MIPS: allow o32 abi with 64bit CPU and 64 abi with 32bit triple

In general, MIPS support ELF format like
   ELF 32-bit LSB relocatable, MIPS, MIPS64 rel2 version 1 (SYSV)
and Linux's VDSO uses it.

Currently clang stop CMDs like
    clang -march=mips64r2 -mabi=32

While it is not needed now, since the the backend support the combination now.

This patch also allows something like
     clang --target=mipsel-linux-gnu -mabi=64
Since the triple can convert to right 64bit one automaticly.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D146269

clang/lib/Basic/Targets/Mips.cpp

@@ -238,37 +238,13 @@ bool MipsTargetInfo::validateTarget(DiagnosticsEngine &Diags) const {
     Diags.Report(diag::err_target_unsupported_cpu_for_micromips) << CPU;
     return false;
   }
-  // FIXME: It's valid to use O32 on a 64-bit CPU but the backend can't handle
-  //        this yet. It's better to fail here than on the backend assertion.
-  if (processorSupportsGPR64() && ABI == "o32") {
-    Diags.Report(diag::err_target_unsupported_abi) << ABI << CPU;
-    return false;
-  }
 
   // 64-bit ABI's require 64-bit CPU's.
   if (!processorSupportsGPR64() && (ABI == "n32" || ABI == "n64")) {
     Diags.Report(diag::err_target_unsupported_abi) << ABI << CPU;
     return false;
   }
 
-  // FIXME: It's valid to use O32 on a mips64/mips64el triple but the backend
-  //        can't handle this yet. It's better to fail here than on the
-  //        backend assertion.
-  if (getTriple().isMIPS64() && ABI == "o32") {
-    Diags.Report(diag::err_target_unsupported_abi_for_triple)
-        << ABI << getTriple().str();
-    return false;
-  }
-
-  // FIXME: It's valid to use N32/N64 on a mips/mipsel triple but the backend
-  //        can't handle this yet. It's better to fail here than on the
-  //        backend assertion.
-  if (getTriple().isMIPS32() && (ABI == "n32" || ABI == "n64")) {
-    Diags.Report(diag::err_target_unsupported_abi_for_triple)
-        << ABI << getTriple().str();
-    return false;
-  }
-
   // -fpxx is valid only for the o32 ABI
   if (FPMode == FPXX && (ABI == "n32" || ABI == "n64")) {
     Diags.Report(diag::err_unsupported_abi_for_opt) << "-mfpxx" << "o32";

clang/test/Driver/mips-abi.c

@@ -9,13 +9,6 @@
 // MIPS32R2-O32: "-target-cpu" "mips32r2"
 // MIPS32R2-O32: "-target-abi" "o32"
 //
-// FIXME: This is a valid combination of options but we reject it at the moment
-//        because the backend can't handle it.
-// RUN: not %clang -target mips-linux-gnu -c %s \
-// RUN:        -march=mips64r2 -mabi=32 2>&1 \
-// RUN:   | FileCheck -check-prefix=MIPS64R2-O32 %s
-// MIPS64R2-O32: error: ABI 'o32' is not supported on CPU 'mips64r2'
-//
 // RUN: %clang -target mips64-linux-gnu -### -c %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=MIPS64R2-N64 %s
 // RUN: %clang -target mips-img-linux-gnu -mips64r2 -### -c %s 2>&1 \

