From f2b28b4124015718dc4b392e00f4aade4eedc11c Mon Sep 17 00:00:00 2001
From: Alex AUVOLAT <alex.auvolat@ens.fr>
Date: Thu, 2 Jan 2014 23:20:01 +0100
Subject: Implement jr/jalr/jer/jner/jltr/jler/jltru/jleru ; add simplification
 to sched.

---
 cpu/alu.ml        | 68 +++++++++++++++++++++++++++++++++++++++++++++----------
 cpu/cpu.ml        | 24 ++++++++++++++++----
 sched/simplify.ml |  8 +++++++
 3 files changed, 84 insertions(+), 16 deletions(-)

diff --git a/cpu/alu.ml b/cpu/alu.ml
index cf33cd2..a0115a4 100644
--- a/cpu/alu.ml
+++ b/cpu/alu.ml
@@ -1,5 +1,20 @@
 open Netlist_gen
 
+let rec rep n k =
+    if n = 1 then k
+    else
+        let s = rep (n/2) k in
+        if n mod 2 = 0 then s ++ s else s ++ s ++ k
+
+let rec eq_c n v c = (* v is a value, c is a constant *)
+    if n = 1 then
+        if c = 1 then v else not v
+    else
+        (eq_c 1 (v ** 0) (c mod 2)) ^& (eq_c (n-1) (v % (1, n-1)) (c/2))
+
+let rec sign_extend n_a n_dest a =
+    a ++ rep (n_dest - n_a) (a ** (n_a - 1))
+
 let fulladder a b c =
        let s = a ^^ b ^^ c in
        let r = (a ^& b) ^| ((a ^^ b) ^& c) in
@@ -16,18 +31,47 @@ let nadder_nocarry n a b =
     let a, b = nadder n a b (const "0") in
     ignore b a
 
-let rec rep n k =
-    if n = 1 then k
-    else
-        let s = rep (n/2) k in
-        if n mod 2 = 0 then s ++ s else s ++ s ++ k
-
-let rec sign_extend n_a n_dest a =
-    a ++ rep (n_dest - n_a) (a ** (n_a - 1))
+let rec eq_n n a b =
+    if n = 1 then
+        not (a ^^ b)
+    else 
+        (not ((a ** 0) ^^ (b ** 0)))
+        ^& (eq_n (n-1) (a % (1, n-1)) (b % (1, n-1)))
 
-let rec eq_c n v c = (* v is a value, c is a constant *)
+let rec ne_n n a b =
     if n = 1 then
-        if c = 1 then v else not v
-    else
-        (eq_c 1 (v ** 0) (c mod 2)) ^& (eq_c (n-1) (v % (1, n-1)) (c/2))
+        a ^^ b
+    else 
+        ((a ** 0) ^^ (b ** 0))
+        ^| (ne_n (n-1) (a % (1, n-1)) (b % (1, n-1)))
+
+let rec lt_n n a b =
+    const "0"       (* TODO : less than *)
+
+let rec ult_n n a b =
+    const "0"       (* TODO : less than, unsigned *)
+
+let rec le_n n a b =
+    const "0"       (* TODO : less than or equal *)
+
+let rec ule_n n a b =
+    const "0"       (* TODO : less than or equal, unsigned *)
 
+let alu_comparer n f0 f a b =
+    (*
+        f0  f   action
+        --  -   ------
+        0   0   equal
+        0   1   not equal
+        0   2   equal
+        0   3   not equal
+        1   0   lt
+        1   1   le
+        1   2   lt unsigned
+        1   3   le unsigned
+    *)
+    let eq_ne = mux (f ** 0) (eq_n n a b) (ne_n n a b) in
+    let lte_signed = mux (f ** 0) (lt_n n a b) (le_n n a b) in
+    let lte_unsigned = mux (f ** 0) (ult_n n a b) (ule_n n a b) in
+    let lte = mux (f ** 1) lte_signed lte_unsigned in
+    mux f0 eq_ne lte
diff --git a/cpu/cpu.ml b/cpu/cpu.ml
index 8a31c9e..c70d6e2 100644
--- a/cpu/cpu.ml
+++ b/cpu/cpu.ml
@@ -95,8 +95,13 @@ let rl, rh, i, ex, exf, pc =
     let ra = mux read_ihi ra (nadder_nocarry 16 pc (one 16)) in
     let ihi = mux read_ihi (zeroes 8) ram_read in
 
-    let exec = ignore (save_next_read_ihi read_ilow) read_ihi in
-    let i = ilow ++ ihi in
+    let read_ilow = save_next_read_ihi read_ilow in
+    (* When execution has just been read, exec is true, and exec is false the rest of the time *)
+    let exec = read_ihi in
+    (* Keep same instruction in register until new instruction is read *)
+    let si, save_i = loop 16 in
+    let i = mux exec (reg 16 si) (ilow ++ ihi) in
+    let i = save_i i in
 
     (* Execute instruction if exec is set *)
     let next_pc = nadder_nocarry 16 pc (two 16) in
@@ -127,9 +132,20 @@ let rl, rh, i, ex, exf, pc =
     let next_pc = mux instr_j next_pc (nadder_nocarry 16 pc (sign_extend 11 16 i_jd)) in
     (* instruction : jal *)
     let instr_jal = exec ^& eq_c 5 i_i 0b01001 in
-    let wr = mux instr_jal wr (const "011") in
-    let rwd = mux instr_jal rwd next_pc in
     let next_pc = mux instr_jal next_pc (nadder_nocarry 16 pc (sign_extend 11 16 i_jd)) in
+    let instr_jalxx = instr_jal in
+    (* instruction : jr/jalr/jer/jner/jltr/jler/jltru/ljeru *)
+    let instr_jxxr = exec ^& eq_c 4 (i_i % (1, 4)) 0b0101 in
+    let f0 = i_i ** 0 in
+    let instr_jr = (not f0) ^& (eq_c 2 i_f 0) in
+    let instr_jalr = (not f0) ^& (eq_c 2 i_f 1) in
+    let instr_jalxx = instr_jalxx ^| (instr_jxxr ^& instr_jalr) in
+    let cond_jxxr = instr_jxxr ^& (alu_comparer 16 f0 i_f v_ra v_rb ^| instr_jr ^| instr_jalr) in
+    let next_pc = mux cond_jxxr next_pc v_r in
+    
+    (* prologue for jal/jalr *)
+    let wr = mux instr_jalxx wr (const "011") in
+    let rwd = mux instr_jalxx rwd next_pc in
 
     save_cpu_regs wr rwd ^.
     save_ram_read (cpu_ram ra we wa d) ^.
diff --git a/sched/simplify.ml b/sched/simplify.ml
index 37e4539..c0cd07e 100644
--- a/sched/simplify.ml
+++ b/sched/simplify.ml
@@ -136,6 +136,14 @@ let arith_simplify p =
       | Ebinop(Xor, Aconst([|false|]), x) -> Earg(x)
       | Ebinop(Xor, x, Aconst([|false|])) -> Earg(x)
 
+      | Ebinop(Nand, Avar(a), Avar(b)) when a = b ->
+        Enot(Avar(a))
+      | Ebinop(Xor, Avar(a), Avar(b)) when a = b ->
+        let sz = Env.find a p.p_vars in
+        Earg(Aconst(Array.make sz false))
+      | Ebinop(_, Avar(a), Avar(b)) when a = b ->
+        Earg(Avar(a))
+
       | Eslice(i, j, k) when i = j -> Eselect(i, k)
 
       | Econcat(Aconst(a), Aconst(b)) ->
-- 
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