Revert "[Driver] Drop obsoleted Ubuntu 11.04 gcc detection"

This reverts commit bdf39e6.

The change is failing on Fedora 33 (x86-64).

clang/lib/Driver/ToolChains/Gnu.cpp

@@ -2506,6 +2506,7 @@ void Generic_GCC::GCCInstallationDetector::ScanLibDirForGCCTriple(
     const llvm::Triple &TargetTriple, const ArgList &Args,
     const std::string &LibDir, StringRef CandidateTriple,
     bool NeedsBiarchSuffix, bool GCCDirExists, bool GCCCrossDirExists) {
+  llvm::Triple::ArchType TargetArch = TargetTriple.getArch();
   // Locations relative to the system lib directory where GCC's triple-specific
   // directories might reside.
   struct GCCLibSuffix {
@@ -2529,7 +2530,15 @@ void Generic_GCC::GCCInstallationDetector::ScanLibDirForGCCTriple(
       // files in that location, not just GCC installation data.
       {CandidateTriple.str(), "..",
        TargetTriple.getVendor() == llvm::Triple::Freescale ||
-           TargetTriple.getVendor() == llvm::Triple::OpenEmbedded}};
+       TargetTriple.getVendor() == llvm::Triple::OpenEmbedded},
+
+      // Deal with cases (on Ubuntu) where the system architecture could be i386
+      // but the GCC target architecture could be (say) i686.
+      // FIXME: It may be worthwhile to generalize this and look for a second
+      // triple.
+      {"i386-linux-gnu/gcc/" + CandidateTriple.str(), "../../..",
+       (TargetArch == llvm::Triple::x86 &&
+        TargetTriple.getOS() != llvm::Triple::Solaris)}};
 
   for (auto &Suffix : Suffixes) {
     if (!Suffix.Active)

clang/test/Driver/gcc-toolchain.cpp

@@ -1,31 +1,34 @@
 // Test that gcc-toolchain option is working correctly
 //
 // RUN: %clangxx -no-canonical-prefixes %s -### -o %t 2>&1 \
-// RUN:   --target=x86_64-linux-gnu --gcc-toolchain=%S/Inputs/ubuntu_14.04_multiarch_tree/usr | \
-// RUN:   FileCheck %s
+// RUN:     --target=i386-unknown-linux -stdlib=libstdc++ \
+// RUN:     --gcc-toolchain=%S/Inputs/ubuntu_11.04_multiarch_tree/usr \
+// RUN:     --sysroot="" \
+// RUN:   | FileCheck %s
 //
 // Additionally check that the legacy spelling of the flag works.
 // RUN: %clangxx -no-canonical-prefixes %s -### -o %t 2>&1 \
-// RUN:   --target=x86_64-linux-gnu -gcc-toolchain %S/Inputs/ubuntu_14.04_multiarch_tree/usr | \
-// RUN:   FileCheck %s
+// RUN:     --target=i386-unknown-linux -stdlib=libstdc++ \
+// RUN:     -gcc-toolchain %S/Inputs/ubuntu_11.04_multiarch_tree/usr \
+// RUN:     --sysroot="" \
+// RUN:   | FileCheck %s
 //
 // Test for header search toolchain detection.
 // CHECK: "-internal-isystem"
-// CHECK: "[[TOOLCHAIN:[^"]+]]/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8"
+// CHECK: "[[TOOLCHAIN:[^"]+]]/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5/../../../../../include/c++/4.5"
 // CHECK: "-internal-isystem"
-// CHECK: "[[TOOLCHAIN]]/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/x86_64-linux-gnu/c++/4.8"
+// CHECK: "[[TOOLCHAIN]]/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5/../../../../../include/c++/4.5/i686-linux-gnu"
 // CHECK: "-internal-isystem"
-// CHECK: "[[TOOLCHAIN]]/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/backward"
+// CHECK: "[[TOOLCHAIN]]/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5/../../../../../include/c++/4.5/backward"
 // CHECK: "-internal-isystem" "/usr/local/include"
 //
 // Test for linker toolchain detection. Note that only the '-L' flags will use
 // the same precise formatting of the path as the '-internal-system' flags
 // above, so we just blanket wildcard match the 'crtbegin.o'.
 // CHECK: "{{[^"]*}}ld{{(.exe)?}}"
-// CHECK-SAME: "{{[^"]*}}/usr/lib/gcc/x86_64-linux-gnu/4.8{{/|\\\\}}crtbegin.o"
-// CHECK-SAME: "-L[[TOOLCHAIN]]/usr/lib/gcc/x86_64-linux-gnu/4.8"
-/// On x86_64, there is an extra usr/lib/gcc/x86_64-linux-gnu/4.8/../../../x86_64-linux-gnu but we should not test it.
-// CHECK-SAME: "-L[[TOOLCHAIN]]/usr/lib/gcc/x86_64-linux-gnu/4.8/../../.."
+// CHECK: "{{[^"]*}}/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5{{/|\\\\}}crtbegin.o"
+// CHECK: "-L[[TOOLCHAIN]]/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5"
+// CHECK: "-L[[TOOLCHAIN]]/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5/../../../.."
 
