x87: Only use fucompp if one operand happens to be at st(1).

[libfirm] / ir / be / ia32 / ia32_x87.c

diff --git a/ir/be/ia32/ia32_x87.c b/ir/be/ia32/ia32_x87.c
index 58a3391..82bc54d 100644 (file)
--- a/ir/be/ia32/ia32_x87.c
+++ b/ir/be/ia32/ia32_x87.c
@@ -1223,60 +1223,19 @@ static int sim_Fucom(x87_state *state, ir_node *n)
                                        }
                                        /* res = tos X op, pop */
                                        pops    = 1;
-                               }
-                               /* different, move them to st and st(1) and pop both.
-                                  The tricky part is to get one into st(1).*/
-                               else if (op2_idx == 1) {
-                                       /* good, second operand is already in the right place, move the first */
-                                       if (op1_idx != 0) {
-                                               /* bring the first on top */
-                                               x87_create_fxch(state, n, op1_idx);
-                                               assert(op2_idx != 0);
-                                               op1_idx = 0;
-                                       }
-                                       /* res = tos X op, pop, pop */
-                                       pops = 2;
-                               } else if (op1_idx == 1) {
-                                       /* good, first operand is already in the right place, move the second */
-                                       if (op2_idx != 0) {
-                                               /* bring the first on top */
-                                               x87_create_fxch(state, n, op2_idx);
-                                               assert(op1_idx != 0);
-                                               op2_idx = 0;
-                                       }
-                                       /* res = op X tos, pop, pop */
-                                       pops = 2;
                                } else {
-                                       /* if one is already the TOS, we need two fxch */
-                                       if (op1_idx == 0) {
-                                               /* first one is TOS, move to st(1) */
-                                               x87_create_fxch(state, n, 1);
-                                               assert(op2_idx != 1);
-                                               op1_idx = 1;
-                                               x87_create_fxch(state, n, op2_idx);
-                                               op2_idx = 0;
-                                               /* res = op X tos, pop, pop */
-                                               pops    = 2;
-                                       } else if (op2_idx == 0) {
-                                               /* second one is TOS, move to st(1) */
-                                               x87_create_fxch(state, n, 1);
-                                               assert(op1_idx != 1);
-                                               op2_idx = 1;
-                                               x87_create_fxch(state, n, op1_idx);
-                                               op1_idx = 0;
-                                               /* res = tos X op, pop, pop */
-                                               pops    = 2;
-                                       } else {
-                                               /* none of them is either TOS or st(1), 3 fxch needed */
-                                               x87_create_fxch(state, n, op2_idx);
-                                               assert(op1_idx != 0);
-                                               x87_create_fxch(state, n, 1);
-                                               op2_idx = 1;
-                                               x87_create_fxch(state, n, op1_idx);
-                                               op1_idx = 0;
-                                               /* res = tos X op, pop, pop */
-                                               pops    = 2;
+                                       if (op1_idx != 0 && op2_idx != 0) {
+                                               /* Both not at tos: Move one operand to tos. Move the one not at
+                                                * pos 1, so we get a chance to use fucompp. */
+                                               if (op1_idx != 1) {
+                                                       x87_create_fxch(state, n, op1_idx);
+                                                       op1_idx = 0;
+                                               } else {
+                                                       x87_create_fxch(state, n, op2_idx);
+                                                       op2_idx = 0;
+                                               }
                                        }
+                                       pops = 2;
                                }
                        }
                }
@@ -1295,15 +1254,23 @@ static int sim_Fucom(x87_state *state, ir_node *n)
 
        /* patch the operation */
        if (is_ia32_vFucomFnstsw(n)) {
-               dst = pops == 2 ? op_ia32_FucomppFnstsw : op_ia32_FucomFnstsw;
-               for (int i = 0; i < pops; ++i)
+               if (pops == 2 && (op1_idx == 1 || op2_idx == 1)) {
+                       dst = op_ia32_FucomppFnstsw;
                        x87_pop(state);
+                       x87_pop(state);
+               } else {
+                       dst = op_ia32_FucomFnstsw;
+                       goto pop;
+               }
        } else if (is_ia32_vFucomi(n)) {
                dst = op_ia32_Fucomi;
+pop:
                if (pops != 0)
                        x87_pop(state);
-               if (pops == 2)
-                       x87_create_fpop(state, sched_next(n), 0);
+               if (pops == 2) {
+                       int const idx = (op1_idx != 0 ? op1_idx : op2_idx) - 1 /* Due to prior pop. */;
+                       x87_create_fpop(state, sched_next(n), idx);
+               }
        } else {
                panic("invalid operation %+F", n);
        }