[LLVM] [Clang] Support for Gentoo `*t64` triples (64-bit time_t ABIs) (#111302)

Gentoo is planning to introduce a `*t64` suffix for triples that will be
used by 32-bit platforms that use 64-bit `time_t`. Add support for
parsing and accepting these triples, and while at it make clang
automatically enable the necessary glibc feature macros when this suffix
is used.

An open question is whether we can backport this to LLVM 19.x. After
all, adding new triplets to Triple sounds like an ABI change — though I
suppose we can minimize the risk of breaking something if we move new
enum values to the very end.

9 files changed, 36 insertions, 5 deletions

diff --git a/clang/lib/Basic/Targets/ARM.cpp b/clang/lib/Basic/Targets/ARM.cpp
index c56b8d9..c87300b 100644
--- a/clang/lib/Basic/Targets/ARM.cpp
+++ b/clang/lib/Basic/Targets/ARM.cpp
@@ -313,7 +313,9 @@ ARMTargetInfo::ARMTargetInfo(const llvm::Triple &Triple,
     switch (Triple.getEnvironment()) {
     case llvm::Triple::Android:
     case llvm::Triple::GNUEABI:
+    case llvm::Triple::GNUEABIT64:
     case llvm::Triple::GNUEABIHF:
+    case llvm::Triple::GNUEABIHFT64:
     case llvm::Triple::MuslEABI:
     case llvm::Triple::MuslEABIHF:
     case llvm::Triple::OpenHOS:
diff --git a/clang/lib/Basic/Targets/OSTargets.h b/clang/lib/Basic/Targets/OSTargets.h
index a83d646..75f53e9 100644
--- a/clang/lib/Basic/Targets/OSTargets.h
+++ b/clang/lib/Basic/Targets/OSTargets.h
@@ -337,6 +337,10 @@ protected:
       Builder.defineMacro("_GNU_SOURCE");
     if (this->HasFloat128)
       Builder.defineMacro("__FLOAT128__");
+    if (Triple.isTime64ABI()) {
+      Builder.defineMacro("_FILE_OFFSET_BITS", "64");
+      Builder.defineMacro("_TIME_BITS", "64");
+    }
   }
 
 public:
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 7a7dea4..7f0e0de 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -175,10 +175,7 @@ createTargetCodeGenInfo(CodeGenModule &CGM) {
     else if (ABIStr == "aapcs16")
       Kind = ARMABIKind::AAPCS16_VFP;
     else if (CodeGenOpts.FloatABI == "hard" ||
-             (CodeGenOpts.FloatABI != "soft" &&
-              (Triple.getEnvironment() == llvm::Triple::GNUEABIHF ||
-               Triple.getEnvironment() == llvm::Triple::MuslEABIHF ||
-               Triple.getEnvironment() == llvm::Triple::EABIHF)))
+             (CodeGenOpts.FloatABI != "soft" && Triple.isHardFloatABI()))
       Kind = ARMABIKind::AAPCS_VFP;
 
