Fix library variants for v7-R soft-float ABI (#532)

We currently build these two library variants for v7-R with the
soft-float ABI:
* armv7r_soft_nofp
* armv7r_soft_vfpv3_d16

The first variant can only be used when the target does not have an FPU,
because it does not include bootcode to enable the FPU. This means that
we don't have any library variants which can be selected for the
single-precision-only FPUs when using the soft-float ABI. For the
hard-float ABI, we solve this by having separate library variants for
vfpv3xd (SP-only) and vfpv3_d16 (SP+DP). This is important for
performance, as it allows the math library to use DP instructions where
available.

We could do the same thing for the soft-float libraries, however these
variants with an FPU are included for completeness, their performance is
less important because a user interested in performance would use the
hard-float ABI. Thesefore I think we should only include the variant for
the minimal FPU, which is vfpv3xd.

These libraries are also used for v8-R AArch32, where this change is
important because -march=armv8-r implies -mfpu=fpv5-sp-d16 by default,
which currently fails to find a library.

CMakeLists.txt

@@ -1777,9 +1777,9 @@ add_library_variants_for_cpu(
 )
 add_library_variants_for_cpu(
     armv7r
-    SUFFIX soft_vfpv3_d16
-    COMPILE_FLAGS "-mfloat-abi=softfp -march=armv7r -mfpu=vfpv3-d16"
-    MULTILIB_FLAGS "--target=armv7r-unknown-none-eabi -mfpu=vfpv3-d16"
+    SUFFIX soft_vfpv3xd
+    COMPILE_FLAGS "-mfloat-abi=softfp -march=armv7r -mfpu=vfpv3xd"
+    MULTILIB_FLAGS "--target=armv7r-unknown-none-eabi -mfpu=vfpv3xd"
     PICOLIBC_BUILD_TYPE "release"
     QEMU_MACHINE "none"
     QEMU_CPU "cortex-r5f"

test/multilib/armv7r.test

@@ -13,7 +13,7 @@
 # RUN: %clang -print-multi-directory --target=armv7r-none-eabihf -mfpu=vfpv3-d16 -mfloat-abi=softfp   | FileCheck --check-prefix=SOFT-VFPV3 %s
 # RUN: %clang -print-multi-directory --target=armv7r-none-eabihf -mfpu=vfpv3-d16 -marm -mfloat-abi=softfp  | FileCheck --check-prefix=SOFT-VFPV3 %s
 # RUN: %clang -print-multi-directory --target=armv7r-none-eabihf -mfpu=vfpv3-d16 -mthumb -mfloat-abi=softfp | FileCheck --check-prefix=SOFT-VFPV3 %s
-# SOFT-VFPV3: arm-none-eabi/armv7r_soft_vfpv3_d16_exn_rtti{{$}}
+# SOFT-VFPV3: arm-none-eabi/armv7r_soft_vfpv3xd_exn_rtti{{$}}
 # SOFT-VFPV3-EMPTY:
 
 # RUN: %clang -print-multi-directory --target=armv7r-none-eabihf -mfpu=vfpv3xd         | FileCheck --check-prefix=VFPV3XD %s

test/multilib/armv8r.test

@@ -6,6 +6,16 @@
 # CHECK: arm-none-eabi/armv7r_soft_nofp_exn_rtti{{$}}
 # CHECK-EMPTY:
 
+# RUN: %clang -print-multi-directory --target=armv8r-none-eabi | FileCheck --check-prefix=SOFT-VFPV3 %s
+# RUN: %clang -print-multi-directory --target=arm-none-eabi -march=armv8-r | FileCheck --check-prefix=SOFT-VFPV3 %s
+# RUN: %clang -print-multi-directory --target=armv8r-none-eabihf -mfloat-abi=softfp | FileCheck --check-prefix=SOFT-VFPV3 %s
+# RUN: %clang -print-multi-directory --target=arm-none-eabihf -mfloat-abi=softfp -march=armv8-r | FileCheck --check-prefix=SOFT-VFPV3 %s
+# RUN: %clang -print-multi-directory --target=arm-none-eabi -march=armv8-r -marm | FileCheck --check-prefix=SOFT-VFPV3 %s
+# RUN: %clang -print-multi-directory --target=arm-none-eabi -march=armv8-r -mthumb | FileCheck --check-prefix=SOFT-VFPV3 %s
+# RUN: %clang -print-multi-directory --target=arm-none-eabi -march=armv8-r -mfpu=fpv5-d16 | FileCheck --check-prefix=SOFT-VFPV3 %s
+# SOFT-VFPV3: arm-none-eabi/armv7r_soft_vfpv3xd_exn_rtti{{$}}
+# SOFT-VFPV3-EMPTY:
+
 # RUN: %clang -print-multi-directory --target=armv8r-none-eabihf -mfpu=vfpv3-d16 | FileCheck --check-prefix=VFPV3 %s
 # RUN: %clang -print-multi-directory --target=armv8r-none-eabihf -mfpu=neon-vfpv3 | FileCheck --check-prefix=VFPV3 %s
 # RUN: %clang -print-multi-directory --target=armv8r-none-eabihf -mfpu=vfpv3 | FileCheck --check-prefix=VFPV3 %s
@@ -18,5 +28,16 @@
 # RUN: %clang -print-multi-directory --target=armv8r-none-eabihf -mfpu=vfpv3-d16 -marm | FileCheck --check-prefix=VFPV3 %s
 # RUN: %clang -print-multi-directory --target=armv8r-none-eabihf -mfpu=vfpv3-d16 -mthumb | FileCheck --check-prefix=VFPV3 %s
 # RUN: %clang -print-multi-directory --target=armv8r-none-eabihf -mcpu=cortex-r52 | FileCheck --check-prefix=VFPV3 %s
+# RUN: %clang -print-multi-directory --target=arm-none-eabihf -march=armv8-r -mfpu=fpv5-d16 | FileCheck --check-prefix=VFPV3 %s
+# RUN: %clang -print-multi-directory --target=arm-none-eabihf -march=armv8-r -mfpu=fp-armv8 | FileCheck --check-prefix=VFPV3 %s
 # VFPV3: arm-none-eabi/armv7r_hard_vfpv3_d16_exn_rtti{{$}}
 # VFPV3-EMPTY:
+
+# RUN: %clang -print-multi-directory --target=armv8r-none-eabihf                       | FileCheck --check-prefix=VFPV3XD %s
+# RUN: %clang -print-multi-directory --target=arm-none-eabihf   -march=armv8-r         | FileCheck --check-prefix=VFPV3XD %s
+# RUN: %clang -print-multi-directory --target=arm-none-eabihf   -march=armv8-r -marm   | FileCheck --check-prefix=VFPV3XD %s
+# RUN: %clang -print-multi-directory --target=arm-none-eabihf   -march=armv8-r -mthumb | FileCheck --check-prefix=VFPV3XD %s
+# RUN: %clang -print-multi-directory --target=arm-none-eabihf -march=armv8-r -mfpu=fpv4-sp-d16 | FileCheck --check-prefix=VFPV3XD %s
+# RUN: %clang -print-multi-directory --target=arm-none-eabihf -march=armv8-r -mfpu=fpv5-sp-d16 | FileCheck --check-prefix=VFPV3XD %s
+# VFPV3XD: arm-none-eabi/armv7r_hard_vfpv3xd_exn_rtti{{$}}
+# VFPV3XD-EMPTY: