Hi
Here is a patch to inform a programmer about the expanded vector operation.
Bootstrapped on x86-unknown-linux-gnu.
ChangeLog:
* gcc/tree-vect-generic.c (expand_vector_piecewise): Adjust to
produce the warning.
(expand_vector_parallel): Adjust to produce the warning.
(lower_vec_shuffle): Adjust to produce the warning.
* gcc/common.opt: New warning Wvector-operation-expanded.
* gcc/doc/invoke.texi: Document the wawning.
Ok?
Thanks,
Artem Shinkarov.
P.S. It is hard to write a reasonable testcase for the patch, because
one needs to guess which architecture would expand a given vector
operation. But the patch is trivial.
Index: gcc/tree-vect-generic.c
===================================================================
--- gcc/tree-vect-generic.c (revision 179464)
+++ gcc/tree-vect-generic.c (working copy)
@@ -235,6 +235,10 @@ expand_vector_piecewise (gimple_stmt_ite
int delta = tree_low_cst (part_width, 1)
/ tree_low_cst (TYPE_SIZE (TREE_TYPE (type)), 1);
int i;
+ location_t loc = gimple_location (gsi_stmt (*gsi));
+
+ warning_at (loc, OPT_Wvector_operation_expanded,
+ "vector operation will be expanded piecewise");
v = VEC_alloc(constructor_elt, gc, (nunits + delta - 1) / delta);
for (i = 0; i < nunits;
@@ -260,6 +264,10 @@ expand_vector_parallel (gimple_stmt_iter
tree result, compute_type;
enum machine_mode mode;
int n_words = tree_low_cst (TYPE_SIZE_UNIT (type), 1) / UNITS_PER_WORD;
+ location_t loc = gimple_location (gsi_stmt (*gsi));
+
+ warning_at (loc, OPT_Wvector_operation_expanded,
+ "vector operation will be expanded in parallel");
/* We have three strategies. If the type is already correct, just do
the operation an element at a time. Else, if the vector is wider than
@@ -301,16 +309,15 @@ expand_vector_addition (gimple_stmt_iter
{
int parts_per_word = UNITS_PER_WORD
/ tree_low_cst (TYPE_SIZE_UNIT (TREE_TYPE (type)), 1);
+ location_t loc = gimple_location (gsi_stmt (*gsi));
if (INTEGRAL_TYPE_P (TREE_TYPE (type))
&& parts_per_word >= 4
&& TYPE_VECTOR_SUBPARTS (type) >= 4)
- return expand_vector_parallel (gsi, f_parallel,
- type, a, b, code);
+ return expand_vector_parallel (gsi, f_parallel, type, a, b, code);
else
- return expand_vector_piecewise (gsi, f,
- type, TREE_TYPE (type),
- a, b, code);
+ return expand_vector_piecewise (gsi, f, type,
+ TREE_TYPE (type), a, b, code);
}
/* Check if vector VEC consists of all the equal elements and
@@ -400,8 +407,8 @@ expand_vector_operation (gimple_stmt_ite
case PLUS_EXPR:
case MINUS_EXPR:
if (!TYPE_OVERFLOW_TRAPS (type))
- return expand_vector_addition (gsi, do_binop, do_plus_minus, type,
- gimple_assign_rhs1 (assign),
+ return expand_vector_addition (gsi, do_binop, do_plus_minus, type,
+ gimple_assign_rhs1 (assign),
gimple_assign_rhs2 (assign), code);
break;
@@ -622,6 +629,8 @@ lower_vec_shuffle (gimple_stmt_iterator
return true;
}
+ warning_at (loc, OPT_Wvector_operation_expanded,
+ "vector shuffling operation will be expanded piecewise");
if (operand_equal_p (vec0, vec1, 0))
{
unsigned i;
Index: gcc/common.opt
===================================================================
--- gcc/common.opt (revision 179464)
+++ gcc/common.opt (working copy)
@@ -694,6 +694,10 @@ Wcoverage-mismatch
Common Var(warn_coverage_mismatch) Init(1) Warning
Warn in case profiles in -fprofile-use do not match
+Wvector-operation-expanded
+Common Var(warn_vector_operation_expanded) Warning
+Warn when a vector operation is expanded piecewise
+
Xassembler
Driver Separate
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi (revision 179464)
+++ gcc/doc/invoke.texi (working copy)
@@ -271,7 +271,8 @@ Objective-C and Objective-C++ Dialects}.
-Wunused-label -Wunused-local-typedefs -Wunused-parameter @gol
-Wno-unused-result -Wunused-value @gol -Wunused-variable @gol
-Wunused-but-set-parameter -Wunused-but-set-variable @gol
--Wvariadic-macros -Wvla -Wvolatile-register-var -Wwrite-strings}
+-Wvariadic-macros -Wvector-operation-expanded -Wvla
+-Wvolatile-register-var -Wwrite-strings}
@item C and Objective-C-only Warning Options
@gccoptlist{-Wbad-function-cast -Wmissing-declarations @gol
@@ -4532,6 +4533,12 @@ Warn if variadic macros are used in peda
alternate syntax when in pedantic ISO C99 mode. This is default.
To inhibit the warning messages, use @option{-Wno-variadic-macros}.
+@item -Wvector-operation-expanded
+@opindex Wvector-operation-expanded
+@opindex Wno-vector-operation-expanded
+Warn if vector operation is not implemented via SIMD capabilities of the
+architecture. Mainly useful for the performance tuning.
+
@item -Wvla
@opindex Wvla
@opindex Wno-vla
