From 595f8a9db4a533377fdef320a146c0f85662eefa Mon Sep 17 00:00:00 2001
From: Enrico Lumetti <enrico.lumetti@gmail.com>
Date: Wed, 5 May 2021 20:55:32 +0200
Subject: [PATCH] Add select-instructions pass

---
 select-instructions.rkt      | 65 +++++++++++++++++++++++++++++++++
 test-select-instructions.rkt | 71 ++++++++++++++++++++++++++++++++++++
 2 files changed, 136 insertions(+)
 create mode 100644 select-instructions.rkt
 create mode 100644 test-select-instructions.rkt

diff --git a/select-instructions.rkt b/select-instructions.rkt
new file mode 100644
index 0000000..b7c6529
--- /dev/null
+++ b/select-instructions.rkt
@@ -0,0 +1,65 @@
+#lang racket
+
+(require racket/list)
+
+(provide select-instructions)
+
+(define (select-instructions p)
+  (match p
+    [`(program ,data ,body) `(AArch64VProgram ,data ,(select-instructions-section (car body)))]))
+
+(define (select-instructions-section sec)
+  (match sec
+    [`(,label . ,statement) `(,label . (Block `() ,(select-instructions-stmt statement)))]))
+
+(define (select-instructions-stmt stmt)
+  (match stmt
+    [`(return ,exp) (select-instructions-return exp)]
+    [`(seq (assign ,var ,exp) ,next-stmt) 
+      (append (select-instructions-assign var exp) 
+              (select-instructions-stmt next-stmt))]))
+
+(define (select-instructions-assign var exp)
+  (match exp
+         [(? symbol?) (list `(Instr mov ((Var ,var) (Var ,exp))))]
+         [(? fixnum?) (list `(Instr mov ((Var ,var) (Imm ,exp))))]
+         [`(read)     (select-instructions-read `(Var ,var))]
+         [`(- ,e)     (select-instructions-neg e `(Var ,var))]
+         [`(+ ,a ,b)  (select-instructions-add a b `(Var ,var))]))
+
+(define (select-instructions-return exp)
+  (append (match exp
+                [(? symbol?) (list `(Instr mov (x0 (Var ,exp))))]
+                [(? fixnum?) (list `(Instr mov (x0 (Imm ,exp))))]
+                [`(read)     (select-instructions-read 'x0)]
+                [`(- ,e)     (select-instructions-neg e 'x0)]
+                [`(+ ,a ,b)  (select-instructions-add a b 'x0)])
+          `[(Instr b (conclusion))]))
+
+(define (select-instructions-read dest)
+  (if (eq? dest 'x0)
+      (list `(Instr bl _builtin_read))
+      (list `(Instr bl _builtin_read) `(Instr mov (,dest x0)))))
+
+(define (select-instructions-neg exp dest)
+  (begin
+    (define var-exp (if (fixnum? exp)
+                        `(Imm ,exp)
+                        `(Var ,exp)))
+    (list `(Instr neg (,dest ,var-exp)))))
+
+(define (select-instructions-add a b dest)
+  (begin
+    ; if e1 is an imm, swap
+    (define-values (e1 e2) (imm-to-right a b))
+    (define num-imm (count fixnum? (list e1 e2)))
+    (match num-imm
+           [0 (list `(Instr add (,dest (Var ,e1) (Var ,e2))))]
+           [1 (list `(Instr add (,dest (Var ,e1) (Imm ,e2))))]
+           [2 (list `(Instr mov (,dest (Imm ,e1)))
+                    `(Instr add (,dest ,dest (Imm ,e2))))])))
+           
+(define (imm-to-right e1 e2)
+  (if (and (fixnum? e1) (not (fixnum? e2)))
+      (values e2 e1)
+      (values e1 e2)))
diff --git a/test-select-instructions.rkt b/test-select-instructions.rkt
new file mode 100644
index 0000000..22a7b15
--- /dev/null
+++ b/test-select-instructions.rkt
@@ -0,0 +1,71 @@
+#lang racket
+
+(require "select-instructions.rkt")
+(require "test-util.rkt")
+
+(define programs
+    (list
+      `(program ()
+          ((start .
+            (return (+ 2 3)))))
+      `(program ()
+          ((start .
+            (seq (assign x 3)
+              (return (+ 2 x))))))
+      `(program ()
+          ((start .
+             (seq (assign tmp.1 (read))
+               (return (+ tmp.1 3))))))
+      `(program ()
+                ((start .
+                  (seq (assign tmp.1 (- 1))
+                       (seq (assign x.1 (+ tmp.1 2))
+                            (seq (assign tmp.2 (+ x.1 2))
+                                 (seq (assign tmp.3 (+ 4 5))
+                                      (return (+ tmp.2 tmp.3)))))))))))
+
+
+(test-eq (select-instructions (list-ref programs 0))
+         `(AArch64VProgram
+           ()
+           (start
+            Block
+            `()
+            ((Instr mov (x0 (Imm 2)))
+             (Instr add (x0 x0 (Imm 3)))
+             (Instr b (conclusion))))))
+
+(test-eq (select-instructions (list-ref programs 1))
+         `(AArch64VProgram
+           ()
+           (start
+            Block
+            `()
+            ((Instr mov ((Var x) (Imm 3)))
+             (Instr add (x0 (Var x) (Imm 2)))
+             (Instr b (conclusion))))))
+
+(test-eq (select-instructions (list-ref programs 2))
+         `(AArch64VProgram
+           ()
+           (start
+            Block
+            `()
+            ((Instr bl _builtin_read)
+             (Instr mov ((Var tmp.1) x0))
+             (Instr add (x0 (Var tmp.1) (Imm 3)))
+             (Instr b (conclusion))))))
+
+(test-eq (select-instructions (list-ref programs 3))
+         `(AArch64VProgram
+           ()
+           (start
+            Block
+            `()
+            ((Instr neg ((Var tmp.1) (Imm 1)))
+             (Instr add ((Var x.1) (Var tmp.1) (Imm 2)))
+             (Instr add ((Var tmp.2) (Var x.1) (Imm 2)))
+             (Instr mov ((Var tmp.3) (Imm 4)))
+             (Instr add ((Var tmp.3) (Var tmp.3) (Imm 5)))
+             (Instr add (x0 (Var tmp.2) (Var tmp.3)))
+             (Instr b (conclusion))))))