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cp-gimplify.c (simple_empty_class_p): New.
* cp-gimplify.c (simple_empty_class_p): New. * cp-gimplify.c (cp_gimplify_expr): Handle RETURN_EXPR. Abstract the code for empty class copies into simple_empty_class_p, and adapt it to handle COMPOUND_EXPRs. From-SVN: r221347
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Aldy Hernandez
Aldy Hernandez
parent
6b98fab5f1
commit
25de0a29fb
@ -1,3 +1,10 @@
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2015-03-11 Aldy Hernandez <aldyh@redhat.com>
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* cp-gimplify.c (simple_empty_class_p): New.
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* cp-gimplify.c (cp_gimplify_expr): Handle RETURN_EXPR. Abstract
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the code for empty class copies into simple_empty_class_p, and
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adapt it to handle COMPOUND_EXPRs.
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2015-03-10 Paolo Carlini <paolo.carlini@oracle.com>
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PR c++/65370
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@ -53,6 +53,8 @@ along with GCC; see the file COPYING3. If not see
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#include "target.h"
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#include "c-family/c-ubsan.h"
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#include "cilk.h"
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#include "gimplify.h"
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#include "gimple-expr.h"
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/* Forward declarations. */
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@ -528,6 +530,29 @@ gimplify_must_not_throw_expr (tree *expr_p, gimple_seq *pre_p)
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return GS_ALL_DONE;
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}
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/* Return TRUE if an operand (OP) of a given TYPE being copied is
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really just an empty class copy.
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Check that the operand has a simple form so that TARGET_EXPRs and
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non-empty CONSTRUCTORs get reduced properly, and we leave the
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return slot optimization alone because it isn't a copy. */
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static bool
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simple_empty_class_p (tree type, tree op)
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{
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return
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((TREE_CODE (op) == COMPOUND_EXPR
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&& simple_empty_class_p (type, TREE_OPERAND (op, 1)))
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|| is_gimple_lvalue (op)
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|| INDIRECT_REF_P (op)
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|| (TREE_CODE (op) == CONSTRUCTOR
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&& CONSTRUCTOR_NELTS (op) == 0
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&& !TREE_CLOBBER_P (op))
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|| (TREE_CODE (op) == CALL_EXPR
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&& !CALL_EXPR_RETURN_SLOT_OPT (op)))
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&& is_really_empty_class (type);
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}
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/* Do C++-specific gimplification. Args are as for gimplify_expr. */
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int
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@ -597,6 +622,7 @@ cp_gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p)
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return GS_OK;
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/* Otherwise fall through. */
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case MODIFY_EXPR:
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modify_expr_case:
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{
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if (fn_contains_cilk_spawn_p (cfun)
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&& cilk_detect_spawn_and_unwrap (expr_p)
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@ -616,31 +642,22 @@ cp_gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p)
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TREE_OPERAND (*expr_p, 1) = build1 (VIEW_CONVERT_EXPR,
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TREE_TYPE (op0), op1);
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else if ((is_gimple_lvalue (op1) || INDIRECT_REF_P (op1)
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|| (TREE_CODE (op1) == CONSTRUCTOR
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&& CONSTRUCTOR_NELTS (op1) == 0
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&& !TREE_CLOBBER_P (op1))
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|| (TREE_CODE (op1) == CALL_EXPR
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&& !CALL_EXPR_RETURN_SLOT_OPT (op1)))
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&& is_really_empty_class (TREE_TYPE (op0)))
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else if (simple_empty_class_p (TREE_TYPE (op0), op1))
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{
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/* Remove any copies of empty classes. We check that the RHS
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has a simple form so that TARGET_EXPRs and non-empty
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CONSTRUCTORs get reduced properly, and we leave the return
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slot optimization alone because it isn't a copy (FIXME so it
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shouldn't be represented as one).
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/* Remove any copies of empty classes. Also drop volatile
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variables on the RHS to avoid infinite recursion from
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gimplify_expr trying to load the value. */
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gimplify_expr (&TREE_OPERAND (*expr_p, 0), pre_p, post_p,
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is_gimple_lvalue, fb_lvalue);
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if (TREE_SIDE_EFFECTS (op1))
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{
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if (TREE_THIS_VOLATILE (op1)
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&& (REFERENCE_CLASS_P (op1) || DECL_P (op1)))
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op1 = build_fold_addr_expr (op1);
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Also drop volatile variables on the RHS to avoid infinite
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recursion from gimplify_expr trying to load the value. */
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if (!TREE_SIDE_EFFECTS (op1))
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*expr_p = op0;
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else if (TREE_THIS_VOLATILE (op1)
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&& (REFERENCE_CLASS_P (op1) || DECL_P (op1)))
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*expr_p = build2 (COMPOUND_EXPR, TREE_TYPE (*expr_p),
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build_fold_addr_expr (op1), op0);
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else
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*expr_p = build2 (COMPOUND_EXPR, TREE_TYPE (*expr_p),
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op0, op1);
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gimplify_and_add (op1, pre_p);
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}
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*expr_p = TREE_OPERAND (*expr_p, 0);
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}
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}
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ret = GS_OK;
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@ -740,6 +757,19 @@ cp_gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p)
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}
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break;
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case RETURN_EXPR:
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if (TREE_OPERAND (*expr_p, 0)
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&& (TREE_CODE (TREE_OPERAND (*expr_p, 0)) == INIT_EXPR
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|| TREE_CODE (TREE_OPERAND (*expr_p, 0)) == MODIFY_EXPR))
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{
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expr_p = &TREE_OPERAND (*expr_p, 0);
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code = TREE_CODE (*expr_p);
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/* Avoid going through the INIT_EXPR case, which can
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degrade INIT_EXPRs into AGGR_INIT_EXPRs. */
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goto modify_expr_case;
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}
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/* Fall through. */
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default:
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ret = (enum gimplify_status) c_gimplify_expr (expr_p, pre_p, post_p);
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break;
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17
gcc/testsuite/g++.dg/other/empty-class.C
Normal file
17
gcc/testsuite/g++.dg/other/empty-class.C
Normal file
@ -0,0 +1,17 @@
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/* { dg-do compile } */
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/* { dg-options "-fdump-tree-gimple" } */
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/* Test that we return retval directly, instead of going through an
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intermediate temporary, when returning an empty class. */
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class obj {
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public:
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obj(int);
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};
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obj funky(){
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return obj(555);
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}
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/* { dg-final { scan-tree-dump-times "return <retval>;" 1 "gimple" } } */
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/* { dg-final { cleanup-tree-dump "gimple" } } */
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