[Bug middle-end/59471] [4.9 Regression] ICE using vector extensions (non-top-level BIT_FIELD_REF, IMAGPART_EXPR or REALPART_EXPR)

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59471

--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
Testing

Index: gimplify.c                                                               
===================================================================             
--- gimplify.c  (revision 205891)                                               
+++ gimplify.c  (working copy)                                                  
@@ -7358,12 +7358,22 @@ gimplify_expr (tree *expr_p, gimple_seq                 
                                        TREE_TYPE (*expr_p));                   
          break;                                                                

+       case VIEW_CONVERT_EXPR:                                                 
+         if (is_gimple_reg_type (TREE_TYPE (*expr_p))                          
+             && is_gimple_reg_type (TREE_TYPE (TREE_OPERAND (*expr_p, 0))))    
+           {                                                                   
+             ret = gimplify_expr (&TREE_OPERAND (*expr_p, 0), pre_p,           
+                                  post_p, is_gimple_val, fb_rvalue);           
+             recalculate_side_effects (*expr_p);                               
+             break;                                                            
+           }                                                                   
+         /* Fallthru.  */                                                      
+                                                                               
        case ARRAY_REF:                                                         
        case ARRAY_RANGE_REF:                                                   
        case REALPART_EXPR:                                                     
        case IMAGPART_EXPR:                                                     
        case COMPONENT_REF:                                                     
-       case VIEW_CONVERT_EXPR:                                                 
          ret = gimplify_compound_lval (expr_p, pre_p, post_p,                  
                                        fallback ? fallback : fb_rvalue);       
          break;                                                                
@@ -7709,10 +7719,17 @@ gimplify_expr (tree *expr_p, gimple_seq                 
          break;                                                                

        case BIT_FIELD_REF:                                                     
-         ret = gimplify_expr (&TREE_OPERAND (*expr_p, 0), pre_p,               
-                              post_p, is_gimple_lvalue, fb_either);            
-         recalculate_side_effects (*expr_p);                                   
-         break;                                                                
+         {                                                                     
+           if (is_gimple_reg_type (TREE_TYPE (*expr_p))                        
+               && is_gimple_reg_type (TREE_TYPE (TREE_OPERAND (*expr_p, 0))))  
+             ret = gimplify_expr (&TREE_OPERAND (*expr_p, 0), pre_p,           
+                                  post_p, is_gimple_val, fb_rvalue);           
+           else                                                                
+             ret = gimplify_expr (&TREE_OPERAND (*expr_p, 0), pre_p,           
+                                  post_p, is_gimple_lvalue, fb_either);        
+           recalculate_side_effects (*expr_p);                                 
+           break;                                                              
+         }                                                                     

        case TARGET_MEM_REF:                                                    
          {                                                      


code-generation for the testcase is awkward though:

foo:
.LFB0:  
        .cfi_startproc
        movaps  %xmm0, -24(%rsp)
        movq    -24(%rsp), %rax
        movq    %rax, -24(%rsp)
        movq    -24(%rsp), %xmm0
        ret

not sure why RTL cannot recover here, we expand from

foo (uint16x8_t x)
{
  vector(2) long unsigned int _2;
  long unsigned int _3;
  uint8x8_t _4;

  <bb 2>:
  _2 = VIEW_CONVERT_EXPR<vector(2) long unsigned int>(x_5(D));
  _3 = BIT_FIELD_REF <_2, 64, 0>;
  _4 = VIEW_CONVERT_EXPR<uint8x8_t>(_3);
  return _4;

with forwprop we could re-write this into

  _4 = BIT_FIELD_REF <x_5(D), 64, 0>;

as BIT_FIELD_REF is allowed to select uint8x8_t from uint16x8_t directly.