[RISCV] Default to ilp32d/lp64d in RISC-V Linux

[rogfer01]

Summary

When running clang as a native compiler in RISC-V Linux the flag -mabi=ilp32d / -mabi=lp64d is always mandatory. This change makes it the default there.

[asb]

Thank Roger. While we're doing this, I think it would make sense to default to ilp32d on 32-bit Linux? I know the glibc support etc is less mature than for RV64, but it seems the sensible thing to do.

[lenary]

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

385 ↗

(On Diff #212972)

Please may you turn this into a set of if-statements? Nesting ternary operators is a recipe for confusion.

[rogfer01]

ChangeLog:

• Make ilp32d also the default in 32-bit RISC-V Linux
• Do not use nested conditional expressions

[rogfer01]

Thanks @asb @lenary for the review!

I understand that, after this change, we will also want to make -march=rv{32,64}gc the default in Linux as well. Otherwise there will be an ABI mismatch with the default -march=rv{32.64}i in a default invocation.

Does this make sense?

[asb]

In D65634#1618443, @rogfer01 wrote:

Thanks @asb @lenary for the review!

I understand that, after this change, we will also want to make -march=rv{32,64}gc the default in Linux as well. Otherwise there will be an ABI mismatch with the default -march=rv{32.64}i in a default invocation.

Does this make sense?

Yes, that makes sense to me.

[rogfer01]

Thanks for the clarification @asb. I've posted D66003 (depending on D66002) for that.

[luismarques]

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

386 ↗

(On Diff #213812)

When I compile a bare metal GNU toolchain (using https://github.com/riscv/riscv-gnu-toolchain, reports GCC 8.3.0) I seem to get lp64d by default. Should we not match that behaviour?

$ cat test.c
float foo() { return 42.0; }
$ riscv64-unknown-elf-gcc -O2 -S test.c
$ cat test.s
(...)
foo:
        lui     a5,%hi(.LC0)
        flw     fa0,%lo(.LC0)(a5)
(...)

[luismarques]

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

386 ↗

(On Diff #213812)

To clarify, that's a toolchain configured with --enable-multilib.

[lenary]

I think my feeling is that this patch can land and we can change the default abi for baremetal targets in a follow-up patch.

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

386 ↗

(On Diff #213812)

I'm confused by this @luismarques

If I do riscv64-unknown-elf-gcc -c test.c followed by riscv64-unknown-elf-objdump -f test.o, the flags displayed are 0x00000011, which does not include ELF::EF_RISCV_FLOAT_ABI_DOUBLE (0x4), and so suggests gcc is using -mabi=lp64 on baremetal elf targets.

That said, riscv64-unknown-elf-gcc -### -c test.c shows it's invoking all subtools with -march=rv64imafdc and -mabi-lp64d. This is still with --enable-multilib, using riscv64-unknown-elf-gcc (GCC) 8.3.0 and GNU objdump (GNU Binutils) 2.32.

I tried to look at where a default was being set in the gcc repo, and the only thing I can see is that the rv64imafdc/lp64d is the last combination to be generated in the multilib configuration, so they may not have explicitly chosen it as a default. I'm not sure.

[rogfer01]

Thanks for the review @lenary @luismarques

We can indeed look at what defaults we want for baremetal in a later change.

I plan to commit this shortly.

cfe/trunk/lib/Driver/ToolChains/Arch/RISCV.cpp

 StringRef riscv::getRISCVABI(const ArgList &Args, const llvm::Triple &Triple) {
   assert((Triple.getArch() == llvm::Triple::riscv32 ||
           Triple.getArch() == llvm::Triple::riscv64) &&
          "Unexpected triple");
 
   if (const Arg *A = Args.getLastArg(options::OPT_mabi_EQ))
     return A->getValue();
 
-  // FIXME: currently defaults to the soft-float ABIs. Will need to be
-  // expanded to select ilp32f, ilp32d, lp64f, lp64d when appropriate.
+  // RISC-V Linux defaults to ilp32d/lp64d
+  if (Triple.getOS() == llvm::Triple::Linux)
+    return Triple.getArch() == llvm::Triple::riscv32 ? "ilp32d" : "lp64d";
+  else
     return Triple.getArch() == llvm::Triple::riscv32 ? "ilp32" : "lp64";
 }

cfe/trunk/test/Driver/riscv32-toolchain.c

 // CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1/../../../../riscv32-unknown-elf/lib{{/|\\\\}}crt0.o"
 // CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1{{/|\\\\}}crtbegin.o"
 // CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "-L{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1/../../../../riscv32-unknown-elf/lib"
 // CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "-L{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1"
 // CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "-lstdc++" "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
 // CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1{{/|\\\\}}crtend.o"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv32-unknown-linux-gnu \
+// RUN:   -target riscv32-unknown-linux-gnu -mabi=ilp32 \
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_linux_sdk \
 // RUN:   --sysroot=%S/Inputs/multilib_riscv_linux_sdk/sysroot 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV32-LINUX-MULTI-ILP32 %s
 
