[RISCV] Improve sysroot computation if no GCC install detected

If a GCC installed is not detected, the driver would default to
the root of the filesystem. This is not ideal when this doesn't
match the install directory of the toolchain and can cause
undesireable behavior such as picking up system libraries or
the system linker when cross-compiling.

Differential Revision: https://reviews.llvm.org/D68391

Author: edward-jones

clang/lib/Driver/ToolChains/RISCVToolchain.cpp

@@ -33,6 +33,8 @@ RISCVToolChain::RISCVToolChain(const Driver &D, const llvm::Triple &Triple,
     getFilePaths().push_back(GCCInstallation.getInstallPath().str());
     getProgramPaths().push_back(
         (GCCInstallation.getParentLibPath() + "/../bin").str());
+  } else {
+    getProgramPaths().push_back(D.Dir);
   }
 }
 
@@ -74,17 +76,22 @@ std::string RISCVToolChain::computeSysRoot() const {
   if (!getDriver().SysRoot.empty())
     return getDriver().SysRoot;
 
-  if (!GCCInstallation.isValid())
-    return std::string();
-
-  StringRef LibDir = GCCInstallation.getParentLibPath();
-  StringRef TripleStr = GCCInstallation.getTriple().str();
-  std::string SysRootDir = LibDir.str() + "/../" + TripleStr.str();
+  SmallString<128> SysRootDir;
+  if (GCCInstallation.isValid()) {
+    StringRef LibDir = GCCInstallation.getParentLibPath();
+    StringRef TripleStr = GCCInstallation.getTriple().str();
+    llvm::sys::path::append(SysRootDir, LibDir, "..", TripleStr);
+  } else {
+    // Use the triple as provided to the driver. Unlike the parsed triple
+    // this has not been normalized to always contain every field.
+    llvm::sys::path::append(SysRootDir, getDriver().Dir, "..",
+                            getDriver().getTargetTriple());
+  }
 
   if (!llvm::sys::fs::exists(SysRootDir))
     return std::string();
 
-  return SysRootDir;
+  return SysRootDir.str();
 }
 
 void RISCV::Linker::ConstructJob(Compilation &C, const JobAction &JA,

clang/test/Driver/Inputs/basic_riscv32_nogcc_tree/bin/riscv32-unknown-elf-ld

@@ -0,0 +1 @@
+#!/bin/true

clang/test/Driver/Inputs/basic_riscv32_nogcc_tree/riscv32-unknown-elf/lib/crt0.o

@@ -0,0 +1 @@
+#!/bin/true

clang/test/Driver/Inputs/basic_riscv32_nogcc_tree/riscv32-unknown-elf/lib/crtbegin.o

@@ -0,0 +1,33 @@
+// A basic clang -cc1 command-line, and simple environment check.
+
+// The tests here are similar to those in riscv32-toolchain.c, however
+// these tests need to create symlinks to test directory trees in order to
+// set up the environment and therefore shell support is required.
+// REQUIRES: shell
+// UNSUPPORTED: system-windows
+
+// If there is no GCC install detected then the driver searches for executables
+// and runtime starting from the directory tree above the driver itself.
+// The test below checks that the driver correctly finds the linker and
+// runtime if and only if they exist.
+//
+// RUN: mkdir -p %T/testroot-riscv32-baremetal-nogcc/bin
+// RUN: [ ! -s %T/testroot-riscv32-baremetal-nogcc/bin/clang ] || rm %T/testroot-riscv32-baremetal-nogcc/bin/clang
+// RUN: [ ! -s %T/testroot-riscv32-baremetal-nogcc/bin/riscv32-unknown-elf-ld ] || rm %T/testroot-riscv32-baremetal-nogcc/bin/riscv32-unknown-elf-ld
+// RUN: [ ! -s %T/testroot-riscv32-baremetal-nogcc/riscv32-unknown-elf ] || rm %T/testroot-riscv32-baremetal-nogcc/riscv32-unknown-elf
+// RUN: ln -s %clang %T/testroot-riscv32-baremetal-nogcc/bin/clang
+// RUN: ln -s %S/Inputs/basic_riscv32_nogcc_tree/bin/riscv32-unknown-elf-ld %T/testroot-riscv32-baremetal-nogcc/bin/riscv32-unknown-elf-ld
+// RUN: ln -s %S/Inputs/basic_riscv32_nogcc_tree/riscv32-unknown-elf %T/testroot-riscv32-baremetal-nogcc/riscv32-unknown-elf
+// RUN: %T/testroot-riscv32-baremetal-nogcc/bin/clang %s -### -no-canonical-prefixes \
+// RUN:    -target riscv32-unknown-elf 2>&1 \
+// RUN:    | FileCheck -check-prefix=C-RV32-BAREMETAL-ILP32-NOGCC %s
+
+// C-RV32-BAREMETAL-ILP32-NOGCC: InstalledDir: [[DRIVERDIR:.*]]
+// C-RV32-BAREMETAL-ILP32-NOGCC: "-fuse-init-array"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "-internal-isystem" "[[DRIVERDIR]]/../riscv32-unknown-elf/include"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "[[DRIVERDIR]]/riscv32-unknown-elf-ld"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "[[DRIVERDIR]]/../riscv32-unknown-elf/lib/crt0.o"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "[[DRIVERDIR]]/../riscv32-unknown-elf/lib/crtbegin.o"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "-L[[DRIVERDIR]]/../riscv32-unknown-elf/lib"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "[[DRIVERDIR]]/../riscv32-unknown-elf/lib/crtend.o"

