[Driver] Unify InstalledDir and Dir (#80527)

`Driver::ClangExecutable` is derived from:

* (-canonical-prefixes default): `realpath` on the executable path
* (-no-canonical-prefixes) argv[0] (consult PATH if argv[0] is a word)

`Dir` and `ResourceDir` are derived from `ClangExecutable`. Both
variables are used to derive certain include and library paths.

`InstalledDir` is a related concept used to derive certain other paths.
`InstalledDir` is weird in the -canonical-prefixes mode: Clang
calls `make_absolute` but does not follow symlinks
(FIXME from 9ade6a9).
This causes some search and library paths to be mix-and-matched.

The "Do a PATH lookup, if there are no directory components." logic
makes things worse.
`InstalledDir` is different when you invoke it via `PATH`:
```
% which clang
/usr/bin/clang
% clang -v |& grep InstalledDir
InstalledDir: /usr/bin
% /usr/lib/llvm-16/bin/clang -v |& grep InstalledDir
InstalledDir: /usr/lib/llvm-16/bin
```

I believe `InstalledDir` was a partial solution to
`-no-canonical-prefixes` and should be eventually removed.

This patch removes `SetInstallDir` and relies on Driver::Driver to set
`InstalledDir` to `Dir`. The behavior for regular file `clang` or
`-no-canonical-prefixes` is unchanged.

If a user creates a symlink to the regular file `clang` and uses the
default `-canonical-prefixes`, they now consistently get search and
library paths relative to the regular file `clang`, not mix-and-match
paths.

If a user creates a symlink to the regular file `clang` and replaces
some directorys from the actual installation, they should change the
symlink to a wrapper that calls the underlying clang with
`-no-canonical-prefixes`.

Author: MaskRay

clang/include/clang/Driver/Driver.h

@@ -160,7 +160,7 @@ class Driver {
   /// Target and driver mode components extracted from clang executable name.
   ParsedClangName ClangNameParts;
 
-  /// The path to the installed clang directory, if any.
+  /// TODO: Remove this in favor of Dir.
   std::string InstalledDir;
 
   /// The path to the compiler resource directory.
@@ -433,7 +433,6 @@ class Driver {
       return InstalledDir.c_str();
     return Dir.c_str();
   }
-  void setInstalledDir(StringRef Value) { InstalledDir = std::string(Value); }
 
   bool isSaveTempsEnabled() const { return SaveTemps != SaveTempsNone; }
   bool isSaveTempsObj() const { return SaveTemps == SaveTempsObj; }

clang/test/Driver/darwin-header-search-libcxx.cpp

@@ -193,7 +193,7 @@
 // RUN: ln -sf %t/install/bin/clang %t/symlinked1/bin/clang
 // RUN: mkdir -p %t/symlinked1/include/c++/v1
 
-// RUN: %t/symlinked1/bin/clang -### %s -fsyntax-only 2>&1 \
+// RUN: %t/symlinked1/bin/clang -### %s -no-canonical-prefixes -fsyntax-only 2>&1 \
 // RUN:     --target=x86_64-apple-darwin \
 // RUN:     -stdlib=libc++ \
 // RUN:     -isysroot %S/Inputs/basic_darwin_sdk_usr_cxx_v1 \

clang/test/Driver/mingw-sysroot.cpp

@@ -50,10 +50,12 @@
 // CHECK_TESTROOT_GCC_EXPLICIT: "-internal-isystem" "{{[^"]+}}/testroot-gcc{{/|\\\\}}include"
 
 
-// If there's a matching sysroot next to the clang binary itself, prefer that
+// If -no-canonical-prefixes and there's a matching sysroot next to the clang binary itself, prefer that
 // over a gcc in the path:
 
