arm-none-eabi-gcc 10.2 not generating SMLALTT, SMLALTB, SMLALBT instructions

arm-none-eabi-gcc 10.2 not generating SMLALTT, SMLALTB, SMLALBT instructions

[Andrew Jeddeloh]

Please reply to me or CC me in addition to the list as I am not subscribed.

I have code essentially like this:
int32_t var1 = <value>, var2 = <value>;
int64_t acc = <value>;
acc += (int64_t)((int16_t)(var1 & 0xffff) * (int16_t)((var2 & 0xffff0000)>>16))

which is essentially the same as this test case:
https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/testsuite/gcc.target/arm/smlaltt-1.c;hb=HEAD

but instead of generating a SMLALBT or SMLALTB instruction, it
generates a ASRS then a SMLALBB. This is especially problematic for me
because it ends up using an extra register which causes extra
loads/stores in a tight loop.

Is there something I'm missing to get it to generate SMLALxy
instructions other than SMLALBB

Here is the exact code in question:
https://gist.github.com/ajeddeloh/734a2d7e44df219d38d327b5cf82f504

I've stripped most of the unrelated code out. The exact code in
question is in the loop.

Thanks for your help!
 - Andrew