Implement support for big endian arm targets.

Adds support for the big endian arm targets by making the target
endianess flag configurable, adding support for the big endian
calling conventions, rewriting memory access patterns and adding
big endian versions of the runtime functions.
Bug 19418

1 files changed, 37 insertions, 13 deletions

diff --git a/arm/Conventions1.v b/arm/Conventions1.v
index 3eae50ef..888861a5 100644
--- a/arm/Conventions1.v
+++ b/arm/Conventions1.v
@@ -85,15 +85,21 @@ Definition dummy_float_reg := F0.   (**r Used in [Coloring]. *)
 
   For the "softfloat" convention, results of FP types should be passed
   in [R0] or [R0,R1].  This doesn't fit the CompCert register model,
-  so we have code in [arm/PrintAsm.ml] that inserts additional moves
-  to/from [F0]. *)
+  so we have code in [arm/TargetPrinter.ml] that inserts additional moves
+  to/from [F0].
+
+  Concerning endianness for 64bit values in register pairs, the contents
+  of the registers is as if the value had been loaded from memory
+  representation with a single LDM instruction. *)
 
 Definition loc_result (s: signature) : rpair mreg :=
   match s.(sig_res) with
   | None => One R0
   | Some (Tint | Tany32) => One R0
   | Some (Tfloat | Tsingle | Tany64) => One F0
-  | Some Tlong => Twolong R1 R0
+  | Some Tlong => if Archi.big_endian
+                  then Twolong R0 R1
+                  else Twolong R1 R0
   end.
 
 (** The result registers have types compatible with that given in the signature. *)
@@ -102,7 +108,7 @@ Lemma loc_result_type:
   forall sig,
   subtype (proj_sig_res sig) (typ_rpair mreg_type (loc_result sig)) = true.
 Proof.
-  intros. unfold proj_sig_res, loc_result. destruct (sig_res sig) as [[]|]; auto.
+  intros. unfold proj_sig_res, loc_result. destruct (sig_res sig) as [[]|]; destruct Archi.big_endian; auto.
 Qed.
 
 (** The result locations are caller-save registers *)
@@ -112,7 +118,7 @@ Lemma loc_result_caller_save:
   forall_rpair (fun r => is_callee_save r = false) (loc_result s).
 Proof.
   intros.
-  unfold loc_result. destruct (sig_res s) as [[]|]; simpl; auto.
+  unfold loc_result. destruct (sig_res s) as [[]|]; destruct Archi.big_endian; simpl; auto.
 Qed.
 
 (** If the result is in a pair of registers, those registers are distinct and have type [Tint] at least. *)
@@ -124,7 +130,9 @@ Lemma loc_result_pair:
   | Twolong r1 r2 => r1 <> r2 /\ sg.(sig_res) = Some Tlong /\ subtype Tint (mreg_type r1) = true /\ subtype Tint (mreg_type r2) = true
   end.
 Proof.
-  intros; unfold loc_result; destruct (sig_res sg) as [[]|]; auto. intuition congruence. 
+  intros; unfold loc_result; destruct (sig_res sg) as [[]|]; destruct Archi.big_endian; auto.
+  intuition congruence.
+  intuition congruence.
 Qed.
 
 (** ** Location of function arguments *)
@@ -176,11 +184,13 @@ Fixpoint loc_arguments_hf
       then One (R (freg_param fr)) :: loc_arguments_hf tys ir (fr + 1) ofs
       else One (S Outgoing ofs Tsingle) :: loc_arguments_hf tys ir fr (ofs + 1)
   | Tlong :: tys =>
+      let ohi := if Archi.big_endian then 0 else 1 in
+      let olo := if Archi.big_endian then 1 else 0 in
       let ir := align ir 2 in
       if zlt ir 4
-      then Twolong (R (ireg_param (ir + 1))) (R (ireg_param ir)) :: loc_arguments_hf tys (ir + 2) fr ofs
+      then Twolong (R (ireg_param (ir + ohi))) (R (ireg_param (ir + olo))) :: loc_arguments_hf tys (ir + 2) fr ofs
       else let ofs := align ofs 2 in
-           Twolong (S Outgoing (ofs + 1) Tint) (S Outgoing ofs Tint) :: loc_arguments_hf tys ir fr (ofs + 2)
+           Twolong (S Outgoing (ofs + ohi) Tint) (S Outgoing (ofs + olo) Tint) :: loc_arguments_hf tys ir fr (ofs + 2)
   end.
 