-// RUN: env "PATH=%T/testroot-gcc/bin:%PATH%" %T/testroot-clang/bin/x86_64-w64-mingw32-clang -target x86_64-w64-mingw32 -rtlib=compiler-rt -stdlib=libstdc++ --sysroot="" -c -### %s 2>&1 | FileCheck -check-prefix=CHECK_TESTROOT_CLANG %s
+// RUN: env "PATH=%T/testroot-gcc/bin:%PATH%" %T/testroot-clang/bin/x86_64-w64-mingw32-clang --target=x86_64-w64-mingw32 -rtlib=compiler-rt -stdlib=libstdc++ --sysroot="" -c -### %s 2>&1 | FileCheck -check-prefix=CHECK_TESTROOT_GCC2 %s
+// RUN: env "PATH=%T/testroot-gcc/bin:%PATH%" %T/testroot-clang/bin/x86_64-w64-mingw32-clang --target=x86_64-w64-mingw32 -rtlib=compiler-rt -stdlib=libstdc++ --sysroot="" -c -### %s -no-canonical-prefixes 2>&1 | FileCheck -check-prefix=CHECK_TESTROOT_CLANG %s
+// CHECK_TESTROOT_GCC2: "{{[^"]+}}/testroot-gcc{{/|\\\\}}x86_64-w64-mingw32{{/|\\\\}}include"
 // CHECK_TESTROOT_CLANG: "{{[^"]+}}/testroot-clang{{/|\\\\}}x86_64-w64-mingw32{{/|\\\\}}include"
 
 
@@ -82,7 +84,7 @@
 // that indicates that we did choose the right base, even if this particular directory
 // actually doesn't exist here.
 
-// RUN: env "PATH=%T/testroot-gcc/bin:%PATH%" %T/testroot-clang-native/bin/clang -target x86_64-w64-mingw32 -rtlib=compiler-rt -stdlib=libstdc++ --sysroot="" -c -### %s 2>&1 | FileCheck -check-prefix=CHECK_TESTROOT_CLANG_NATIVE %s
+// RUN: env "PATH=%T/testroot-gcc/bin:%PATH%" %T/testroot-clang-native/bin/clang -no-canonical-prefixes --target=x86_64-w64-mingw32 -rtlib=compiler-rt -stdlib=libstdc++ --sysroot="" -c -### %s 2>&1 | FileCheck -check-prefix=CHECK_TESTROOT_CLANG_NATIVE %s
 // CHECK_TESTROOT_CLANG_NATIVE: "{{[^"]+}}/testroot-clang-native{{/|\\\\}}x86_64-w64-mingw32{{/|\\\\}}include"
 
 
@@ -93,12 +95,12 @@
 // that defaults to x86_64 mingw, but it's easier to test this in cross setups
 // with symlinks, like the other tests here.)
 
-// RUN: env "PATH=%T/testroot-gcc/bin:%PATH%" %T/testroot-clang/bin/x86_64-w64-mingw32-clang --target=x86_64-w64-mingw32 -m32 -rtlib=compiler-rt -stdlib=libstdc++ --sysroot="" -c -### %s 2>&1 | FileCheck -check-prefix=CHECK_TESTROOT_CLANG_I686 %s
+// RUN: env "PATH=%T/testroot-gcc/bin:%PATH%" %T/testroot-clang/bin/x86_64-w64-mingw32-clang -no-canonical-prefixes --target=x86_64-w64-mingw32 -m32 -rtlib=compiler-rt -stdlib=libstdc++ --sysroot="" -c -### %s 2>&1 | FileCheck -check-prefix=CHECK_TESTROOT_CLANG_I686 %s
 // CHECK_TESTROOT_CLANG_I686: "{{[^"]+}}/testroot-clang{{/|\\\\}}i686-w64-mingw32{{/|\\\\}}include"
 
 
 // If the user calls clang with a custom literal triple, make sure this maps
 // to sysroots with the matching spelling.
 
