1bd3a8af85
The attached patch eliminates a redundant zero extend from the AArch64 backend. Given the following C code:
unsigned long long foo(unsigned a)
{
return ~a;
}
prior to this patch, AArch64 GCC at -O2 generates:
foo:
mvn w0, w0
uxtw x0, w0
ret
but the uxtw is redundant, since the mvn clears the upper half of the x0 register. After applying this patch, GCC at -O2 gives:
foo:
mvn w0, w0
ret
Testing:
Added regression test which passes after applying the change to aarch64.md.
Full bootstrap and regression on aarch64-linux with no additional failures.
* config/aarch64/aarch64.md (*one_cmpl_zero_extend): New.
* gcc.target/aarch64/mvn_zero_ext.c: New test.
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README
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