[clang] [Clang][Hexagon] Use --cstdlib flag to choose Picolibc (PR #183257)

[via cfe-commits]

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@@ -596,25 +614,23 @@ void HexagonToolChain::getHexagonLibraryPaths(const ArgList &Args,
   std::copy(D.PrefixDirs.begin(), D.PrefixDirs.end(),
             std::back_inserter(RootDirs));
 
-  std::string SysRoot(getEffectiveSysRoot());
+  std::string SysRoot(getEffectiveSysRoot(Args));
   if (!llvm::is_contained(RootDirs, SysRoot))
     RootDirs.push_back(SysRoot);
 
   bool HasPIC = Args.hasArg(options::OPT_fpic, options::OPT_fPIC);
-  // Assume G0 with -shared.
-  bool HasG0 = Args.hasArg(options::OPT_shared);
+  bool HasG0 = false;
   if (auto G = getSmallDataThreshold(Args))
     HasG0 = *G == 0;
 
   const std::string CpuVer = GetTargetCPUVersion(Args).str();
   for (auto &Dir : RootDirs) {
     std::string LibDir = Dir + "/lib";
     std::string LibDirCpu = LibDir + '/' + CpuVer;
-    if (HasG0) {
-      if (HasPIC)
-        LibPaths.push_back(LibDirCpu + "/G0/pic");
+    if (HasPIC)
+      LibPaths.push_back(LibDirCpu + "/G0/pic");
+    if (HasG0)
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quic-k wrote:

-fPIC is always G0, right? @quic-akaryaki 
also, can we add -L/..../lib/<cpu>/G0 after -L/..../lib/<cpu> for non-G0 code, so if we don't have non-G0 version of some libs, we can fall back to G0 libs

my understanding of small data libs is, small-data(G8) libraries won’t work with non-small data(G0) objects, but non-small-data(G0) libraries will work with small data(G8) objects


https://github.com/llvm/llvm-project/pull/183257