clang/test/Driver/Inputs/basic_riscv32_nogcc_tree/riscv32-unknown-elf/lib/crtend.o

@@ -0,0 +1,33 @@
+// A basic clang -cc1 command-line, and simple environment check.
+
+// The tests here are similar to those in riscv64-toolchain.c, however
+// these tests need to create symlinks to test directory trees in order to
+// set up the environment and therefore shell support is required.
+// REQUIRES: shell
+// UNSUPPORTED: system-windows
+
+// If there is no GCC install detected then the driver searches for executables
+// and runtime starting from the directory tree above the driver itself.
+// The test below checks that the driver correctly finds the linker and
+// runtime if and only if they exist.
+//
+// RUN: mkdir -p %T/testroot-riscv64-baremetal-nogcc/bin
+// RUN: [ ! -s %T/testroot-riscv64-baremetal-nogcc/bin/clang ] || rm %T/testroot-riscv64-baremetal-nogcc/bin/clang
+// RUN: [ ! -s %T/testroot-riscv64-baremetal-nogcc/bin/riscv64-unknown-elf-ld ] || rm %T/testroot-riscv64-baremetal-nogcc/bin/riscv64-unknown-elf-ld
+// RUN: [ ! -s %T/testroot-riscv64-baremetal-nogcc/riscv64-unknown-elf ] || rm %T/testroot-riscv64-baremetal-nogcc/riscv64-unknown-elf
+// RUN: ln -s %clang %T/testroot-riscv64-baremetal-nogcc/bin/clang
+// RUN: ln -s %S/Inputs/basic_riscv64_nogcc_tree/bin/riscv64-unknown-elf-ld %T/testroot-riscv64-baremetal-nogcc/bin/riscv64-unknown-elf-ld
+// RUN: ln -s %S/Inputs/basic_riscv64_nogcc_tree/riscv64-unknown-elf %T/testroot-riscv64-baremetal-nogcc/riscv64-unknown-elf
+// RUN: %T/testroot-riscv64-baremetal-nogcc/bin/clang %s -### -no-canonical-prefixes \
+// RUN:    -target riscv64-unknown-elf 2>&1 \
+// RUN:    | FileCheck -check-prefix=C-RV64-BAREMETAL-LP64-NOGCC %s
+
+// C-RV64-BAREMETAL-LP64-NOGCC: InstalledDir: [[DRIVERDIR:.*]]
+// C-RV64-BAREMETAL-LP64-NOGCC: "-fuse-init-array"
+// C-RV64-BAREMETAL-LP64-NOGCC: "-internal-isystem" "[[DRIVERDIR]]/../riscv64-unknown-elf/include"
+// C-RV64-BAREMETAL-LP64-NOGCC: "[[DRIVERDIR]]/riscv64-unknown-elf-ld"
+// C-RV64-BAREMETAL-LP64-NOGCC: "[[DRIVERDIR]]/../riscv64-unknown-elf/lib/crt0.o"
+// C-RV64-BAREMETAL-LP64-NOGCC: "[[DRIVERDIR]]/../riscv64-unknown-elf/lib/crtbegin.o"
+// C-RV64-BAREMETAL-LP64-NOGCC: "-L[[DRIVERDIR]]/../riscv64-unknown-elf/lib"
+// C-RV64-BAREMETAL-LP64-NOGCC: "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
+// C-RV64-BAREMETAL-LP64-NOGCC: "[[DRIVERDIR]]/../riscv64-unknown-elf/lib/crtend.o"