RISC-V port and assorted changes

This commits adds code generation for the RISC-V architecture, both in 32- and 64-bit modes.

The generated code was lightly tested using the simulator and cross-binutils from https://riscv.org/software-tools/

This port required the following additional changes:

- Integers: More properties about shrx

- SelectOp: now provides smart constructors for mulhs and mulhu

- SelectDiv, 32-bit integer division and modulus: implement constant propagation, use the new smart constructors mulhs and mulhu.

- Runtime library: if no asm implementation is provided, run the reference C implementation through CompCert.  Since CompCert rejects the definitions of names of special functions such as __i64_shl, the reference implementation now uses "i64_" names, e.g. "i64_shl", and a renaming "i64_ -> __i64_" is performed over the generated assembly file, before assembling and building the runtime library.

- test/: add SIMU make variable to run tests through a simulator

- test/regression/alignas.c: make sure _Alignas and _Alignof are not #define'd by C headers

commit da14495c01cf4f66a928c2feff5c53f09bde837f
Author: Xavier Leroy <xavier.leroy@inria.fr>
Date:   Thu Apr 13 17:36:10 2017 +0200

    RISC-V port, continued

    Now working on Asmgen.

commit 36f36eb3a5abfbb8805960443d087b6a83e86005
Author: Xavier Leroy <xavier.leroy@inria.fr>
Date:   Wed Apr 12 17:26:39 2017 +0200

    RISC-V port, first steps

    This port is based on Prashanth Mundkur's experimental RV32 port and brings it up to date with CompCert, and adds 64-bit support (RV64).  Work in progress.

