[clang] [clang][driver] Add avr-libc's default linker script to lld (PR #68507)

[Ben Shi via cfe-commits]

https://github.com/benshi001 created https://github.com/llvm/llvm-project/pull/68507

If `-fuse-ld=lld` is specified but no user linker script is offered, we try to use avr-libc's default one for lld. (not needed for GNU ld)

>From 2ac033cc4750ffda8f1aded4b896de93713047ad Mon Sep 17 00:00:00 2001
From: Ben Shi <bennshi at tencent.com>
Date: Sun, 8 Oct 2023 15:00:32 +0800
Subject: [PATCH] [clang][driver] Add avr-libc's default linker script to lld

If `-fuse-ld=lld` is specified but no user linker script is offered,
we try to use avr-libc's default one for lld. (not needed for GNU ld)
---
 clang/lib/Driver/ToolChains/AVR.cpp           | 14 +++++++++++--
 .../usr/lib/avr/lib/ldscripts/avrtiny.x       |  0
 .../usr/lib/avr/lib/ldscripts/avrxmega6.x     |  0
 clang/test/Driver/avr-ld.c                    | 21 +++++++++++++++++++
 4 files changed, 33 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/Driver/Inputs/basic_avr_tree/usr/lib/avr/lib/ldscripts/avrtiny.x
 create mode 100644 clang/test/Driver/Inputs/basic_avr_tree/usr/lib/avr/lib/ldscripts/avrxmega6.x

diff --git a/clang/lib/Driver/ToolChains/AVR.cpp b/clang/lib/Driver/ToolChains/AVR.cpp
index 81f501d417345d1..9b15b22ecb2218a 100644
--- a/clang/lib/Driver/ToolChains/AVR.cpp
+++ b/clang/lib/Driver/ToolChains/AVR.cpp
@@ -549,8 +549,18 @@ void AVR::Linker::ConstructJob(Compilation &C, const JobAction &JA,
 
     CmdArgs.push_back("--end-group");
 
-    // Add user specified linker script.
-    Args.AddAllArgs(CmdArgs, options::OPT_T);
+    // Add avr-libc's linker script to lld by default, if it exists.
+    if (!Args.hasArg(options::OPT_T) &&
+        Linker.find("lld") != std::string::npos) {
+      std::string Path(*AVRLibcRoot + "/lib/ldscripts/");
+      Path += *FamilyName;
+      Path += ".x";
+      if (llvm::sys::fs::exists(Path))
+        CmdArgs.push_back(Args.MakeArgString("-T" + Path));
+    }
+    // Otherwise add user specified linker script to either avr-ld or lld.
+    else
+      Args.AddAllArgs(CmdArgs, options::OPT_T);
 
     if (Args.hasFlag(options::OPT_mrelax, options::OPT_mno_relax, true))
       CmdArgs.push_back("--relax");
diff --git a/clang/test/Driver/Inputs/basic_avr_tree/usr/lib/avr/lib/ldscripts/avrtiny.x b/clang/test/Driver/Inputs/basic_avr_tree/usr/lib/avr/lib/ldscripts/avrtiny.x
new file mode 100644
index 000000000000000..e69de29bb2d1d64
diff --git a/clang/test/Driver/Inputs/basic_avr_tree/usr/lib/avr/lib/ldscripts/avrxmega6.x b/clang/test/Driver/Inputs/basic_avr_tree/usr/lib/avr/lib/ldscripts/avrxmega6.x
new file mode 100644
index 000000000000000..e69de29bb2d1d64
diff --git a/clang/test/Driver/avr-ld.c b/clang/test/Driver/avr-ld.c
index 4042ecb89adf5f1..769eb8763caaf61 100644
--- a/clang/test/Driver/avr-ld.c
+++ b/clang/test/Driver/avr-ld.c
@@ -57,3 +57,24 @@
 // RUN: %clang -### --target=avr -mmcu=atmega328 -fuse-ld=lld -flto --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKS %s
 // LINKS: {{".*ld.*"}} {{.*}} "--defsym=__DATA_REGION_ORIGIN__=0x800100" "-plugin-opt=mcpu=atmega328"
 // LINKS-NOT: "-plugin-opt=thinlto"
+
+// RUN: %clang -### --target=avr -mmcu=attiny40 -fuse-ld=lld --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKT0 %s
+// LINKT0: {{".*lld.*"}} {{.*}} {{"-T.*avrtiny.x"}}
+// LINKT0-NOT: "-mavrtiny"
+
+// RUN: %clang -### --target=avr -mmcu=atxmega384c3 -fuse-ld=lld --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKT1 %s
+// LINKT1: {{".*lld.*"}} {{.*}} {{"-T.*avrxmega6.x"}}
+// LINKT1-NOT: "-mavrxmega6"
+
+// RUN: %clang -### --target=avr -mmcu=atmega328 -fuse-ld=lld --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKT2 %s
+// LINKT2: {{".*lld.*"}}
+// LINKT2-NOT: {{"-T.*"}}
+
+// RUN: %clang -### --target=avr -mmcu=attiny40 --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKT3 %s
+// LINKT3: {{".*ld.*"}} {{.*}} "-mavrtiny"
+// LINKT3-NOT: {{"-T.*"}}
+
+// RUN: %clang -### --target=avr -mmcu=attiny40 --sysroot %S/Inputs/basic_avr_tree -fuse-ld=lld -T %S/Inputs/basic_avr_tree/usr/lib/avr/lib/ldscripts/avrxmega6.x %s 2>&1 | FileCheck -check-prefix LINKT4 %s
+// LINKT4: {{".*lld.*"}} {{.*}} {{"-T.*avrxmega6.x"}}
+// LINKT4-NOT: {{"-T.*avrtiny.x"}}
+// LINKT4-NOT: "-mavrtiny"