 // C-RV32-LINUX-MULTI-ILP32: "-fuse-init-array"
 // C-RV32-LINUX-MULTI-ILP32: "{{.*}}/Inputs/multilib_riscv_linux_sdk/lib/gcc/riscv64-unknown-linux-gnu/7.2.0/../../../../riscv64-unknown-linux-gnu/bin{{/|\\\\}}ld"
 // C-RV32-LINUX-MULTI-ILP32: "--sysroot={{.*}}/Inputs/multilib_riscv_linux_sdk/sysroot"
 // C-RV32-LINUX-MULTI-ILP32: "-m" "elf32lriscv"
 // C-RV32-LINUX-MULTI-ILP32: "-dynamic-linker" "/lib/ld-linux-riscv32-ilp32.so.1"
 // C-RV32-LINUX-MULTI-ILP32: "{{.*}}/Inputs/multilib_riscv_linux_sdk/lib/gcc/riscv64-unknown-linux-gnu/7.2.0/lib32/ilp32{{/|\\\\}}crtbegin.o"
 // C-RV32-LINUX-MULTI-ILP32: "-L{{.*}}/Inputs/multilib_riscv_linux_sdk/lib/gcc/riscv64-unknown-linux-gnu/7.2.0/lib32/ilp32"
 // C-RV32-LINUX-MULTI-ILP32: "-L{{.*}}/Inputs/multilib_riscv_linux_sdk/sysroot/lib32/ilp32"
 // C-RV32-LINUX-MULTI-ILP32: "-L{{.*}}/Inputs/multilib_riscv_linux_sdk/sysroot/usr/lib32/ilp32"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv32-unknown-linux-gnu -march=rv32imafd -mabi=ilp32d \
+// RUN:   -target riscv32-unknown-linux-gnu -march=rv32imafd \
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_linux_sdk \
 // RUN:   --sysroot=%S/Inputs/multilib_riscv_linux_sdk/sysroot 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV32-LINUX-MULTI-ILP32D %s
 
 // C-RV32-LINUX-MULTI-ILP32D: "-fuse-init-array"
 // C-RV32-LINUX-MULTI-ILP32D: "{{.*}}/Inputs/multilib_riscv_linux_sdk/lib/gcc/riscv64-unknown-linux-gnu/7.2.0/../../../../riscv64-unknown-linux-gnu/bin{{/|\\\\}}ld"
 // C-RV32-LINUX-MULTI-ILP32D: "--sysroot={{.*}}/Inputs/multilib_riscv_linux_sdk/sysroot"
 // C-RV32-LINUX-MULTI-ILP32D: "-m" "elf32lriscv"

cfe/trunk/test/Driver/riscv64-toolchain.c

 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-elf/8.0.1/../../../../riscv64-unknown-elf/lib{{/|\\\\}}crt0.o"
 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-elf/8.0.1{{/|\\\\}}crtbegin.o"
 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "-L{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-elf/8.0.1/../../../../riscv64-unknown-elf/lib"
 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "-L{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-elf/8.0.1"
 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "-lstdc++" "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-elf/8.0.1{{/|\\\\}}crtend.o"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv64-unknown-linux-gnu \
+// RUN:   -target riscv64-unknown-linux-gnu -mabi=lp64 \
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_linux_sdk \
 // RUN:   --sysroot=%S/Inputs/multilib_riscv_linux_sdk/sysroot 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV64-LINUX-MULTI-LP64 %s
 
 // C-RV64-LINUX-MULTI-LP64: "-fuse-init-array"
 // C-RV64-LINUX-MULTI-LP64: "{{.*}}/Inputs/multilib_riscv_linux_sdk/lib/gcc/riscv64-unknown-linux-gnu/7.2.0/../../../../riscv64-unknown-linux-gnu/bin{{/|\\\\}}ld"
 // C-RV64-LINUX-MULTI-LP64: "--sysroot={{.*}}/Inputs/multilib_riscv_linux_sdk/sysroot"
 // C-RV64-LINUX-MULTI-LP64: "-m" "elf64lriscv"
 // C-RV64-LINUX-MULTI-LP64: "-dynamic-linker" "/lib/ld-linux-riscv64-lp64.so.1"
 // C-RV64-LINUX-MULTI-LP64: "{{.*}}/Inputs/multilib_riscv_linux_sdk/lib/gcc/riscv64-unknown-linux-gnu/7.2.0/lib64/lp64{{/|\\\\}}crtbegin.o"
 // C-RV64-LINUX-MULTI-LP64: "-L{{.*}}/Inputs/multilib_riscv_linux_sdk/lib/gcc/riscv64-unknown-linux-gnu/7.2.0/lib64/lp64"
 // C-RV64-LINUX-MULTI-LP64: "-L{{.*}}/Inputs/multilib_riscv_linux_sdk/sysroot/lib64/lp64"
 // C-RV64-LINUX-MULTI-LP64: "-L{{.*}}/Inputs/multilib_riscv_linux_sdk/sysroot/usr/lib64/lp64"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv64-unknown-linux-gnu -march=rv64imafd -mabi=lp64d \
+// RUN:   -target riscv64-unknown-linux-gnu -march=rv64imafd \
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_linux_sdk \
 // RUN:   --sysroot=%S/Inputs/multilib_riscv_linux_sdk/sysroot 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV64-LINUX-MULTI-LP64D %s
 
