8 shift bug

R=ken
OCL=32882
CL=32882

diff --git a/src/cmd/8g/ggen.c b/src/cmd/8g/ggen.c
index 3542ae6909bb15f4a2ba92b23b82c37cff7ed219..362e649d03382bb22e1cc8ef68e00223cd8a8105 100644 (file)
--- a/src/cmd/8g/ggen.c
+++ b/src/cmd/8g/ggen.c
@@ -499,6 +499,18 @@ ret:
        ;
 }
 
+int
+samereg(Node *a, Node *b)
+{
+       if(a->op != OREGISTER)
+               return 0;
+       if(b->op != OREGISTER)
+               return 0;
+       if(a->val.u.reg != b->val.u.reg)
+               return 0;
+       return 1;
+}
+
 /*
  * generate division.
  * caller must set:
@@ -581,7 +593,7 @@ cgen_div(int op, Node *nl, Node *nr, Node *res)
 void
 cgen_shift(int op, Node *nl, Node *nr, Node *res)
 {
-       Node n1, n2;
+       Node n1, n2, cx, oldcx;
        int a, w;
        Prog *p1;
        uvlong sc;
@@ -611,10 +623,20 @@ cgen_shift(int op, Node *nl, Node *nr, Node *res)
                return;
        }
 
+       memset(&oldcx, 0, sizeof oldcx);
+       nodreg(&cx, types[TUINT32], D_CX);
+       if(reg[D_CX] > 0 && !samereg(&cx, res)) {
+               regalloc(&oldcx, types[TUINT32], N);
+               gmove(&cx, &oldcx);
+       }
+
        nodreg(&n1, types[TUINT32], D_CX);
        regalloc(&n1, nr->type, &n1);           // to hold the shift type in CX
 
-       regalloc(&n2, nl->type, res);
+       if(samereg(&cx, res))
+               regalloc(&n2, nl->type, N);
+       else
+               regalloc(&n2, nl->type, res);
        if(nl->ullman >= nr->ullman) {
                cgen(nl, &n2);
                cgen(nr, &n1);
@@ -633,6 +655,11 @@ cgen_shift(int op, Node *nl, Node *nr, Node *res)
        }
        patch(p1, pc);
        gins(a, &n1, &n2);
+       
+       if(oldcx.op != 0) {
+               gmove(&oldcx, &cx);
+               regfree(&oldcx);
+       }
 
        gmove(&n2, res);