nir/loop_analyze: Bail if we encounter swizzles

None of the current code knows what to do with swizzles.  Take the safe
option for now and bail if we see one.  This does have a small shader-db
impact but it is at least safe.

Shader-db results on Kaby Lake:

    total loops in shared programs: 4364 -> 4388 (0.55%)
    loops in affected programs: 5 -> 29 (480.00%)
    helped: 5
    HURT: 29

Shader-db results on Haswell:

    total loops in shared programs: 4373 -> 4370 (-0.07%)
    loops in affected programs: 5 -> 2 (-60.00%)
    helped: 5
    HURT: 2

Fixes: 6772a17acc "nir: Add a loop analysis pass"
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>

src/compiler/nir/nir_loop_analyze.c

@@ -320,6 +320,12 @@ compute_induction_information(loop_info_state *state)
       if (!is_var_phi(var))
          continue;
 
+      /* We only handle scalars because none of the rest of the loop analysis
+       * code can properly handle swizzles.
+       */
+      if (var->def->num_components > 1)
+         continue;
+
       nir_phi_instr *phi = nir_instr_as_phi(var->def->parent_instr);
       nir_basic_induction_var *biv = rzalloc(state, nir_basic_induction_var);
 
@@ -358,7 +364,9 @@ compute_induction_information(loop_info_state *state)
                for (unsigned i = 0; i < 2; i++) {
                   /* Is one of the operands const, and the other the phi */
                   if (alu->src[i].src.ssa->parent_instr->type == nir_instr_type_load_const &&
+                      alu->src[i].swizzle[0] == 0 &&
                       alu->src[1-i].src.ssa == &phi->dest.ssa)
+                     assert(alu->src[1-i].swizzle[0] == 0);
                      biv->invariant = get_loop_var(alu->src[i].src.ssa, state);
                }
             }
@@ -557,6 +565,10 @@ try_find_limit_of_alu(nir_loop_variable *limit, nir_const_value *limit_val,
 
    if (limit_alu->op == nir_op_imin ||
        limit_alu->op == nir_op_fmin) {
+      /* We don't handle swizzles here */
+      if (limit_alu->src[0].swizzle[0] > 0 || limit_alu->src[1].swizzle[0] > 0)
+         return false;
+
       limit = get_loop_var(limit_alu->src[0].src.ssa, state);
 
       if (!is_var_constant(limit))
@@ -828,10 +840,16 @@ try_find_trip_count_vars_in_iand(nir_alu_instr **alu,
    assert((*alu)->op == nir_op_ieq || (*alu)->op == nir_op_inot);
 
    nir_ssa_def *iand_def = (*alu)->src[0].src.ssa;
+   /* This is used directly in an if condition so it must be a scalar */
+   assert(iand_def->num_components == 1);
 
    if ((*alu)->op == nir_op_ieq) {
       nir_ssa_def *zero_def = (*alu)->src[1].src.ssa;
 
+      /* We don't handle swizzles here */
+      if ((*alu)->src[0].swizzle[0] > 0 || (*alu)->src[1].swizzle[0] > 0)
+         return;
+
       if (iand_def->parent_instr->type != nir_instr_type_alu ||
           zero_def->parent_instr->type != nir_instr_type_load_const) {
 
@@ -858,6 +876,10 @@ try_find_trip_count_vars_in_iand(nir_alu_instr **alu,
    if (iand->op != nir_op_iand)
       return;
 
+   /* We don't handle swizzles here */
+   if ((*alu)->src[0].swizzle[0] > 0 || (*alu)->src[1].swizzle[0] > 0)
+      return;
+
    /* Check if iand src is a terminator condition and try get induction var
     * and trip limit var.
     */