1 files changed, 446 insertions, 0 deletions

diff --git a/riscV/SelectOp.vp b/riscV/SelectOp.vp
new file mode 100644
index 00000000..b38b7b4d
--- /dev/null
+++ b/riscV/SelectOp.vp
@@ -0,0 +1,446 @@
+(* *********************************************************************)
+(*                                                                     *)
+(*              The Compcert verified compiler                         *)
+(*                                                                     *)
+(*          Xavier Leroy, INRIA Paris-Rocquencourt                     *)
+(*           Prashanth Mundkur, SRI International                      *)
+(*                                                                     *)
+(*  Copyright Institut National de Recherche en Informatique et en     *)
+(*  Automatique.  All rights reserved.  This file is distributed       *)
+(*  under the terms of the INRIA Non-Commercial License Agreement.     *)
+(*                                                                     *)
+(*  The contributions by Prashanth Mundkur are reused and adapted      *)
+(*  under the terms of a Contributor License Agreement between         *)
+(*  SRI International and INRIA.                                       *)
+(*                                                                     *)
+(* *********************************************************************)
+
+(** Instruction selection for operators *)
+
+(** The instruction selection pass recognizes opportunities for using
+  combined arithmetic and logical operations and addressing modes
+  offered by the target processor.  For instance, the expression [x + 1]
+  can take advantage of the "immediate add" instruction of the processor,
+  and on the PowerPC, the expression [(x >> 6) & 0xFF] can be turned
+  into a "rotate and mask" instruction.
+
+  This file defines functions for building CminorSel expressions and
+  statements, especially expressions consisting of operator
+  applications.  These functions examine their arguments to choose
+  cheaper forms of operators whenever possible.
+
+  For instance, [add e1 e2] will return a CminorSel expression semantically
+  equivalent to [Eop Oadd (e1 ::: e2 ::: Enil)], but will use a
+  [Oaddimm] operator if one of the arguments is an integer constant,
+  or suppress the addition altogether if one of the arguments is the
+  null integer.  In passing, we perform operator reassociation
+  ([(e + c1) * c2] becomes [(e * c2) + (c1 * c2)]) and a small amount
+  of constant propagation.
+
+  On top of the "smart constructor" functions defined below,
+  module [Selection] implements the actual instruction selection pass.
+*)
+
+Require Archi.
+Require Import Coqlib.
+Require Import Compopts.
+Require Import AST.
+Require Import Integers.
+Require Import Floats.
+Require Import Op.
+Require Import CminorSel.
+
+Local Open Scope cminorsel_scope.
+
+(** ** Constants **)
+
+Definition addrsymbol (id: ident) (ofs: ptrofs) :=
+  Eop (Oaddrsymbol id ofs) Enil.
+
+Definition addrstack (ofs: ptrofs) :=
+  Eop (Oaddrstack ofs) Enil.
+
+(** ** Integer addition and pointer addition *)
+
+Nondetfunction addimm (n: int) (e: expr) :=
+  if Int.eq n Int.zero then e else
+  match e with
+  | Eop (Ointconst m) Enil => Eop (Ointconst (Int.add n m)) Enil