 /// Test we don't detect GCC installation under -B.
 // RUN: %clangxx -no-canonical-prefixes %s -### -o %t 2>&1 \

clang/test/Driver/linux-header-search.cpp

@@ -67,6 +67,23 @@
 // CHECK-BASIC-LIBSTDCXX-LIBCXXV2-SYSROOT: "-internal-isystem" "[[SYSROOT]]/usr/include/c++/v2"
 // CHECK-BASIC-LIBSTDCXX-LIBCXXV2-SYSROOT: "-internal-isystem" "[[SYSROOT]]/usr/local/include"
 //
+// Test a very broken version of multiarch that shipped in Ubuntu 11.04.
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
+// RUN:     -target i386-unknown-linux -stdlib=libstdc++ \
+// RUN:     --sysroot=%S/Inputs/ubuntu_11.04_multiarch_tree \
+// RUN:     --gcc-toolchain="" \
+// RUN:   | FileCheck --check-prefix=CHECK-UBUNTU-11-04 %s
+// CHECK-UBUNTU-11-04: "{{.*}}clang{{.*}}" "-cc1"
+// CHECK-UBUNTU-11-04: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
+// CHECK-UBUNTU-11-04: "-isysroot" "[[SYSROOT:[^"]+]]"
+// CHECK-UBUNTU-11-04: "-internal-isystem" "[[SYSROOT]]/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5/../../../../../include/c++/4.5"
+// CHECK-UBUNTU-11-04: "-internal-isystem" "[[SYSROOT]]/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5/../../../../../include/c++/4.5/i686-linux-gnu"
+// CHECK-UBUNTU-11-04: "-internal-isystem" "[[SYSROOT]]/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5/../../../../../include/c++/4.5/backward"
+// CHECK-UBUNTU-11-04: "-internal-isystem" "[[SYSROOT]]/usr/local/include"
+// CHECK-UBUNTU-11-04: "-internal-isystem" "[[RESOURCE_DIR]]{{/|\\\\}}include"
+// CHECK-UBUNTU-11-04: "-internal-externc-isystem" "[[SYSROOT]]/include"
+// CHECK-UBUNTU-11-04: "-internal-externc-isystem" "[[SYSROOT]]/usr/include"
+//
 // RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
 // RUN:     -target x86_64-unknown-linux-gnu -stdlib=libstdc++ \
 // RUN:     --sysroot=%S/Inputs/ubuntu_13.04_multiarch_tree \

clang/test/Driver/linux-ld.c

@@ -565,6 +565,21 @@
 // CHECK-BASIC-LIBCXX-C-LINK: "--sysroot=[[SYSROOT]]"
 // CHECK-BASIC-LIBCXX-C-LINK: "-L[[SYSROOT]]/usr/bin/../lib"
 //
+// Test a very broken version of multiarch that shipped in Ubuntu 11.04.
+// RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
+// RUN:     --target=i386-unknown-linux -rtlib=platform \
+// RUN:     --gcc-toolchain="" \
+// RUN:     --sysroot=%S/Inputs/ubuntu_11.04_multiarch_tree \
+// RUN:   | FileCheck --check-prefix=CHECK-UBUNTU-11-04 %s
+// CHECK-UBUNTU-11-04: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
+// CHECK-UBUNTU-11-04: "{{.*}}/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5{{/|\\\\}}crtbegin.o"
+// CHECK-UBUNTU-11-04: "-L[[SYSROOT]]/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5"
+// CHECK-UBUNTU-11-04: "-L[[SYSROOT]]/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5/../../../../i386-linux-gnu"
+// CHECK-UBUNTU-11-04: "-L[[SYSROOT]]/usr/lib/i386-linux-gnu"
+// CHECK-UBUNTU-11-04: "-L[[SYSROOT]]/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5/../../../.."
+// CHECK-UBUNTU-11-04: "-L[[SYSROOT]]/lib"
+// CHECK-UBUNTU-11-04: "-L[[SYSROOT]]/usr/lib"
+//
 // Check multi arch support on Ubuntu 12.04 LTS.
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     --target=arm-unknown-linux-gnueabihf -rtlib=platform \