[PATCH] D126299: [Driver] Support linking to compiler-rt for target AVR

[Ben Shi via Phabricator via cfe-commits]

benshi001 added inline comments.


================
Comment at: clang/lib/Driver/ToolChains/AVR.cpp:463
+std::string
+AVRToolChain::buildCompilerRTBasename(const llvm::opt::ArgList &Args,
+                                      StringRef Component, FileType Type,
----------------
This method decides the file name of compiler-rt, it is expected to be

libclang_rt.builtins-avrfamily.a, such as

libclang_rt.builtins-avr51.a
libclang_rt.builtins-avrtiny.a
libclang_rt.builtins-avrxmega3.a


================
Comment at: clang/lib/Driver/ToolChains/AVR.cpp:482
+
+std::string AVRToolChain::getCompilerRTPath() const {
+  // Return default path appended with "/avr", if it exists.
----------------
This method decides the library path of compiler-rt, it is
`$(RESOURCE_DIR)/lib/avr` or `$(RESOURCE_DIR)/lib/`. The resource dir is either explicitly specified via user option `-resource-dir` or has default value `$(LLVM_INSTALL_DIR)/lib/clang/$(LLVM_VERSION)`. such as

```
/opt/avr-tool-chain/lib/clang/14.0.1/lib/avr
/opt/avr-tool-chain/lib/clang/14.0.1/lib/
```


================
Comment at: clang/lib/Driver/ToolChains/AVR.cpp:492
+
+ToolChain::RuntimeLibType AVRToolChain::GetDefaultRuntimeLibType() const {
+  return GCCInstallation.isValid() ? ToolChain::RLT_Libgcc
----------------
Currently we still use libgcc if --rtlib option is not specified.


================
Comment at: clang/lib/Driver/ToolChains/AVR.cpp:541
+  assert(
+      (RtLib == ToolChain::RLT_Libgcc || RtLib == ToolChain::RLT_CompilerRT) &&
+      "unknown runtime library");
----------------
Currently we only allow --rtlib=libgcc and --rtlib=compiler-rt


================
Comment at: clang/lib/Driver/ToolChains/AVR.cpp:564
+        if (RtLib == ToolChain::RLT_Libgcc)
+          CmdArgs.push_back(Args.MakeArgString("-L" + TC.getGCCInstallPath() +
+                                               "/" + SubPath));
----------------
If --rtlib is not specified or specified to libgcc, then we generate -L$PATH_TO_LIBGCC


================
Comment at: clang/lib/Driver/ToolChains/AVR.cpp:595
+    // Link to libgcc.
+    if (RtLib == ToolChain::RLT_Libgcc)
+      CmdArgs.push_back("-lgcc");
----------------
If --rtlib is not specified or specified to libgcc, then we generate -lgcc


================
Comment at: clang/lib/Driver/ToolChains/AVR.cpp:608
+    // Link to compiler-rt.
+    if (RtLib == ToolChain::RLT_CompilerRT) {
+      std::string RtLib =
----------------
If --rtlib=compiler-rt is explicitly specified, we directly put the libclang.builtins-avrxxx.a as input file, other than -lclang.builtins-avrxxx, this is a tradition from other platforms, such as x86 and arm.


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  https://reviews.llvm.org/D126299/new/

https://reviews.llvm.org/D126299