+  | Eop (Oaddrsymbol s m) Enil   => Eop (Oaddrsymbol s (Ptrofs.add (Ptrofs.of_int n) m)) Enil
+  | Eop (Oaddrstack m) Enil      => Eop (Oaddrstack (Ptrofs.add (Ptrofs.of_int n) m)) Enil
+  | Eop (Oaddimm m) (t ::: Enil) => Eop (Oaddimm(Int.add n m)) (t ::: Enil)
+  | _ => Eop (Oaddimm n) (e ::: Enil)
+  end.
+
+Nondetfunction add (e1: expr) (e2: expr) :=
+  match e1, e2 with
+  | Eop (Ointconst n1) Enil, t2 => addimm n1 t2
+  | t1, Eop (Ointconst n2) Enil => addimm n2 t1
+  | Eop (Oaddimm n1) (t1:::Enil), Eop (Oaddimm n2) (t2:::Enil) =>
+      addimm (Int.add n1 n2) (Eop Oadd (t1:::t2:::Enil))
+  | Eop (Oaddimm n1) (t1:::Enil), Eop (Oaddrstack n2) Enil =>
+      Eop Oadd (Eop (Oaddrstack (Ptrofs.add (Ptrofs.of_int n1) n2)) Enil ::: t1 ::: Enil)
+  | Eop (Oaddrstack n1) Enil, Eop (Oaddimm n2) (t2:::Enil) =>
+      Eop Oadd (Eop (Oaddrstack (Ptrofs.add n1 (Ptrofs.of_int n2))) Enil ::: t2 ::: Enil)
+  | Eop (Oaddimm n1) (t1:::Enil), t2 =>
+      addimm n1 (Eop Oadd (t1:::t2:::Enil))
+  | t1, Eop (Oaddimm n2) (t2:::Enil) =>
+      addimm n2 (Eop Oadd (t1:::t2:::Enil))
+  | _, _ => Eop Oadd (e1:::e2:::Enil)
+  end.
+
+(** ** Integer and pointer subtraction *)
+
+Nondetfunction sub (e1: expr) (e2: expr) :=
+  match e1, e2 with
+  | t1, Eop (Ointconst n2) Enil =>
+      addimm (Int.neg n2) t1
+  | Eop (Oaddimm n1) (t1:::Enil), Eop (Oaddimm n2) (t2:::Enil) =>
+      addimm (Int.sub n1 n2) (Eop Osub (t1:::t2:::Enil))
+  | Eop (Oaddimm n1) (t1:::Enil), t2 =>
+      addimm n1 (Eop Osub (t1:::t2:::Enil))
+  | t1, Eop (Oaddimm n2) (t2:::Enil) =>
+      addimm (Int.neg n2) (Eop Osub (t1:::t2:::Enil))
+  | _, _ => Eop Osub (e1:::e2:::Enil)
+  end.
+
+Nondetfunction negint (e: expr) :=
+  match e with
+  | Eop (Ointconst n) Enil => Eop (Ointconst (Int.neg n)) Enil
+  | _ => Eop Oneg (e ::: Enil)
+  end.
+
+(** ** Immediate shifts *)
+
+Nondetfunction shlimm (e1: expr) (n: int) :=
+  if Int.eq n Int.zero then
+    e1
+  else if negb (Int.ltu n Int.iwordsize) then
+    Eop Oshl (e1 ::: Eop (Ointconst n) Enil ::: Enil)
+  else match e1 with
+    | Eop (Ointconst n1) Enil =>
+        Eop (Ointconst (Int.shl n1 n)) Enil
+    | Eop (Oshlimm n1) (t1:::Enil) =>
+        if Int.ltu (Int.add n n1) Int.iwordsize
+        then Eop (Oshlimm (Int.add n n1)) (t1:::Enil)
+        else Eop (Oshlimm n) (e1:::Enil)
+    | _ =>
+        Eop (Oshlimm n) (e1:::Enil)
+  end.
+
+Nondetfunction shruimm (e1: expr) (n: int) :=
+  if Int.eq n Int.zero then
+    e1
+  else if negb (Int.ltu n Int.iwordsize) then
+    Eop Oshru (e1 ::: Eop (Ointconst n) Enil ::: Enil)
+  else match e1 with
+    | Eop (Ointconst n1) Enil =>
+        Eop (Ointconst (Int.shru n1 n)) Enil
+    | Eop (Oshruimm n1) (t1:::Enil) =>
+        if Int.ltu (Int.add n n1) Int.iwordsize
+        then Eop (Oshruimm (Int.add n n1)) (t1:::Enil)
+        else Eop (Oshruimm n) (e1:::Enil)
+    | _ =>
+        Eop (Oshruimm n) (e1:::Enil)
+    end.
+
+Nondetfunction shrimm (e1: expr) (n: int) :=
+  if Int.eq n Int.zero then
+    e1
+  else if negb (Int.ltu n Int.iwordsize) then
+    Eop Oshr (e1 ::: Eop (Ointconst n) Enil ::: Enil)
+  else match e1 with
+    | Eop (Ointconst n1) Enil =>
+        Eop (Ointconst (Int.shr n1 n)) Enil
+    | Eop (Oshrimm n1) (t1:::Enil) =>
+        if Int.ltu (Int.add n n1) Int.iwordsize
+        then Eop (Oshrimm (Int.add n n1)) (t1:::Enil)
