cmd/compile: sign or zero extend for 32 bit equality on riscv64
For 32 bit equality (Eq32), rather than always zero extending to 64 bits,
sign extend for signed types and zero extend for unsigned types. This makes
no difference to the equality test (via SUB), however it increases the
likelihood of avoiding unnecessary sign or zero extension simply for the
purpose of equality testing.
While here, replace the Neq* rules with (Not (Eq*)) - this makes no
difference to the generated code (as the intermediates get expanded and
eliminated), however it means that changes to the equality rules also
reflect in the inequality rules.
As an example, the following:
lw t0,956(t0)
slli t0,t0,0x20
srli t0,t0,0x20
li t1,1
bne t1,t0,278fc
Becomes:
lw t0,1024(t0)
li t1,1
bne t1,t0,278b0
Removes almost 1000 instructions from the Go binary on riscv64.
Change-Id: Iac60635f494f6db87faa47752bd1cc16e6b5967f
Reviewed-on: https://go-review.googlesource.com/c/go/+/516595
Run-TryBot: Joel Sing <joel@sing.id.au> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: M Zhuo <mzh@golangcn.org> Reviewed-by: Michael Knyszek <mknyszek@google.com>