Be less opinionated (and more accurate) when evaluating saturated arithmetic

[LilithHafner]

Seems like 1 instruction to 4 (branchless) instructions for these two cases:

julia> function sat_mul(x::UInt, y::UInt)
           w = widemul(x,y)
           w2 = w % UInt
           w2 == w ? w2 : typemax(UInt)
       end
sat_mul (generic function with 2 methods)

julia> function sat_plus(x::Int, y::Int)
           z, o = Base.Checked.add_with_overflow(x, y)
           o ? x < 0 ? typemin(Int) : typemax(Int) : z
       end
sat_plus (generic function with 1 method)

julia> @code_native sat_mul(UInt(2), UInt(2))
	.text
	.file	"sat_mul"
	.globl	julia_sat_mul_3459              // -- Begin function julia_sat_mul_3459
	.p2align	2
	.type	julia_sat_mul_3459,@function
julia_sat_mul_3459:                     // @julia_sat_mul_3459
; Function Signature: sat_mul(UInt64, UInt64)
; ┌ @ REPL[57]:1 within `sat_mul`
// %bb.0:                               // %top
; │ @ REPL[57] within `sat_mul`
	//DEBUG_VALUE: sat_mul:x <- $x0
	//DEBUG_VALUE: sat_mul:x <- $x0
	//DEBUG_VALUE: sat_mul:y <- $x1
	//DEBUG_VALUE: sat_mul:y <- $x1
	stp	x29, x30, [sp, #-16]!           // 16-byte Folded Spill
	mov	x29, sp
; │ @ REPL[57]:2 within `sat_mul`
; │┌ @ number.jl:277 within `widemul`
; ││┌ @ int.jl:998 within `*`
	mul	x8, x0, x1
	umulh	x9, x0, x1
	cmp	xzr, x9
	csinv	x0, x8, xzr, eq
; │└└
; │ @ REPL[57]:4 within `sat_mul`
	ldp	x29, x30, [sp], #16             // 16-byte Folded Reload
	ret
.Lfunc_end0:
	.size	julia_sat_mul_3459, .Lfunc_end0-julia_sat_mul_3459
; └
                                        // -- End function
	.section	".note.GNU-stack","",@progbits

julia> @code_native *(UInt(2), UInt(2))
	.text
	.file	"*"
	.globl	"julia_*_3466"                  // -- Begin function julia_*_3466
	.p2align	2
	.type	"julia_*_3466",@function
"julia_*_3466":                         // @"julia_*_3466"
; Function Signature: *(UInt64, UInt64)
; ┌ @ int.jl:88 within `*`
// %bb.0:                               // %top
; │ @ int.jl within `*`
	//DEBUG_VALUE: *:x <- $x0
	//DEBUG_VALUE: *:x <- $x0
	//DEBUG_VALUE: *:y <- $x1
	//DEBUG_VALUE: *:y <- $x1
	stp	x29, x30, [sp, #-16]!           // 16-byte Folded Spill
	mov	x29, sp
; │ @ int.jl:88 within `*`
	mul	x0, x1, x0
	ldp	x29, x30, [sp], #16             // 16-byte Folded Reload
	ret
.Lfunc_end0:
	.size	"julia_*_3466", .Lfunc_end0-"julia_*_3466"
; └
                                        // -- End function
	.section	".note.GNU-stack","",@progbits

julia> @code_native sat_plus(1,1)
	.text
	.file	"sat_plus"
	.globl	julia_sat_plus_3469             // -- Begin function julia_sat_plus_3469
	.p2align	2
	.type	julia_sat_plus_3469,@function
julia_sat_plus_3469:                    // @julia_sat_plus_3469
; Function Signature: sat_plus(Int64, Int64)
; ┌ @ REPL[58]:1 within `sat_plus`
// %bb.0:                               // %top
; │ @ REPL[58] within `sat_plus`
	//DEBUG_VALUE: sat_plus:x <- $x0
	//DEBUG_VALUE: sat_plus:x <- $x0
	//DEBUG_VALUE: sat_plus:y <- $x1
	//DEBUG_VALUE: sat_plus:y <- $x1
	stp	x29, x30, [sp, #-16]!           // 16-byte Folded Spill
	mov	x29, sp
; │ @ REPL[58]:3 within `sat_plus`
	adds	x8, x0, x1
	asr	x9, x8, #63
	eor	x9, x9, #0x8000000000000000
	csel	x0, x9, x8, vs
	ldp	x29, x30, [sp], #16             // 16-byte Folded Reload
	ret
.Lfunc_end0:
	.size	julia_sat_plus_3469, .Lfunc_end0-julia_sat_plus_3469
; └
                                        // -- End function
	.section	".note.GNU-stack","",@progbits

julia> @code_native +(1,1)
	.text
	.file	"+"
	.globl	"julia_+_3474"                  // -- Begin function julia_+_3474
	.p2align	2
	.type	"julia_+_3474",@function
"julia_+_3474":                         // @"julia_+_3474"
; Function Signature: +(Int64, Int64)
; ┌ @ int.jl:87 within `+`
// %bb.0:                               // %top
; │ @ int.jl within `+`
	//DEBUG_VALUE: +:x <- $x0
	//DEBUG_VALUE: +:x <- $x0
	//DEBUG_VALUE: +:y <- $x1
	//DEBUG_VALUE: +:y <- $x1
	stp	x29, x30, [sp, #-16]!           // 16-byte Folded Spill
	mov	x29, sp
; │ @ int.jl:87 within `+`
	add	x0, x1, x0
	ldp	x29, x30, [sp], #16             // 16-byte Folded Reload
	ret
.Lfunc_end0:
	.size	"julia_+_3474", .Lfunc_end0-"julia_+_3474"
; └
                                        // -- End function
	.section	".note.GNU-stack","",@progbits

[LilithHafner]

Test failures look unrelated