+        else Eop (Oshrimm n) (e1:::Enil)
+    | _ =>
+        Eop (Oshrimm n) (e1:::Enil)
+    end.
+
+(** ** Integer multiply *)
+
+Definition mulimm_base (n1: int) (e2: expr) :=
+  match Int.one_bits n1 with
+  | i :: nil =>
+      shlimm e2 i
+  | i :: j :: nil =>
+      Elet e2 (add (shlimm (Eletvar 0) i) (shlimm (Eletvar 0) j))
+  | _ =>
+      Eop Omul (Eop (Ointconst n1) Enil ::: e2 ::: Enil)
+  end.
+
+Nondetfunction mulimm (n1: int) (e2: expr) :=
+  if Int.eq n1 Int.zero then Eop (Ointconst Int.zero) Enil
+  else if Int.eq n1 Int.one then e2
+  else match e2 with
+  | Eop (Ointconst n2) Enil => Eop (Ointconst (Int.mul n1 n2)) Enil
+  | Eop (Oaddimm n2) (t2:::Enil) => addimm (Int.mul n1 n2) (mulimm_base n1 t2)
+  | _ => mulimm_base n1 e2
+  end.
+
+Nondetfunction mul (e1: expr) (e2: expr) :=
+  match e1, e2 with
+  | Eop (Ointconst n1) Enil, t2 => mulimm n1 t2
+  | t1, Eop (Ointconst n2) Enil => mulimm n2 t1
+  | _, _ => Eop Omul (e1:::e2:::Enil)
+  end.
+
+Definition mulhs (e1: expr) (e2: expr) :=
+  if Archi.ptr64 then
+    Eop Olowlong
+      (Eop (Oshrlimm (Int.repr 32))
+         (Eop Omull (Eop Ocast32signed (e1 ::: Enil) :::
+                     Eop Ocast32signed (e2 ::: Enil) ::: Enil) ::: Enil)
+          ::: Enil)
+  else
+    Eop Omulhs (e1 ::: e2 ::: Enil).
+
+Definition mulhu (e1: expr) (e2: expr) :=
+  if Archi.ptr64 then
+    Eop Olowlong
+      (Eop (Oshrluimm (Int.repr 32))
+         (Eop Omull (Eop Ocast32unsigned (e1 ::: Enil) :::
+                     Eop Ocast32unsigned (e2 ::: Enil) ::: Enil) ::: Enil)
+          ::: Enil)
+  else
+    Eop Omulhu (e1 ::: e2 ::: Enil).
+
+(** ** Bitwise and, or, xor *)
+
+Nondetfunction andimm (n1: int) (e2: expr) :=
+  if Int.eq n1 Int.zero then Eop (Ointconst Int.zero) Enil
+  else if Int.eq n1 Int.mone then e2
+  else match e2 with
+  | Eop (Ointconst n2) Enil => Eop (Ointconst (Int.and n1 n2)) Enil
+  | Eop (Oandimm n2) (t2:::Enil) => Eop (Oandimm (Int.and n1 n2)) (t2:::Enil)
+  | _ => Eop (Oandimm n1) (e2:::Enil)
+  end.
+
+Nondetfunction and (e1: expr) (e2: expr) :=
+  match e1, e2 with
+  | Eop (Ointconst n1) Enil, t2 => andimm n1 t2
+  | t1, Eop (Ointconst n2) Enil => andimm n2 t1
+  | _, _ => Eop Oand (e1:::e2:::Enil)
+  end.
+
+Nondetfunction orimm (n1: int) (e2: expr) :=
+  if Int.eq n1 Int.zero then e2
+  else if Int.eq n1 Int.mone then Eop (Ointconst Int.mone) Enil
+  else match e2 with
+       | Eop (Ointconst n2) Enil => Eop (Ointconst (Int.or n1 n2)) Enil
+       | Eop (Oorimm n2) (t2:::Enil) => Eop (Oorimm (Int.or n1 n2)) (t2:::Enil)
+       | _ => Eop (Oorimm n1) (e2:::Enil)
+  end.
+
+Nondetfunction or (e1: expr) (e2: expr) :=
+  match e1, e2 with
+  | Eop (Ointconst n1) Enil, t2 => orimm n1 t2
+  | t1, Eop (Ointconst n2) Enil => orimm n2 t1
+  | _, _ => Eop Oor (e1:::e2:::Enil)
+  end.
+
+Nondetfunction xorimm (n1: int) (e2: expr) :=
+  if Int.eq n1 Int.zero then e2 else
+  match e2 with
+  | Eop (Ointconst n2) Enil => Eop (Ointconst (Int.xor n1 n2)) Enil
+  | Eop (Oxorimm n2) (t2:::Enil) =>
+      let n := Int.xor n1 n2 in
+      if Int.eq n Int.zero then t2 else Eop (Oxorimm n) (t2:::Enil)
+  | _ => Eop (Oxorimm n1) (e2:::Enil)
+  end.
+
+Nondetfunction xor (e1: expr) (e2: expr) :=
+  match e1, e2 with
+  | Eop (Ointconst n1) Enil, t2 => xorimm n1 t2
