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author | Xavier Leroy <xavier.leroy@college-de-france.fr> | 2019-06-17 09:43:34 +0200 |
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committer | Xavier Leroy <xavierleroy@users.noreply.github.com> | 2019-06-17 13:58:35 +0200 |
commit | 37cebaabf65fe3961b9932c6582d15b3b676cefe (patch) | |
tree | b96ff1252181269ba5ae8fdad3cea9784c571b52 /powerpc | |
parent | ddb2c968e6c57d2117434f169471d87f643d831a (diff) | |
download | compcert-37cebaabf65fe3961b9932c6582d15b3b676cefe.tar.gz compcert-37cebaabf65fe3961b9932c6582d15b3b676cefe.zip |
Perform constant propagation and strength reduction on conditional moves
A conditional move whose condition is statically known becomes a regular move.
Otherwise, the condition can sometimes be simplified by strength reduction.
Diffstat (limited to 'powerpc')
-rw-r--r-- | powerpc/ConstpropOp.vp | 12 | ||||
-rw-r--r-- | powerpc/ConstpropOpproof.v | 26 |
2 files changed, 36 insertions, 2 deletions
diff --git a/powerpc/ConstpropOp.vp b/powerpc/ConstpropOp.vp index 2d492b66..cf1dc6e8 100644 --- a/powerpc/ConstpropOp.vp +++ b/powerpc/ConstpropOp.vp @@ -16,7 +16,7 @@ Require Import Coqlib Compopts. Require Import AST Integers Floats. Require Import Op Registers. -Require Import ValueDomain. +Require Import ValueDomain ValueAOp. (** * Converting known values to constants *) @@ -95,6 +95,15 @@ Nondetfunction make_cmp (c: condition) (args: list reg) (vl: list aval) := make_cmp_base c args vl end. +Definition make_select (c: condition) (ty: typ) + (r1 r2: reg) (args: list reg) (vl: list aval) := + match resolve_branch (eval_static_condition c vl) with + | Some b => (Omove, (if b then r1 else r2) :: nil) + | None => + let (c', args') := cond_strength_reduction c args vl in + (Osel c' ty, r1 :: r2 :: args') + end. + Definition make_addimm (n: int) (r: reg) := if Int.eq n Int.zero then (Omove, r :: nil) @@ -303,6 +312,7 @@ Nondetfunction op_strength_reduction | Oshrl, r1 :: r2 :: nil, v1 :: I n2 :: nil => make_shrlimm n2 r1 r2 | Oshrlu, r1 :: r2 :: nil, v1 :: I n2 :: nil => make_shrluimm n2 r1 r2 | Ocmp c, args, vl => make_cmp c args vl + | Osel c ty, r1 :: r2 :: args, v1 :: v2 :: vl => make_select c ty r1 r2 args vl | Omulf, r1 :: r2 :: nil, v1 :: F n2 :: nil => make_mulfimm n2 r1 r1 r2 | Omulf, r1 :: r2 :: nil, F n1 :: v2 :: nil => make_mulfimm n1 r2 r1 r2 | Omulfs, r1 :: r2 :: nil, v1 :: FS n2 :: nil => make_mulfsimm n2 r1 r1 r2 diff --git a/powerpc/ConstpropOpproof.v b/powerpc/ConstpropOpproof.v index fe061e5b..38daefe4 100644 --- a/powerpc/ConstpropOpproof.v +++ b/powerpc/ConstpropOpproof.v @@ -14,7 +14,7 @@ Require Import Coqlib Compopts. Require Import Integers Floats Values Memory Globalenvs Events. -Require Import Op Registers RTL ValueDomain. +Require Import Op Registers RTL ValueDomain ValueAOp ValueAnalysis. Require Import ConstpropOp. Local Transparent Archi.ptr64. @@ -211,6 +211,28 @@ Proof. - apply make_cmp_base_correct; auto. Qed. +Lemma make_select_correct: + forall c ty r1 r2 args vl, + vl = map (fun r => AE.get r ae) args -> + let (op', args') := make_select c ty r1 r2 args vl in + exists v, eval_operation ge (Vptr sp Ptrofs.zero) op' rs##args' m = Some v + /\ Val.lessdef (Val.select (eval_condition c rs##args m) rs#r1 rs#r2 ty) v. +Proof. + unfold make_select; intros. + destruct (resolve_branch (eval_static_condition c vl)) as [b|] eqn:RB. +- exists (if b then rs#r1 else rs#r2); split. ++ simpl. destruct b; auto. ++ destruct (eval_condition c rs##args m) as [b'|] eqn:EC; simpl; auto. + assert (b = b'). + { eapply resolve_branch_sound; eauto. + rewrite <- EC. apply eval_static_condition_sound with bc. + subst vl. exact (aregs_sound _ _ _ args MATCH). } + subst b'. apply Val.lessdef_normalize. +- generalize (cond_strength_reduction_correct c args vl H). + destruct (cond_strength_reduction c args vl) as [cond' args']; intros EQ. + econstructor; split. simpl; eauto. rewrite EQ; auto. +Qed. + Lemma make_addimm_correct: forall n r, let (op, args) := make_addimm n r in @@ -715,6 +737,8 @@ Proof. InvApproxRegs; SimplVM; inv H0. apply make_shrluimm_correct; auto. (* cmp *) inv H0. apply make_cmp_correct; auto. +(* select *) + inv H0. apply make_select_correct; congruence. (* mulf *) InvApproxRegs; SimplVM; inv H0. rewrite <- H2. apply make_mulfimm_correct; auto. InvApproxRegs; SimplVM; inv H0. fold (Val.mulf (Vfloat n1) rs#r2). |