[Bug target/94959] New: Wrong code gen for MVE intrinsics vldrbq_s32 which fails with assembler `Error: lo register required`

[sripar01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94959

            Bug ID: 94959
           Summary: Wrong code gen for MVE intrinsics vldrbq_s32 which
                    fails with assembler `Error: lo register required`
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sripar01 at gcc dot gnu.org
  Target Milestone: ---

Created attachment 48457
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48457&action=edit
test case

$ arm-none-eabi-gcc -v
Using built-in specs.
COLLECT_GCC=arm-none-eabi-gcc
COLLECT_LTO_WRAPPER=/media/sripar01/2tb_work/Release/build-arm-none-eabi/install/libexec/gcc/arm-none-eabi/10.0.1/lto-wrapper
Target: arm-none-eabi
Configured with: /media/sripar01/2tb_work/Release/src/gcc/configure
--target=arm-none-eabi
--prefix=/media/sripar01/2tb_work/Release/build-arm-none-eabi/install//
--with-gmp=/media/sripar01/2tb_work/Release/build-arm-none-eabi/host-tools
--with-mpfr=/media/sripar01/2tb_work/Release/build-arm-none-eabi/host-tools
--with-mpc=/media/sripar01/2tb_work/Release/build-arm-none-eabi/host-tools
--with-isl=/media/sripar01/2tb_work/Release/build-arm-none-eabi/host-tools
--disable-shared --disable-nls --disable-threads --disable-tls
--enable-checking=yes --enable-languages=c,c++,fortran --with-newlib
--with-multilib-list=rmprofile --with-pkgversion=unknown
Thread model: single
Supported LTO compression algorithms: zlib
gcc version 10.0.1 20200427 (experimental) (unknown)

$arm-none-eabi-gcc new.c -c -Ofast -march=armv8.1-m.main+mve -mfloat-abi=hard

new.c: In function 'foo':
new.c:12351:27: warning: passing argument 1 of '__arm_vldrbq_s32' makes pointer
from integer without a cast [-Wint-conversion]
12351 |     b += __arm_vldrbq_s32(c1);
      |                           ^~
      |                           |
      |                           char
new.c:8600:34: note: expected 'const int8_t *' {aka 'const signed char *'} but
argument is of type 'char'
 8600 | __arm_vldrbq_s32 (int8_t const * __base)
      |                   ~~~~~~~~~~~~~~~^~~~~~
/tmp/cc3Q97vs.s: Assembler messages:
/tmp/cc3Q97vs.s:47: Error: lo register required -- `vldrb.s32 q2,[ip]'


`vldrb.s32 q2,[ip]' --> For vldrbq_s32 MVE intrinsic, only low registers are
allowed as second argument and but current compiler is generating wrong code,
which is failing with assembler as shown above.

The test case added is not a properly written one (char variable c passed to
vldrbq_s32 where as expected is const int8_t *) but this is done to reproduce
the above failure.