From 8cea6c2e91641b06921b4e358c73c60981ba366d Mon Sep 17 00:00:00 2001
From: lemon <lsof@mailbox.org>
Date: Tue, 20 Jun 2023 19:11:15 +0200
Subject: add basic mem2reg

promotes uniform stack slots to temporaries

currently only for immutable variables, next thing to implement is ssa
construction
---
 optmem.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 optmem.c

(limited to 'optmem.c')

diff --git a/optmem.c b/optmem.c
new file mode 100644
index 0000000..ba81cd2
--- /dev/null
+++ b/optmem.c
@@ -0,0 +1,99 @@
+#include "ir.h"
+
+static const uchar loadszcls[] = {
+   [Oloads1 - Oloads1] = 1|KI4<<4, [Oloadu1 - Oloads1] = 1|KI4<<4,
+   [Oloads2 - Oloads1] = 2|KI4<<4, [Oloadu2 - Oloads1] = 2|KI4<<4,
+   [Oloads4 - Oloads1] = 4|KI4<<4, [Oloadu4 - Oloads1] = 4|KI4<<4,
+   [Oloadi8 - Oloads1] = 8|KI8<<4,
+   [Oloadf4 - Oloads1] = 4|KF4<<4,
+   [Oloadf8 - Oloads1] = 8|KF8<<4,
+};
+static const uchar load2ext[] = {
+   [Oloads1 - Oloads1] = Oexts1, [Oloadu1 - Oloads1] = Oextu1,
+   [Oloads2 - Oloads1] = Oexts2, [Oloadu2 - Oloads1] = Oextu2,
+   [Oloads4 - Oloads1] = Oexts4, [Oloadu4 - Oloads1] = Oextu4,
+   [Oloadi8 - Oloads1] = Ocopy,
+};
+#define loadsz(o) (loadszcls[(o) - Oloads1] & 0xF)
+#define loadcls(o) (loadszcls[(o) - Oloads1] >> 4)
+#define load2ext(o) (load2ext[(o) - Oloads1])
+#define storesz(o) (1 << ((o) - Ostore1))
+
+void
+mem2reg(struct function *fn)
+{
+   extern int ninstr;
+   struct uses *uses = ssauses(fn);
+   struct block *blk = fn->entry;
+
+   do {
+      for (int i = 0; i < blk->ins.n; ++i) {
+         struct use *use, *uend;
+         union ref var;
+         enum irclass k = 0;
+         int sz = 0, ndef = 0;
+         enum op ext;
+         int t = blk->ins.p[i];
+         struct instr *ins = &instrtab[t];
+         
+         if (!oisalloca(ins->op)) continue;
+         for (use = uses[t].use, uend = &uses[t].use[uses[t].nuse]; use < uend; ++use) {
+            struct instr *m;
+            
+            if (use->isjmp) goto Next;
+            m = &instrtab[use->ins];
+            if (oisload(m->op) && (!sz || sz == loadsz(m->op))) {
+               sz = loadsz(m->op);
+               k = loadcls(m->op);
+               if (sz < 4) ext = load2ext(m->op);
+               continue;
+            }
+            if (oisstore(m->op) && m->l.bits == mkref(RTMP, t).bits
+            && (!sz || sz == storesz(m->op))) {
+               sz = storesz(m->op);
+               ++ndef;
+               continue;
+            }
+            goto Next;
+         }
+         if (!ndef) /* slot is read from but never written to */
+            goto Next;
+
+         if (ndef>1) /* TODO phi construction */
+            goto Next;
+
+         /* remove alloca */
+         *ins = mkinstr(Onop, 0,);
+         
+         var.t = 0;
+         for (use = uses[t].use; use < uend; ++use) {
+            struct instr *m = &instrtab[use->ins];
+
+            if (oisstore(m->op)) {
+               if (sz < 4) {
+                  *m = mkinstr(ext, KI4, m->r);
+                  var = mkref(RTMP, use->ins);
+               } else {
+                  var = m->r;
+                  *m = mkinstr(Onop,0,);
+               }
+            } else if (oisload(m->op)) {
+               if (!var.t) /* use before def */
+                  goto Next;
+               *m = mkinstr(Ocopy, k, var);
+            }
+         }
+         
+      Next:;
+      }
+   } while ((blk = blk->lnext) != fn->entry);
+
+   freeuses(uses, ninstr);
+   if (ccopt.dbg.m) {
+      efmt("<< After mem2reg >>\n");
+      irdump(fn);
+   }
+}
+
+
+/* vim:set ts=3 sw=3 expandtab: */
-- 
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