[llvm] [RISCV] Move the rest of Zfa FLI instruction handling to lowerConstantFP. (PR #109217)

[Craig Topper via llvm-commits]

topperc wrote:

> This patch is not NFC.
> 
> ```
> ; bin/llc -mtriple=riscv64 -mattr=+zfa,+d test.ll -o -
> define float @test_float(float %x) nounwind {
> entry:
>   %cmp = fcmp ult float %x, 0.000000e+00
>   %sel = select i1 %cmp, float -5.000000e-01, float 5.000000e-01
>   ret float %sel
> }
> 
> define double @test_double(double %x) nounwind {
> entry:
>   %cmp = fcmp ult double %x, 0.000000e+00
>   %sel = select i1 %cmp, double -5.000000e-01, double 5.000000e-01
>   ret double %sel
> }
> ```
> 
> Before:
> 
> ```
> test_float:                             # @test_float
> # %bb.0:                                # %entry
>         fmv.w.x fa5, zero
>         fle.s   a0, fa5, fa0
>         fli.s   fa0, 0.5
>         bnez    a0, .LBB0_2
> # %bb.1:
>         fneg.s  fa0, fa0
> .LBB0_2:                                # %entry
>         ret
> 
> test_double:                            # @test_double
> # %bb.0:                                # %entry
>         fmv.d.x fa5, zero
>         fle.d   a0, fa5, fa0
>         fli.d   fa0, 0.5
>         bnez    a0, .LBB1_2
> # %bb.1:
>         fneg.d  fa0, fa0
> .LBB1_2:                                # %entry
>         ret
> ```
> 
> After:
> 
> ```
> test_float:                             # @test_float
> # %bb.0:                                # %entry
>         fmv.w.x fa5, zero
>         fle.s   a0, fa5, fa0
>         fli.s   fa0, 0.5
>         bnez    a0, .LBB0_2
> # %bb.1:
>         fneg.s  fa0, fa0
> .LBB0_2:                                # %entry
>         ret
> 
> .LCPI1_0:
>         .quad   0x3fe0000000000000              # double 0.5
>         .quad   0xbfe0000000000000              # double -0.5
>         .text
>         .globl  test_double
>         .p2align        2
>         .type   test_double, at function
> test_double:                            # @test_double
> # %bb.0:                                # %entry
>         fmv.d.x fa5, zero
>         fle.d   a0, fa5, fa0
>         xori    a0, a0, 1
>         slli    a0, a0, 3
>         lui     a1, %hi(.LCPI1_0)
>         addi    a1, a1, %lo(.LCPI1_0)
>         add     a0, a1, a0
>         fld     fa0, 0(a0)
>         ret
> ```

Thanks. I'll take look.

https://github.com/llvm/llvm-project/pull/109217