lower alloca as a separate pass before isel

1 files changed, 37 insertions, 0 deletions

diff --git a/ir/stack.c b/ir/stack.c
new file mode 100644
index 0000000..2420fdb
--- /dev/null
+++ b/ir/stack.c
@@ -0,0 +1,37 @@
+#include "ir.h"
+
+void
+lowerstack(struct function *fn)
+{
+   extern int ninstr;
+   fn->stksiz = 0;
+   FREQUIRE(FNUSE);
+
+   struct block *blk = fn->entry;
+   do {
+      for (int i = 0; i < blk->ins.n; ++i) {
+         uint alignlog2, siz;
+         int t = blk->ins.p[i];
+         struct instr *ins = &instrtab[t];
+         switch (ins->op) {
+         case Oalloca1: case Oalloca2: case Oalloca4: case Oalloca8: case Oalloca16:
+            alignlog2 = ins->op - Oalloca1;
+            assert(ins->l.i > 0);
+            siz = ins->l.i << alignlog2;
+            fn->stksiz += siz;
+            fn->stksiz = alignup(fn->stksiz, 1 << alignlog2);
+            if (fn->stksiz > (1<<16)-1) error(NULL, "'%s' stack frame too big", fn->name);
+            *ins = mkinstr(Onop,0,);
+            replcuses(mkref(RTMP, t), mkref(RSTACK, fn->stksiz));
+            continue;
+         }
+      }
+   } while ((blk = blk->lnext) != fn->entry);
+
+   if (ccopt.dbg.s) {
+      bfmt(ccopt.dbgout, "<< After stack >>\n");
+      irdump(fn);
+   }
+}
+
+/* vim:set ts=3 sw=3 expandtab: */