Raymond Toy pushed to branch issue-175-simplify-float-compare-vops at cmucl / cmucl

Commits: d10df309 by Raymond Toy at 2023-03-09T13:18:24-08:00 For float <, allow x to be a descriptor instead of y.

Since the implementation of x < y reverses args to do y > x, it can be helpful if x can be a descriptor. Make it so.

- - - - - e89872a2 by Raymond Toy at 2023-03-10T08:14:14-08:00 Replace cond with simple if

The cond expression can be replaced by a much simpler if, which mirrors how the sparc and ppc ports handle the not-p jumps.

- - - - -

1 changed file:

- src/compiler/x86/float-sse2.lisp

Changes:

===================================== src/compiler/x86/float-sse2.lisp ===================================== @@ -963,19 +963,17 @@ (inst ,inst x y)) (descriptor-reg (inst ,inst x (,ea y)))) - (cond (not-p - ;; Instead of x > y, we're doing x <= y and want - ;; to jmp when x <= y. If NaN occurrs we also - ;; want to jump. x <= y means CF = 1 or ZF = 1. - ;; When NaN occurs, ZF, PF, and CF are all set. - ;; Hence, we can just test for x <= y. - (inst jmp :be target)) - (t - ;; If there's NaN, the ZF, PF, and CF bits are - ;; set. We only want to jmp to the target when - ;; x > y. This happens if CF = 0. Hence, we - ;; will not jmp to the target if NaN occurred. - (inst jmp :a target)))))))) + ;; When a NaN occurs, comis sets ZF, PF, and CF = 1. In + ;; the normal case (not-p false), we want to jump to the + ;; target when x > y. This happens when CF = 0. Hence, + ;; we won't jump to the target when there's a NaN, as + ;; desired. + ;; + ;; For the not-p case, we want to jump to target when x + ;; <= y. This means CF = 1 or ZF = 1. But NaN sets + ;; these bits too, so we jump to the target for NaN or x + ;; <= y, as desired. + (inst jmp (if (not not-p) :a :be) target)))))) (frob > single comiss) (frob > double comisd))

@@ -990,29 +988,22 @@ (sc-type (symbolicate size "-REG")) (inherit (symbolicate size "-FLOAT-COMPARE"))) `(define-vop (,name ,inherit) + (:args (x :scs (,sc-type descriptor-reg)) + (y :scs (,sc-type))) (:translate ,op) (:info target not-p) - (:temporary (:sc ,sc-type) load-y) + (:temporary (:sc ,sc-type) load-x) (:generator 3 - (sc-case y + ;; Note: x < y is the same as y > x. We reverse the + ;; args to reduce the number of jump instructions + ;; needed. Then the logic for the branches is the same + ;; as for the case y > x above. + (sc-case x (,sc-type (inst ,inst y x)) (descriptor-reg - (inst ,mover load-y (,ea y)) - (inst ,inst load-y x))) - (cond (not-p - ;; Instead of x < y, we're doing x >= y and want - ;; to jmp when x >= y. But x >=y is the same as - ;; y <= x, so if we swap the args, we can apply - ;; the same logic we use for > not-p case above. - (inst jmp :be target)) - (t - ;; We want to jump when x < y. This is the same - ;; as jumping when y > x. So if we reverse the - ;; args, we can apply the same logic as we did - ;; above for the > vop. - - (inst jmp :a target)))))))) + (inst ,inst y (,ea x)))) + (inst jmp (if (not not-p) :a :be) target)))))) (frob < single comiss movss) (frob < double comisd movsd))

View it on GitLab: https://gitlab.common-lisp.net/cmucl/cmucl/-/compare/9cb12348b64546ee281c5ff...