+  | t1, Eop (Ointconst n2) Enil => xorimm n2 t1
+  | _, _ => Eop Oxor (e1:::e2:::Enil)
+  end.
+
+(** ** Integer logical negation *)
+
+Definition notint (e: expr) := xorimm Int.mone e.
+
+(** ** Integer division and modulus *)
+
+Definition divs_base (e1: expr) (e2: expr) := Eop Odiv (e1:::e2:::Enil).
+Definition mods_base (e1: expr) (e2: expr) := Eop Omod (e1:::e2:::Enil).
+Definition divu_base (e1: expr) (e2: expr) := Eop Odivu (e1:::e2:::Enil).
+Definition modu_base (e1: expr) (e2: expr) := Eop Omodu (e1:::e2:::Enil).
+
+Definition shrximm (e1: expr) (n2: int) :=
+  if Int.eq n2 Int.zero then e1 else Eop (Oshrximm n2) (e1:::Enil).
+
+(* Alternate definition, not convenient for strength reduction during constant propagation *)
+(*
+(* n2 will be less than 31. *)
+
+Definition shrximm_inner (e1: expr) (n2: int) :=
+  Eop (Oshruimm (Int.sub Int.iwordsize n2))
+      ((Eop (Oshrimm (Int.repr (Int.zwordsize - 1)))
+            (e1 ::: Enil))
+         ::: Enil).
+
+Definition shrximm (e1: expr) (n2: int) :=
+  if Int.eq n2 Int.zero then e1
+  else Eop (Oshrimm n2)
+           ((Eop Oadd (e1 ::: shrximm_inner e1 n2 ::: Enil))
+              ::: Enil).
+*)
+
+(** ** General shifts *)
+
+Nondetfunction shl (e1: expr) (e2: expr) :=
+  match e2 with
+  | Eop (Ointconst n2) Enil => shlimm e1 n2
+  | _ => Eop Oshl (e1:::e2:::Enil)
+  end.
+
+Nondetfunction shr (e1: expr) (e2: expr) :=
+  match e2 with
+  | Eop (Ointconst n2) Enil => shrimm e1 n2
+  | _ => Eop Oshr (e1:::e2:::Enil)
+  end.
+
+Nondetfunction shru (e1: expr) (e2: expr) :=
+  match e2 with
+  | Eop (Ointconst n2) Enil => shruimm e1 n2
+  | _ => Eop Oshru (e1:::e2:::Enil)
+  end.
+
+(** ** Floating-point arithmetic *)
+
+Definition negf (e: expr) :=  Eop Onegf (e ::: Enil).
+Definition absf (e: expr) :=  Eop Oabsf (e ::: Enil).
+Definition addf (e1 e2: expr) :=  Eop Oaddf (e1 ::: e2 ::: Enil).
+Definition subf (e1 e2: expr) :=  Eop Osubf (e1 ::: e2 ::: Enil).
+Definition mulf (e1 e2: expr) :=  Eop Omulf (e1 ::: e2 ::: Enil).
+
+Definition negfs (e: expr) :=  Eop Onegfs (e ::: Enil).
+Definition absfs (e: expr) :=  Eop Oabsfs (e ::: Enil).
+Definition addfs (e1 e2: expr) :=  Eop Oaddfs (e1 ::: e2 ::: Enil).
+Definition subfs (e1 e2: expr) :=  Eop Osubfs (e1 ::: e2 ::: Enil).
+Definition mulfs (e1 e2: expr) :=  Eop Omulfs (e1 ::: e2 ::: Enil).
+
+(** ** Comparisons *)
+
+Nondetfunction compimm (default: comparison -> int -> condition)
+                       (sem: comparison -> int -> int -> bool)
+                       (c: comparison) (e1: expr) (n2: int) :=
+  match c, e1 with
+  | c, Eop (Ointconst n1) Enil =>
+      Eop (Ointconst (if sem c n1 n2 then Int.one else Int.zero)) Enil
+  | Ceq, Eop (Ocmp c) el =>
+      if Int.eq_dec n2 Int.zero then
+        Eop (Ocmp (negate_condition c)) el
+      else if Int.eq_dec n2 Int.one then
+        Eop (Ocmp c) el
+      else
+        Eop (Ointconst Int.zero) Enil
+  | Cne, Eop (Ocmp c) el =>
+      if Int.eq_dec n2 Int.zero then
+        Eop (Ocmp c) el
+      else if Int.eq_dec n2 Int.one then
+        Eop (Ocmp (negate_condition c)) el
+      else
+        Eop (Ointconst Int.one) Enil
+  | _, _ =>
+       Eop (Ocmp (default c n2)) (e1 ::: Enil)
+  end.
+
+Nondetfunction comp (c: comparison) (e1: expr) (e2: expr) :=
+  match e1, e2 with