 (** For the "softfloat" configuration, as well as for variable-argument functions
@@ -218,9 +228,11 @@ Fixpoint loc_arguments_sf
       One (if zlt ofs 0 then R (freg_param (ofs + 4)) else S Outgoing ofs Tsingle)
       :: loc_arguments_sf tys (ofs + 1)
   | Tlong :: tys =>
+      let ohi := if Archi.big_endian then 0 else 1 in
+      let olo := if Archi.big_endian then 1 else 0 in
       let ofs := align ofs 2 in
-      Twolong (if zlt ofs 0 then R (ireg_param (ofs+1+4)) else S Outgoing (ofs+1) Tint)
-              (if zlt ofs 0 then R (ireg_param (ofs+4)) else S Outgoing ofs Tint)
+      Twolong (if zlt ofs 0 then R (ireg_param (ofs+ohi+4)) else S Outgoing (ofs+ohi) Tint)
+              (if zlt ofs 0 then R (ireg_param (ofs+olo+4)) else S Outgoing (ofs+olo) Tint)
       :: loc_arguments_sf tys (ofs + 2)
   end.
 
@@ -341,9 +353,9 @@ Proof.
   set (ir' := align ir 2) in *.
   assert (ofs <= align ofs 2) by (apply align_le; omega).
   destruct (zlt ir' 4).
-  destruct H. subst p. split; apply ireg_param_caller_save. 
+  destruct H. subst p. split; apply ireg_param_caller_save.
   eapply IHtyl; eauto.
-  destruct H. subst p. split; (split; [ omega | auto ]).
+  destruct H. subst p. split; destruct Archi.big_endian; (split; [ omega | auto ]).
   eapply Y. eapply IHtyl; eauto. omega.
 - (* single *)
   destruct (zlt fr 8); destruct H.
@@ -396,7 +408,7 @@ Proof.
   destruct H.
   destruct (zlt ofs' 0); subst p.
   split; apply ireg_param_caller_save.
-  split; (split; [xomega|auto]).
+  split; destruct Archi.big_endian; (split; [xomega|auto]).
   eapply Y. eapply IHtyl; eauto. omega.
 - (* single *)
   destruct H.
@@ -513,6 +525,12 @@ Proof.
 - (* long *)
   destruct (zlt (align ir 2) 4).
   destruct H. discriminate. destruct H. discriminate. eauto.
+  destruct Archi.big_endian.
+  destruct H. inv H.
+  eapply Zle_trans. 2: apply size_arguments_hf_above. simpl; omega.
+  destruct H. inv H.
+  rewrite <- Zplus_assoc. simpl. apply size_arguments_hf_above.
+  eauto.
   destruct H. inv H.
   rewrite <- Zplus_assoc. simpl. apply size_arguments_hf_above.
   destruct H. inv H.
@@ -556,9 +574,15 @@ Proof.
   eauto.
 - (* long *)
   destruct H.
+  destruct Archi.big_endian.
+  destruct (zlt (align ofs0 2) 0); inv H.
+  eapply Zle_trans. 2: apply size_arguments_sf_above. simpl; xomega.
   destruct (zlt (align ofs0 2) 0); inv H.
   rewrite <- Zplus_assoc. simpl. apply size_arguments_sf_above.
   destruct H.
+  destruct Archi.big_endian.
+  destruct (zlt (align ofs0 2) 0); inv H.
+  rewrite <- Zplus_assoc. simpl. apply size_arguments_sf_above.
   destruct (zlt (align ofs0 2) 0); inv H.
   eapply Zle_trans. 2: apply size_arguments_sf_above. simpl; xomega.
   eauto.