     return createARMTargetCodeGenInfo(CGM, Kind);
diff --git a/clang/lib/CodeGen/Targets/ARM.cpp b/clang/lib/CodeGen/Targets/ARM.cpp
index f7d7471..49ac1a7 100644
--- a/clang/lib/CodeGen/Targets/ARM.cpp
+++ b/clang/lib/CodeGen/Targets/ARM.cpp
@@ -35,7 +35,9 @@ public:
     case llvm::Triple::EABI:
     case llvm::Triple::EABIHF:
     case llvm::Triple::GNUEABI:
+    case llvm::Triple::GNUEABIT64:
     case llvm::Triple::GNUEABIHF:
+    case llvm::Triple::GNUEABIHFT64:
     case llvm::Triple::MuslEABI:
     case llvm::Triple::MuslEABIHF:
       return true;
@@ -48,6 +50,7 @@ public:
     switch (getTarget().getTriple().getEnvironment()) {
     case llvm::Triple::EABIHF:
     case llvm::Triple::GNUEABIHF:
+    case llvm::Triple::GNUEABIHFT64:
     case llvm::Triple::MuslEABIHF:
       return true;
     default:
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index ba850cf..9878a9d 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -610,7 +610,8 @@ static llvm::Triple computeTargetTriple(const Driver &D,
     if (A->getOption().matches(options::OPT_m64) ||
         A->getOption().matches(options::OPT_maix64)) {
       AT = Target.get64BitArchVariant().getArch();
-      if (Target.getEnvironment() == llvm::Triple::GNUX32)
+      if (Target.getEnvironment() == llvm::Triple::GNUX32 ||
+          Target.getEnvironment() == llvm::Triple::GNUT64)
         Target.setEnvironment(llvm::Triple::GNU);
       else if (Target.getEnvironment() == llvm::Triple::MuslX32)
         Target.setEnvironment(llvm::Triple::Musl);
@@ -673,6 +674,7 @@ static llvm::Triple computeTargetTriple(const Driver &D,
       } else if (ABIName == "n32") {
         Target = Target.get64BitArchVariant();
         if (Target.getEnvironment() == llvm::Triple::GNU ||
+            Target.getEnvironment() == llvm::Triple::GNUT64 ||
             Target.getEnvironment() == llvm::Triple::GNUABI64)
           Target.setEnvironment(llvm::Triple::GNUABIN32);
         else if (Target.getEnvironment() == llvm::Triple::Musl ||
@@ -681,6 +683,7 @@ static llvm::Triple computeTargetTriple(const Driver &D,
       } else if (ABIName == "64") {
         Target = Target.get64BitArchVariant();
         if (Target.getEnvironment() == llvm::Triple::GNU ||
+            Target.getEnvironment() == llvm::Triple::GNUT64 ||
             Target.getEnvironment() == llvm::Triple::GNUABIN32)
           Target.setEnvironment(llvm::Triple::GNUABI64);
         else if (Target.getEnvironment() == llvm::Triple::Musl ||
diff --git a/clang/lib/Driver/ToolChains/Arch/ARM.cpp b/clang/lib/Driver/ToolChains/Arch/ARM.cpp
index a6041b8..0489911 100644
--- a/clang/lib/Driver/ToolChains/Arch/ARM.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/ARM.cpp
@@ -327,6 +327,11 @@ void arm::setFloatABIInTriple(const Driver &D, const ArgList &Args,
     Triple.setEnvironment(isHardFloat ? llvm::Triple::GNUEABIHF
                                       : llvm::Triple::GNUEABI);
     break;
+  case llvm::Triple::GNUEABIT64:
+  case llvm::Triple::GNUEABIHFT64:
+    Triple.setEnvironment(isHardFloat ? llvm::Triple::GNUEABIHFT64
+                                      : llvm::Triple::GNUEABIT64);
+    break;
   case llvm::Triple::EABI:
   case llvm::Triple::EABIHF:
     Triple.setEnvironment(isHardFloat ? llvm::Triple::EABIHF
@@ -414,10 +419,12 @@ arm::FloatABI arm::getDefaultFloatABI(const llvm::Triple &Triple) {
       return FloatABI::Soft;
     switch (Triple.getEnvironment()) {
     case llvm::Triple::GNUEABIHF:
+    case llvm::Triple::GNUEABIHFT64:
     case llvm::Triple::MuslEABIHF:
     case llvm::Triple::EABIHF:
       return FloatABI::Hard;
     case llvm::Triple::GNUEABI:
+    case llvm::Triple::GNUEABIT64:
     case llvm::Triple::MuslEABI:
     case llvm::Triple::EABI:
       // EABI is always AAPCS, and if it was not marked 'hard', it's softfp
diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp
index 09bb2df..1eacb25 100644
--- a/clang/lib/Driver/ToolChains/Gnu.cpp
+++ b/clang/lib/Driver/ToolChains/Gnu.cpp
@@ -2698,6 +2698,7 @@ void Generic_GCC::GCCInstallationDetector::AddDefaultGCCPrefixes(
   case llvm::Triple::thumb:
     LibDirs.append(begin(ARMLibDirs), end(ARMLibDirs));
     if (TargetTriple.getEnvironment() == llvm::Triple::GNUEABIHF ||
+        TargetTriple.getEnvironment() == llvm::Triple::GNUEABIHFT64 ||
         TargetTriple.getEnvironment() == llvm::Triple::MuslEABIHF ||
         TargetTriple.getEnvironment() == llvm::Triple::EABIHF) {
       TripleAliases.append(begin(ARMHFTriples), end(ARMHFTriples));
@@ -2709,6 +2710,7 @@ void Generic_GCC::GCCInstallationDetector::AddDefaultGCCPrefixes(
   case llvm::Triple::thumbeb:
     LibDirs.append(begin(ARMebLibDirs), end(ARMebLibDirs));
     if (TargetTriple.getEnvironment() == llvm::Triple::GNUEABIHF ||
+        TargetTriple.getEnvironment() == llvm::Triple::GNUEABIHFT64 ||
         TargetTriple.getEnvironment() == llvm::Triple::MuslEABIHF ||
         TargetTriple.getEnvironment() == llvm::Triple::EABIHF) {
       TripleAliases.append(begin(ARMebHFTriples), end(ARMebHFTriples));
diff --git a/clang/lib/Driver/ToolChains/Linux.cpp b/clang/lib/Driver/ToolChains/Linux.cpp
index 59c048c..d1cb625 100644
--- a/clang/lib/Driver/ToolChains/Linux.cpp
+++ b/clang/lib/Driver/ToolChains/Linux.cpp
@@ -511,6 +511,7 @@ std::string Linux::getDynamicLinker(const ArgList &Args) const {
   case llvm::Triple::thumbeb: {
     const bool HF =
         Triple.getEnvironment() == llvm::Triple::GNUEABIHF ||
+        Triple.getEnvironment() == llvm::Triple::GNUEABIHFT64 ||
         tools::arm::getARMFloatABI(*this, Args) == tools::arm::FloatABI::Hard;
 
