shithub: mc

Download patch

ref: 6a921aa5b2045b172370c1677c1e3f75b8c3cfc4
parent: f90519332a6d24444a54c2b0943f705e8579550f
author: Ori Bernstein <ori@eigenstate.org>
date: Mon Sep 8 20:37:08 EDT 2014 

Generates 'rol' instructions.

    This doesn't seem to have the performance effect
    I was hoping for with the sha1 calculaton, but it
    still improves code gen time, since there are fewer
    dumb, wasteful instructions.


--- a/6/insns.def
+++ b/6/insns.def
@@ -92,6 +92,7 @@
     "\tIMUL%T %X,%R\n",
     Use(.l={1,2}),
     Def(.l={2}))
+
 /* there is no imul for 8 bit values. */
 Insn(Iimul_r,
     "\timul%t %r\n",
@@ -166,6 +167,16 @@
 Insn(Ishr,
     "\tshr%2t %u,%r\n",
     "\tSHR%2T %U,%R\n",
+    Use(.l={1,2}),
+    Def(.l={2}))
+Insn(Irol,
+    "\trol%2t %u,%r\n",
+    "\tROL%2T %U,%R\n",
+    Use(.l={1,2}),
+    Def(.l={2}))
+Insn(Iror,
+    "\tror%2t %u,%r\n",
+    "\tROR%2T %U,%R\n",
     Use(.l={1,2}),
     Def(.l={2}))
 
--- a/6/isel.c
+++ b/6/isel.c
@@ -593,6 +593,59 @@
     return ret;
 }
 
+static int litval(Node *n, vlong *v)
+{
+    Node *l;
+
+    if (exprop(n) != Olit)
+        return 0;
+    l = n->expr.args[0];
+    if (l->lit.littype != Lint)
+        return 0;
+    *v = l->lit.intval;
+    return 1;
+}
+
+int isrol(Isel *s, Node *l, Node *r, Loc **dist, Loc **rol)
+{
+    vlong a, b, sz;
+
+    sz = size(r)*8;
+    /* check if we have paired left/right shifts */
+    if (exprop(l) != Obsl && exprop(l) != Obsr)
+        return 0;
+    if (exprop(r) != Obsl && exprop(r) != Obsr)
+        return 0;
+    if (exprop(r) == exprop(l))
+        return 0;
+
+    /* check if we're shifting by constants */
+    if (!litval(l->expr.args[1], &a))
+        return 0;
+    if (!litval(r->expr.args[1], &b))
+        return 0;
+
+    /* and we're shifting the same variable */
+    if (exprop(l->expr.args[0]) != Ovar)
+        return 0;
+    if (exprop(r->expr.args[0]) != Ovar)
+        return 0;
+    if (l->expr.args[0]->expr.did != r->expr.args[0]->expr.did)
+        return 0;
+
+    /* and then figure out the shift amount */
+    if (a + b != sz)
+        return 0;
+    if (exprop(l) == Obsl)
+        *dist = loclit(a, mode(l));
+    else
+        *dist = loclit(sz - a, mode(l));
+    *rol = selexpr(s, l->expr.args[0]);
+    return 1;
+}
+
+
+
 Loc *selexpr(Isel *s, Node *n)
 {
     Loc *a, *b, *c, *d, *r;
@@ -608,9 +661,14 @@
     switch (exprop(n)) {
         case Oadd:      r = binop(s, Iadd, args[0], args[1]); break;
         case Osub:      r = binop(s, Isub, args[0], args[1]); break;
-        case Obor:      r = binop(s, Ior,  args[0], args[1]); break;
         case Oband:     r = binop(s, Iand, args[0], args[1]); break;
         case Obxor:     r = binop(s, Ixor, args[0], args[1]); break;
+        case Obor:
+            if (isrol(s, args[0], args[1], &d, &r))
+                g(s, Irol, d, r, NULL);
+            else
+                r = binop(s, Ior,  args[0], args[1]);
+            break;
         case Omul:
             if (size(args[0]) == 1) {
                 a = selexpr(s, args[0]);