 // C-RV64-LINUX-MULTI-LP64D: "-fuse-init-array"
 // C-RV64-LINUX-MULTI-LP64D: "{{.*}}/Inputs/multilib_riscv_linux_sdk/lib/gcc/riscv64-unknown-linux-gnu/7.2.0/../../../../riscv64-unknown-linux-gnu/bin{{/|\\\\}}ld"
 // C-RV64-LINUX-MULTI-LP64D: "--sysroot={{.*}}/Inputs/multilib_riscv_linux_sdk/sysroot"
 // C-RV64-LINUX-MULTI-LP64D: "-m" "elf64lriscv"

cfe/trunk/test/Preprocessor/riscv-target-features.c

 // CHECK-D-EXT: __riscv_fsqrt 1
 
 // RUN: %clang -target riscv32-unknown-linux-gnu -march=rv32ic -x c -E -dM %s \
 // RUN: -o - | FileCheck --check-prefix=CHECK-C-EXT %s
 // RUN: %clang -target riscv64-unknown-linux-gnu -march=rv64ic -x c -E -dM %s \
 // RUN: -o - | FileCheck --check-prefix=CHECK-C-EXT %s
 // CHECK-C-EXT: __riscv_compressed 1
 
-// RUN: %clang -target riscv32-unknown-linux-gnu -march=rv32ifd -x c -E -dM %s \
+// RUN: %clang -target riscv32-unknown-linux-gnu -march=rv32ifd -mabi=ilp32 -x c -E -dM %s \
 // RUN: -o - | FileCheck --check-prefix=CHECK-SOFT %s
-// RUN: %clang -target riscv64-unknown-linux-gnu -march=rv64ifd -x c -E -dM %s \
+// RUN: %clang -target riscv64-unknown-linux-gnu -march=rv64ifd -mabi=lp64 -x c -E -dM %s \
 // RUN: -o - | FileCheck --check-prefix=CHECK-SOFT %s
 // CHECK-SOFT: __riscv_float_abi_soft 1
 // CHECK-SOFT-NOT: __riscv_float_abi_single
 // CHECK-SOFT-NOT: __riscv_float_abi_double
 
 // RUN: %clang -target riscv32-unknown-linux-gnu -march=rv32ifd -mabi=ilp32f -x c -E -dM %s \
 // RUN: -o - | FileCheck --check-prefix=CHECK-SINGLE %s
 // RUN: %clang -target riscv64-unknown-linux-gnu -march=rv64ifd -mabi=lp64f -x c -E -dM %s \
 // RUN: -o - | FileCheck --check-prefix=CHECK-SINGLE %s
 // CHECK-SINGLE: __riscv_float_abi_single 1
 // CHECK-SINGLE-NOT: __riscv_float_abi_soft
 // CHECK-SINGLE-NOT: __riscv_float_abi_double
 
-// RUN: %clang -target riscv32-unknown-linux-gnu -march=rv32ifd -mabi=ilp32d -x c -E -dM %s \
+// RUN: %clang -target riscv32-unknown-linux-gnu -march=rv32ifd -x c -E -dM %s \
 // RUN: -o - | FileCheck --check-prefix=CHECK-DOUBLE %s
-// RUN: %clang -target riscv64-unknown-linux-gnu -march=rv64ifd -mabi=lp64d -x c -E -dM %s \
+// RUN: %clang -target riscv64-unknown-linux-gnu -march=rv64ifd -x c -E -dM %s \
 // RUN: -o - | FileCheck --check-prefix=CHECK-DOUBLE %s
 // CHECK-DOUBLE: __riscv_float_abi_double 1
 // CHECK-DOUBLE-NOT: __riscv_float_abi_soft
 // CHECK-DOUBLE-NOT: __riscv_float_abi_single