     LibDir = "lib";
diff --git a/clang/test/Preprocessor/time64.c b/clang/test/Preprocessor/time64.c
new file mode 100644
index 0000000..e9e26e0
--- /dev/null
+++ b/clang/test/Preprocessor/time64.c
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -E -dM -triple=i686-pc-linux-gnu /dev/null | FileCheck -match-full-lines -check-prefix TIME32 %s
+// RUN: %clang_cc1 -E -dM -triple=i686-pc-linux-gnut64 /dev/null | FileCheck -match-full-lines -check-prefix TIME64 %s
+// RUN: %clang_cc1 -E -dM -triple=armv5tel-softfloat-linux-gnueabi /dev/null | FileCheck -match-full-lines -check-prefix TIME32 %s
+// RUN: %clang_cc1 -E -dM -triple=armv5tel-softfloat-linux-gnueabit64 /dev/null | FileCheck -match-full-lines -check-prefix TIME64 %s
+// RUN: %clang_cc1 -E -dM -triple=armv7a-unknown-linux-gnueabihf /dev/null | FileCheck -match-full-lines -check-prefix TIME32 %s
+// RUN: %clang_cc1 -E -dM -triple=armv7a-unknown-linux-gnueabihft64 /dev/null | FileCheck -match-full-lines -check-prefix TIME64 %s
+//
+// TIME32-NOT:#define _FILE_OFFSET_BITS 64
+// TIME32-NOT:#define _TIME_BITS 64
+//
+// TIME64:#define _FILE_OFFSET_BITS 64
+// TIME64:#define _TIME_BITS 64