-// RUN: %T/testroot-custom-triple/bin/clang --target=x86_64-w64-mingw32foo -rtlib=compiler-rt -stdlib=libstdc++ --sysroot="" -c -### %s 2>&1 | FileCheck -check-prefix=CHECK_TESTROOT_CUSTOM_TRIPLE %s
+// RUN: %T/testroot-custom-triple/bin/clang -no-canonical-prefixes --target=x86_64-w64-mingw32foo -rtlib=compiler-rt -stdlib=libstdc++ --sysroot="" -c -### %s 2>&1 | FileCheck -check-prefix=CHECK_TESTROOT_CUSTOM_TRIPLE %s
 // CHECK_TESTROOT_CUSTOM_TRIPLE: "{{[^"]+}}/testroot-custom-triple{{/|\\\\}}x86_64-w64-mingw32foo{{/|\\\\}}include"

clang/test/Driver/no-canonical-prefixes.c

@@ -26,7 +26,7 @@
 // RUN:     | FileCheck --check-prefix=NON-CANONICAL %s
 //
 // FIXME: This should really be '.real'.
-// CANONICAL: InstalledDir: {{.*}}.fake
+// CANONICAL: InstalledDir: {{.*}}bin
 // CANONICAL: {{[/|\\]*}}clang{{.*}}" -cc1
 //
 // NON-CANONICAL: InstalledDir: .{{$}}

clang/test/Driver/program-path-priority.c

@@ -36,7 +36,7 @@
 // RUN: touch %t/notreal-none-elf-gcc && chmod +x %t/notreal-none-elf-gcc
 // RUN: env "PATH=" %t/clang -### -target notreal-none-elf %s 2>&1 | \
 // RUN:   FileCheck --check-prefix=PROG_PATH_NOTREAL_GCC %s
-// PROG_PATH_NOTREAL_GCC: notreal-none-elf-gcc"
+// PROG_PATH_NOTREAL_GCC: notreal-none-unknown-elf
 
 /// <triple>-gcc on the PATH is found
 // RUN: mkdir -p %t/env
@@ -57,7 +57,7 @@
 // RUN: touch %t/gcc && chmod +x %t/gcc
 // RUN: env "PATH=" %t/clang -### -target notreal-none-elf %s 2>&1 | \
 // RUN:   FileCheck --check-prefix=NOTREAL_GCC_PREFERRED %s
-// NOTREAL_GCC_PREFERRED: notreal-none-elf-gcc"
+// NOTREAL_GCC_PREFERRED: notreal-none-unknown-elf"
 // NOTREAL_GCC_PREFERRED-NOT: /gcc"
 
 /// <triple>-gcc on the PATH is preferred to gcc in program path
@@ -125,6 +125,9 @@
 /// Only if there is nothing in the prefix will we search other paths
 /// -f in case $DEFAULT_TRIPLE == %target_triple
 // RUN: rm -f %t/prefix/$DEFAULT_TRIPLE-gcc %t/prefix/%target_triple-gcc %t/prefix/gcc
-// RUN: env "PATH=" %t/clang -### -target notreal-none-elf %s -B %t/prefix 2>&1 | \
-// RUN:   FileCheck --check-prefix=EMPTY_PREFIX_DIR %s
-// EMPTY_PREFIX_DIR: notreal-none-elf-gcc"
+// RUN: env "PATH=" %t/clang -### -canonical-prefixes --target=notreal-none-elf %s -B %t/prefix 2>&1 | \
+// RUN:   FileCheck --check-prefix=EMPTY_PREFIX_DIR1 %s
+// EMPTY_PREFIX_DIR1: gcc"
+// RUN: env "PATH=" %t/clang -### -no-canonical-prefixes --target=notreal-none-elf %s -B %t/prefix 2>&1 | \
+// RUN:   FileCheck --check-prefix=EMPTY_PREFIX_DIR2 %s
+// EMPTY_PREFIX_DIR2: notreal-none-elf-gcc"