clang/test/Driver/mips-cpu64abi32.c

@@ -0,0 +1,68 @@
+/// Check handling the CPU is 64bit while ABI is O32.
+/// when build for MIPS platforms.
+
+/// abi-n32
+// RUN: %clang -### -c %s --target=mips-linux-gnu -mabi=n32 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-ABI-N32 %s
+// CHECK-ABI-N32: "-target-abi" "n32"
+
+/// abi-64
+// RUN: %clang -### -c %s --target=mips-linux-gnu -mabi=64 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-ABI-64 %s
+// CHECK-ABI-64: "-target-abi" "n64"
+
+
+/// -march=mips3
+// RUN: %clang -### -c %s --target=mips-linux-gnu -march=mips3 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MIPS-MIPS3 %s
+// CHECK-MIPS-MIPS3: "-target-cpu" "mips3" {{.*}} "-target-abi" "o32"
+
+/// -march=mips4
+// RUN: %clang -### -c %s --target=mips-linux-gnu -march=mips4 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MIPS-MIPS4 %s
+// CHECK-MIPS-MIPS4: "-target-cpu" "mips4" {{.*}} "-target-abi" "o32"
+
+/// FIXME: MIPS V is not implemented yet.
+
+/// -march=mips64
+/// RUN: %clang -### -c %s --target=mips-linux-gnu -march=mips64 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MIPS-MIPS64 %s
+// CHECK-MIPS-MIPS64: "-target-cpu" "mips64" {{.*}} "-target-abi" "o32"
+
+/// -march=mips64r2
+/// RUN: %clang -### -c %s --target=mips-linux-gnu -march=mips64r2 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MIPS-MIPS64R2 %s
+// CHECK-MIPS-MIPS64R2: "-target-cpu" "mips64r2" {{.*}} "-target-abi" "o32"
+
+/// -march=mips64r6
+// RUN: %clang -### -c %s --target=mips-linux-gnu -march=mips64r6 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MIPS-MIPS64R6 %s
+// CHECK-MIPS-MIPS64R6: "-target-cpu" "mips64r6" {{.*}} "-target-abi" "o32"
+
+
+/// mipsisa3
+// RUN: %clang -### -c %s --target=mips64-linux-gnu -march=mips3 -mabi=32 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MIPS-MIPSISA3 %s
+// CHECK-MIPS-MIPSISA3: "-target-cpu" "mips3" {{.*}} "-target-abi" "o32"
+
+/// mipsisa4
+// RUN: %clang -### -c %s --target=mips64-linux-gnu -march=mips4 -mabi=32 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MIPS-MIPSISA4 %s
+// CHECK-MIPS-MIPSISA4: "-target-cpu" "mips4" {{.*}} "-target-abi" "o32"
+
+/// FIXME: MIPS V is not implemented yet.
+
+/// mipsisa64
+// RUN: %clang -### -c %s --target=mips64-linux-gnu -march=mips64 -mabi=32 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MIPS-MIPSISA64 %s
+// CHECK-MIPS-MIPSISA64: "-target-cpu" "mips64" {{.*}} "-target-abi" "o32"
+
+/// mipsisa64r2
+// RUN: %clang -### -c %s --target=mips64-linux-gnu -march=mips64r2 -mabi=32 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MIPS-MIPSISA64R2 %s
+// CHECK-MIPS-MIPSISA64R2: "-target-cpu" "mips64r2" {{.*}} "-target-abi" "o32"
+
+/// mipsisa64r6
+// RUN: %clang -### -c %s --target=mips64-linux-gnu -march=mips64r6 -mabi=32 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MIPS-MIPSISA64R6 %s
+// CHECK-MIPS-MIPSISA64R6: "-target-cpu" "mips64r6" {{.*}} "-target-abi" "o32"

llvm/lib/Target/Mips/MipsSubtarget.cpp

@@ -104,8 +104,7 @@ MipsSubtarget::MipsSubtarget(const Triple &TT, StringRef CPU, StringRef FS,
     report_fatal_error("Code generation for MIPS-V is not implemented", false);
 
   // Check if Architecture and ABI are compatible.
-  assert(((!isGP64bit() && isABI_O32()) ||
-          (isGP64bit() && (isABI_N32() || isABI_N64()))) &&
+  assert(((!isGP64bit() && isABI_O32()) || isGP64bit()) &&
          "Invalid  Arch & ABI pair.");
 
   if (hasMSA() && !isFP64bit())