before
+      // -lamath (and then -lm again, to fulfill libamath requirements).
+      //
+      // Therefore we need to do the following:
+      //
+      // 1. On Linux, link only when actually needed.
+      //
+      // 2. Prefer libm functions over libamath.
+      //
+      // 3. Link against libm to resolve libamath dependencies.
+      //
+      if (Triple.isOSLinux()) {
+        CmdArgs.push_back(Args.MakeArgString("--push-state"));
+        CmdArgs.push_back(Args.MakeArgString("--as-needed"));
+      }
+      CmdArgs.push_back(Args.MakeArgString("-lm"));
+      CmdArgs.push_back(Args.MakeArgString("-lamath"));
+      CmdArgs.push_back(Args.MakeArgString("-lm"));
+      if (Triple.isOSLinux())
+        CmdArgs.push_back(Args.MakeArgString("--pop-state"));
+      addArchSpecificRPath(TC, Args, CmdArgs);
+    }
+  }
 }
 
 void tools::addLinkerCompressDebugSectionsOption(

clang/lib/Driver/ToolChains/MSVC.cpp

@@ -84,6 +84,12 @@ void visualstudio::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   else if (TC.getTriple().isWindowsArm64EC())
     CmdArgs.push_back("-machine:arm64ec");
 
+  if (const Arg *A = Args.getLastArg(options::OPT_fveclib)) {
+    StringRef V = A->getValue();
+    if (V == "ArmPL")
+      CmdArgs.push_back(Args.MakeArgString("--dependent-lib=amath"));
+  }
+
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles) &&
       !C.getDriver().IsCLMode() && !C.getDriver().IsFlangMode()) {
     CmdArgs.push_back("-defaultlib:libcmt");

clang/test/Driver/fveclib.c

@@ -112,3 +112,20 @@
 /* Verify no warning when math-errno is re-enabled for a different veclib (that does not imply -fno-math-errno). */
 // RUN: %clang -### --target=aarch64-linux-gnu -fveclib=ArmPL -fmath-errno -fveclib=LIBMVEC %s 2>&1 | FileCheck --check-prefix=CHECK-REPEAT-VECLIB %s
 // CHECK-REPEAT-VECLIB-NOT: math errno enabled
+
+/// Verify that vectorized routines library is being linked in.
+// RUN: %clang -### --target=aarch64-pc-windows-msvc -fveclib=ArmPL %s 2>&1 | FileCheck --check-prefix=CHECK-LINKING-ARMPL-MSVC %s
+// RUN: %clang -### --target=aarch64-linux-gnu -fveclib=ArmPL %s 2>&1 | FileCheck --check-prefix=CHECK-LINKING-ARMPL-LINUX %s
+// RUN: %clang -### --target=aarch64-linux-gnu -fveclib=ArmPL %s -lamath 2>&1 | FileCheck --check-prefix=CHECK-LINKING-AMATH-BEFORE-ARMPL-LINUX %s
+// RUN: %clang -### --target=arm64-apple-darwin -fveclib=ArmPL %s 2>&1 | FileCheck --check-prefix=CHECK-LINKING-ARMPL-DARWIN %s
+// RUN: %clang -### --target=arm64-apple-darwin -fveclib=ArmPL %s -lamath 2>&1 | FileCheck --check-prefix=CHECK-LINKING-AMATH-BEFORE-ARMPL-DARWIN %s
+// CHECK-LINKING-ARMPL-LINUX: "--push-state" "--as-needed" "-lm" "-lamath" "-lm" "--pop-state"
+// CHECK-LINKING-ARMPL-DARWIN: "-lm" "-lamath" "-lm"
+// CHECK-LINKING-ARMPL-MSVC: "--dependent-lib=amath"
+// CHECK-LINKING-AMATH-BEFORE-ARMPL-LINUX: "-lamath" {{.*}}"--push-state" "--as-needed" "-lm" "-lamath" "-lm" "--pop-state"
+// CHECK-LINKING-AMATH-BEFORE-ARMPL-DARWIN: "-lamath" {{.*}}"-lm" "-lamath" "-lm"
+
+/// Verify that the RPATH is being set when needed.
+// RUN: %clang -### --target=aarch64-linux-gnu -resource-dir=%S/../../../clang/test/Driver/Inputs/resource_dir_with_arch_subdir -frtlib-add-rpath -fveclib=ArmPL %s 2>&1 | FileCheck --check-prefix=CHECK-RPATH-ARMPL %s
+// CHECK-RPATH-ARMPL: "--push-state" "--as-needed" "-lm" "-lamath" "-lm" "--pop-state"
+// CHECK-RPATH-ARMPL-SAME: "-rpath"

flang/test/Driver/fveclib.f90

@@ -30,3 +30,20 @@
 
 ! TODO: if we add support for -nostdlib or -nodefaultlibs we need to test that
 ! these prevent "-framework Accelerate" being added on Darwin
+
+! RUN: %flang -### --target=aarch64-pc-windows-msvc -fveclib=ArmPL %s 2>&1 | FileCheck --check-prefix=CHECK-LINKING-ARMPL-MSVC %s
+! RUN: %flang -### --target=aarch64-linux-gnu -fveclib=ArmPL %s 2>&1 | FileCheck --check-prefix=CHECK-LINKING-ARMPL-LINUX %s
+! RUN: %flang -### --target=aarch64-linux-gnu -fveclib=ArmPL %s -lamath 2>&1 | FileCheck --check-prefix=CHECK-LINKING-AMATH-BEFORE-ARMPL-LINUX %s
+! RUN: %flang -### --target=arm64-apple-darwin -fveclib=ArmPL %s 2>&1 | FileCheck --check-prefix=CHECK-LINKING-ARMPL-DARWIN %s
+! RUN: %flang -### --target=arm64-apple-darwin -fveclib=ArmPL %s -lamath 2>&1 | FileCheck --check-prefix=CHECK-LINKING-AMATH-BEFORE-ARMPL-DARWIN %s
+! CHECK-LINKING-ARMPL-LINUX: "--push-state" "--as-needed" "-lm" "-lamath" "-lm" "--pop-state"
+! CHECK-LINKING-ARMPL-DARWIN: "-lm" "-lamath" "-lm"
+! CHECK-LINKING-ARMPL-MSVC: "--dependent-lib=amath"
+! CHECK-LINKING-AMATH-BEFORE-ARMPL-LINUX: "-lamath" {{.*}}"--push-state" "--as-needed" "-lm" "-lamath" "-lm" "--pop-state"
+! CHECK-LINKING-AMATH-BEFORE-ARMPL-DARWIN: "-lamath" {{.*}}"-lm" "-lamath" "-lm"
+
+! RUN: %flang -### --target=aarch64-linux-gnu -resource-dir=%S/../../../clang/test/Driver/Inputs/resource_dir_with_arch_subdir -frtlib-add-rpath -fveclib=ArmPL %s 2>&1 | FileCheck --check-prefix=CHECK-RPATH-ARMPL %s
+! CHECK-RPATH-ARMPL: "--push-state" "--as-needed" "-lm" "-lamath" "-lm" "--pop-state"
+! We need to see "-rpath" at least twice, one for veclib, one for the Fortran runtime
+! CHECK-RPATH-ARMPL-SAME: "-rpath"
+! CHECK-RPATH-ARMPL-SAME: "-rpath"