clang/test/Driver/rocm-detect.hip

@@ -102,7 +102,7 @@
 // RUN: rm -rf %t/rocm-spack
 // RUN: cp -r %S/Inputs/rocm-spack %t
 // RUN: ln -fs %clang %t/rocm-spack/llvm-amdgpu-4.0.0-ieagcs7inf7runpyfvepqkurasoglq4z/bin/clang
-// RUN: %t/rocm-spack/llvm-amdgpu-4.0.0-ieagcs7inf7runpyfvepqkurasoglq4z/bin/clang -### -v \
+// RUN: %t/rocm-spack/llvm-amdgpu-4.0.0-ieagcs7inf7runpyfvepqkurasoglq4z/bin/clang -### -no-canonical-prefixes -v \
 // RUN:   -resource-dir=%t/rocm-spack/llvm-amdgpu-4.0.0-ieagcs7inf7runpyfvepqkurasoglq4z/lib/clang \
 // RUN:   -target x86_64-linux-gnu --cuda-gpu-arch=gfx900 --print-rocm-search-dirs %s 2>&1 \
 // RUN:   | FileCheck -check-prefixes=SPACK %s
@@ -111,7 +111,7 @@
 // ROCm release. --hip-path and --rocm-device-lib-path can be used to specify them.
 
 // RUN: cp -r %t/rocm-spack/hip-* %t/rocm-spack/hip-4.0.0-abcd
-// RUN: %t/rocm-spack/llvm-amdgpu-4.0.0-ieagcs7inf7runpyfvepqkurasoglq4z/bin/clang -### -v \
+// RUN: %t/rocm-spack/llvm-amdgpu-4.0.0-ieagcs7inf7runpyfvepqkurasoglq4z/bin/clang -### -no-canonical-prefixes -v \
 // RUN:   -target x86_64-linux-gnu --cuda-gpu-arch=gfx900 \
 // RUN:   --hip-path=%t/rocm-spack/hip-4.0.0-abcd \
 // RUN:    %s 2>&1 | FileCheck -check-prefixes=SPACK-SET %s

clang/tools/driver/driver.cpp

@@ -323,28 +323,6 @@ static void FixupDiagPrefixExeName(TextDiagnosticPrinter *DiagClient,
   DiagClient->setPrefix(std::string(ExeBasename));
 }
 
-static void SetInstallDir(SmallVectorImpl<const char *> &argv,
-                          Driver &TheDriver, bool CanonicalPrefixes) {
-  // Attempt to find the original path used to invoke the driver, to determine
-  // the installed path. We do this manually, because we want to support that
-  // path being a symlink.
-  SmallString<128> InstalledPath(argv[0]);
-
-  // Do a PATH lookup, if there are no directory components.
-  if (llvm::sys::path::filename(InstalledPath) == InstalledPath)
-    if (llvm::ErrorOr<std::string> Tmp = llvm::sys::findProgramByName(
-            llvm::sys::path::filename(InstalledPath.str())))
-      InstalledPath = *Tmp;
-
-  // FIXME: We don't actually canonicalize this, we just make it absolute.
-  if (CanonicalPrefixes)
-    llvm::sys::fs::make_absolute(InstalledPath);
-
-  StringRef InstalledPathParent(llvm::sys::path::parent_path(InstalledPath));
-  if (llvm::sys::fs::exists(InstalledPathParent))
-    TheDriver.setInstalledDir(InstalledPathParent);
-}
-
 static int ExecuteCC1Tool(SmallVectorImpl<const char *> &ArgV,
                           const llvm::ToolContext &ToolContext) {
   // If we call the cc1 tool from the clangDriver library (through
@@ -484,7 +462,6 @@ int clang_main(int Argc, char **Argv, const llvm::ToolContext &ToolContext) {
   ProcessWarningOptions(Diags, *DiagOpts, /*ReportDiags=*/false);
 
   Driver TheDriver(Path, llvm::sys::getDefaultTargetTriple(), Diags);
-  SetInstallDir(Args, TheDriver, CanonicalPrefixes);
   auto TargetAndMode = ToolChain::getTargetAndModeFromProgramName(ProgName);
   TheDriver.setTargetAndMode(TargetAndMode);
   // If -canonical-prefixes is set, GetExecutablePath will have resolved Path