[clang][RISCV] Change implicit ARCH for explicitly specified ABI

[benshi001]

Summary

As discussed in
https://github.com/riscv/riscv-toolchain-conventions/issues/13,

the implicit ARCH for explicitly specified ABI should be

ilp32e => rv32e
ilp32 => rv32imac
ilp32f => rv32imacf
ilp32d => rv32imacfd
lp64 => rv64imac
lp64f => rv64imacf
lp64d => rv64imacfd

[MaskRay]

The thing looks weird. My mental model (ppc) is that -march can infer -mabi, not the other way around...

[benshi001]

In D104192#2815757, @MaskRay wrote:

The thing looks weird. My mental model (ppc) is that -march can infer -mabi, not the other way around...

The original way in Driver/Toolchains/Arch/RISCV.cpp is

if (MABI.equals_lower("ilp32e"))
  return "rv32e";
else if (MABI.startswith_lower("ilp32"))
  return "rv32imafdc";
else if (MABI.startswith_lower("lp64"))
  return "rv64imafdc";

So you think we should delete it entirely?

clang/lib/Driver/ToolChains/Arch/RISCV.cpp

StringRef riscv::getRISCVArch(const llvm::opt::ArgList &Args,
   // ilp32e -> rv32e
   // ilp32 | ilp32f | ilp32d -> rv32imafdc
   // lp64 | lp64f | lp64d -> rv64imafdc
   if (const Arg *A = Args.getLastArg(options::OPT_mabi_EQ)) {
     StringRef MABI = A->getValue();
 
     if (MABI.equals_lower("ilp32e"))
       return "rv32e";
-    else if (MABI.startswith_lower("ilp32"))
+    else if (MABI.equals_lower("ilp32"))
+      return "rv32imac";
+    else if (MABI.equals_lower("ilp32f"))
+      return "rv32imafc";
+    else if (MABI.equals_lower("ilp32d"))
       return "rv32imafdc";
-    else if (MABI.startswith_lower("lp64"))
+    else if (MABI.equals_lower("lp64"))
+      return "rv64imac";
+    else if (MABI.equals_lower("lp64f"))
+      return "rv64imafc";
+    else if (MABI.equals_lower("lp64d"))
       return "rv64imafdc";
   }
 
   // 4. Choose a default based on the triple
   //
   // We deviate from GCC's defaults here:
   // - On `riscv{XLEN}-unknown-elf` we default to `rv{XLEN}imac`
   // - On all other OSs we use `rv{XLEN}imafdc` (equivalent to `rv{XLEN}gc`)

clang/test/Driver/riscv-arch.c

 // RUN: %clang -target riscv32-unknown-elf -march=rv32gc -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck %s
 
 // RUN: %clang -target riscv32-unknown-elf -mabi=ilp32 -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=CHECK-ILP32 %s
 
 // CHECK-ILP32:      "-target-feature" "+m"
 // CHECK-ILP32-SAME: {{^}} "-target-feature" "+a"
-// CHECK-ILP32-SAME: {{^}} "-target-feature" "+f"
-// CHECK-ILP32-SAME: {{^}} "-target-feature" "+d"
 // CHECK-ILP32-SAME: {{^}} "-target-feature" "+c"
+// CHECK-ILP32-NOT:  "-target-feature" "+f"
+// CHECK-ILP32-NOT:  "-target-feature" "+d"
 
 // RUN: %clang -target riscv32-unknown-elf -mabi=ilp32f -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=CHECK-ILP32F %s
 
 // CHECK-ILP32F:      "-target-feature" "+m"
 // CHECK-ILP32F-SAME: {{^}} "-target-feature" "+a"
 // CHECK-ILP32F-SAME: {{^}} "-target-feature" "+f"
-// CHECK-ILP32F-SAME: {{^}} "-target-feature" "+d"
 // CHECK-ILP32F-SAME: {{^}} "-target-feature" "+c"
+// CHECK-ILP32F-NOT:  "-target-feature" "+d"
 
 // RUN: %clang -target riscv32-unknown-elf -mabi=ilp32d -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=CHECK-ILP32D %s
 
 // CHECK-ILP32D:      "-target-feature" "+m"
 // CHECK-ILP32D-SAME: {{^}} "-target-feature" "+a"
 // CHECK-ILP32D-SAME: {{^}} "-target-feature" "+f"
 // CHECK-ILP32D-SAME: {{^}} "-target-feature" "+d"

 // RUN: %clang -target riscv64-unknown-elf -march=rv64g -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck %s
 // RUN: %clang -target riscv64-unknown-elf -march=rv64gc -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck %s
 
 // RUN: %clang -target riscv64-unknown-elf -mabi=lp64 -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=CHECK-LP64 %s
 
-// CHECK-LP64: "-target-feature" "+m"
+// CHECK-LP64:      "-target-feature" "+m"
 // CHECK-LP64-SAME: {{^}} "-target-feature" "+a"
-// CHECK-LP64-SAME: {{^}} "-target-feature" "+f"
-// CHECK-LP64-SAME: {{^}} "-target-feature" "+d"
 // CHECK-LP64-SAME: {{^}} "-target-feature" "+c"
+// CHECK-LP64-NOT:  "-target-feature" "+f"
+// CHECK-LP64-NOT:  "-target-feature" "+d"
 
 // RUN: %clang -target riscv64-unknown-elf -mabi=lp64f -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=CHECK-LP64F %s
 
-// CHECK-LP64F: "-target-feature" "+m"
+// CHECK-LP64F:      "-target-feature" "+m"
 // CHECK-LP64F-SAME: {{^}} "-target-feature" "+a"
 // CHECK-LP64F-SAME: {{^}} "-target-feature" "+f"
-// CHECK-LP64F-SAME: {{^}} "-target-feature" "+d"
 // CHECK-LP64F-SAME: {{^}} "-target-feature" "+c"
+// CHECK-LP64F-NOT: "-target-feature" "+d"
 
 // RUN: %clang -target riscv64-unknown-elf -mabi=lp64d -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=CHECK-LP64D %s
 
-// CHECK-LP64D: "-target-feature" "+m"
+// CHECK-LP64D:      "-target-feature" "+m"
 // CHECK-LP64D-SAME: {{^}} "-target-feature" "+a"
 // CHECK-LP64D-SAME: {{^}} "-target-feature" "+f"
 // CHECK-LP64D-SAME: {{^}} "-target-feature" "+d"
 // CHECK-LP64D-SAME: {{^}} "-target-feature" "+c"
 
 // CHECK-NOT: error: invalid arch name '
 
 // RUN: %clang -target riscv32-unknown-elf -march=rv32 -### %s \