[hackers] [scc] [cc2-qbe] Implement switch statements || Roberto E. Vargas Caballero

[git]

commit 28b4043893d831ce7209dc413e7ce43047de3da0
Author:     Roberto E. Vargas Caballero <roberto.var...@igrid-td.com>
AuthorDate: Mon Sep 26 11:41:01 2016 +0200
Commit:     Roberto E. Vargas Caballero <roberto.var...@igrid-td.com>
CommitDate: Mon Sep 26 11:41:01 2016 +0200

    [cc2-qbe] Implement switch statements
    
    This is a first implementation of switches, which uses a if-else-if
    chain. At this point we cannot implement any other form of switch
    because we need support for indirect jump in qbe.

diff --git a/cc2/arch/qbe/cgen.c b/cc2/arch/qbe/cgen.c
index 7e41be2..b3eef3c 100644
--- a/cc2/arch/qbe/cgen.c
+++ b/cc2/arch/qbe/cgen.c
@@ -414,6 +414,47 @@ function(void)
        return NULL;
 }
 
+static void
+swtch_if(Node *idx)
+{
+       Node aux1, aux2, *np;
+       Symbol *deflabel = NULL;
+
+       for (;;) {
+               np = delstmt();
+               setlabel(np->label);
+
+               switch (np->op) {
+               case OESWITCH:
+                       if (deflabel) {
+                               aux1.op = OJMP;
+                               aux1.label = NULL;
+                               aux1.u.sym = deflabel;
+                               cgen(&aux1);
+                       }
+                       return;
+               case OCASE:
+                       aux1 = *np;
+                       aux1.op = OBRANCH;
+                       aux1.label = NULL;
+                       aux1.left = &aux2;
+
+                       aux2.op = OEQ;
+                       aux2.type = idx->type;
+                       aux2.left = np->left;
+                       aux2.right = idx;
+
+                       cgen(&aux1);
+                       break;
+               case ODEFAULT:
+                       deflabel = np->u.sym;
+                       break;
+               default:
+                       abort();
+               }
+       }
+}
+
 static Node *
 rhs(Node *np, Node *ret)
 {
@@ -550,11 +591,6 @@ rhs(Node *np, Node *ret)
                return lhs(l, ret);
        case OFIELD:
                return field(np, ret, 0);
-       case OCASE:
-       case ODEFAULT:
-       case OESWITCH:
-       case OBSWITCH:
-               /* TODO: implement these operators */
        default:
                abort();
        }
@@ -586,6 +622,10 @@ cgen(Node *np)
                p = (np->left) ? rhs(np->left, &ret) : NULL;
                code(ASRET, NULL, p, NULL);
                break;
+       case OBSWITCH:
+               p = rhs(np->left, &ret);
+               swtch_if(p);
+               break;
        default:
                rhs(np, &ret);
                break;