+  | Eop (Ointconst n1) Enil, t2 =>
+      compimm Ccompimm Int.cmp (swap_comparison c) t2 n1
+  | t1, Eop (Ointconst n2) Enil =>
+      compimm Ccompimm Int.cmp c t1 n2
+  | _, _ =>
+      Eop (Ocmp (Ccomp c)) (e1 ::: e2 ::: Enil)
+  end.
+
+Nondetfunction compu (c: comparison) (e1: expr) (e2: expr) :=
+  match e1, e2 with
+  | Eop (Ointconst n1) Enil, t2 =>
+      compimm Ccompuimm Int.cmpu (swap_comparison c) t2 n1
+  | t1, Eop (Ointconst n2) Enil =>
+      compimm Ccompuimm Int.cmpu c t1 n2
+  | _, _ =>
+      Eop (Ocmp (Ccompu c)) (e1 ::: e2 ::: Enil)
+  end.
+
+Definition compf (c: comparison) (e1: expr) (e2: expr) :=
+  Eop (Ocmp (Ccompf c)) (e1 ::: e2 ::: Enil).
+
+Definition compfs (c: comparison) (e1: expr) (e2: expr) :=
+  Eop (Ocmp (Ccompfs c)) (e1 ::: e2 ::: Enil).
+
+(** ** Integer conversions *)
+
+Definition cast8unsigned (e: expr) := andimm (Int.repr 255) e.
+
+Nondetfunction cast8signed (e: expr) :=
+  match e with
+  | Eop (Ointconst n) Enil => Eop (Ointconst (Int.sign_ext 8 n)) Enil
+  | _ =>  Eop Ocast8signed (e ::: Enil)
+  end.
+
+Definition cast16unsigned (e: expr) := andimm (Int.repr 65535) e.
+
+Nondetfunction cast16signed (e: expr) :=
+  match e with
+  | Eop (Ointconst n) Enil => Eop (Ointconst (Int.sign_ext 16 n)) Enil
+  | _ => Eop Ocast16signed (e ::: Enil)
+  end.
+
+(** ** Floating-point conversions *)
+
+Definition intoffloat  (e: expr) := Eop Ointoffloat (e ::: Enil).
+Definition intuoffloat (e: expr) := Eop Ointuoffloat (e ::: Enil).
+
+Nondetfunction floatofintu (e: expr) :=
+  match e with
+  | Eop (Ointconst n) Enil => Eop (Ofloatconst (Float.of_intu n)) Enil
+  | _ => Eop Ofloatofintu (e ::: Enil)
+  end.
+
+Nondetfunction floatofint (e: expr) :=
+  match e with
+  | Eop (Ointconst n) Enil => Eop (Ofloatconst (Float.of_int n)) Enil
+  | _ => Eop Ofloatofint (e ::: Enil)
+  end.
+
+Definition intofsingle (e: expr) := Eop Ointofsingle (e ::: Enil).
+Definition singleofint (e: expr) := Eop Osingleofint (e ::: Enil).
+
+Definition intuofsingle (e: expr) := Eop Ointuofsingle (e ::: Enil).
+Definition singleofintu (e: expr) := Eop Osingleofintu (e ::: Enil).
+
+Definition singleoffloat (e: expr) := Eop Osingleoffloat (e ::: Enil).
+Definition floatofsingle (e: expr) := Eop Ofloatofsingle (e ::: Enil).
+
+(** ** Recognition of addressing modes for load and store operations *)
+
+Nondetfunction addressing (chunk: memory_chunk) (e: expr) :=
+  match e with
+  | Eop (Oaddrstack n) Enil => (Ainstack n, Enil)
+  | Eop (Oaddrsymbol id ofs) Enil => if Archi.pic_code tt then (Aindexed Ptrofs.zero, e:::Enil) else (Aglobal id ofs, Enil)
+  | Eop (Oaddimm n) (e1:::Enil) => (Aindexed (Ptrofs.of_int n), e1:::Enil)
+  | Eop (Oaddlimm n) (e1:::Enil) => (Aindexed (Ptrofs.of_int64 n), e1:::Enil)
+  | _ => (Aindexed Ptrofs.zero, e:::Enil)
+  end.
+
+(** ** Arguments of builtins *)
+
+Nondetfunction builtin_arg (e: expr) :=
+  match e with
+  | Eop (Ointconst n) Enil => BA_int n
+  | Eop (Oaddrsymbol id ofs) Enil => BA_addrglobal id ofs
+  | Eop (Oaddrstack ofs) Enil => BA_addrstack ofs
+  | Eop Omakelong (Eop (Ointconst h) Enil ::: Eop (Ointconst l) Enil ::: Enil) =>
+        BA_long (Int64.ofwords h l)
+  | Eop Omakelong (h ::: l ::: Enil) => BA_splitlong (BA h) (BA l)
+  | Eload chunk (Ainstack ofs) Enil => BA_loadstack chunk ofs
+  | _ => BA e
+  end.