Hi
Enable GIMPLE folding of the vec_splat() intrinsic. (v3).
This uses the tree_vec_extract() function out of tree-vect-generic.c
to retrieve the splat value, which is a BIT_FIELD_REF. That function is
made non-static as part of this change.
Testcases are already in-tree.
V2 updates, per feedback previously received.
Forced arg1 into range (modulo #elements) before attempting to extract
the splat value.
Removed the (now unnecessary) code that did bounds-checking before calling
the tree_vec_extract helper.
Used arg0_type rather than lhs_type for calculating the tree size.
V3 updates, inspired by additional offline discussion with Segher.
Noting that for vec_splat(arg1,arg2), the ABI describes ARG2 as an element
number less than the number of elements supported by the respective ARG1
type, so we do not attempt to gimple-fold the intrinsic if we determine our
value is out of range. Thus, the initial check ensures that ARG1 is both
constant and has a valid index into ARG0.
The subsequent modulo operation is no longer necessary, and has been removed.
Also eliminated a few now-unused variables.
Sniff-tests pass. full regtest against powerpc platforms is in the queue.
OK for trunk with passing test results?
Thanks,
-Will
[gcc]
2018-08-20 Will Schmidt <will_schm...@vnet.ibm.com>
* config/rs6000/rs6000.c (rs6000_gimple_fold_builtin): Add support for
early gimple folding of vec_splat().
* tree-vect-generic.c: Remove static from tree_vec_extract() definition.
* gimple-fold.h: Add an extern define for tree_vec_extract().
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 5f77afd..4c3257f 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -15768,10 +15768,52 @@ rs6000_gimple_fold_builtin (gimple_stmt_iterator *gsi)
tree splat_tree = build_vector_from_val (TREE_TYPE (lhs), splat_value);
g = gimple_build_assign (lhs, splat_tree);
gimple_set_location (g, gimple_location (stmt));
gsi_replace (gsi, g, true);
return true;
+ }
+
+ /* Flavors of vec_splat. */
+ /* a = vec_splat (b, 0x3) becomes a = { b[3],b[3],b[3],...}; */
+ case ALTIVEC_BUILTIN_VSPLTB:
+ case ALTIVEC_BUILTIN_VSPLTH:
+ case ALTIVEC_BUILTIN_VSPLTW:
+ case VSX_BUILTIN_XXSPLTD_V2DI:
+ case VSX_BUILTIN_XXSPLTD_V2DF:
+ {
+ arg0 = gimple_call_arg (stmt, 0); /* input vector. */
+ arg1 = gimple_call_arg (stmt, 1); /* index into arg0. */
+ /* Only fold the vec_splat_*() if arg1 is both a constant value, and a
valid
+ index into the arg0 vector. */
+ unsigned int n_elts = VECTOR_CST_NELTS (arg0);
+ if (TREE_CODE (arg1) != INTEGER_CST
+ || TREE_INT_CST_LOW (arg1) > (n_elts -1))
+ return false;
+ lhs = gimple_call_lhs (stmt);
+ tree lhs_type = TREE_TYPE (lhs);
+ tree arg0_type = TREE_TYPE (arg0);
+ tree splat;
+ if (TREE_CODE (arg0) == VECTOR_CST)
+ splat = VECTOR_CST_ELT (arg0, TREE_INT_CST_LOW (arg1));
+ else
+ {
+ /* Determine (in bits) the length and start location of the
+ splat value for a call to the tree_vec_extract helper. */
+ int splat_elem_size = TREE_INT_CST_LOW (size_in_bytes (arg0_type))
+ * BITS_PER_UNIT / n_elts;
+ int splat_start_bit = TREE_INT_CST_LOW (arg1) * splat_elem_size;
+ tree len = build_int_cst (bitsizetype, splat_elem_size);
+ tree start = build_int_cst (bitsizetype, splat_start_bit);
+ splat = tree_vec_extract (gsi, TREE_TYPE (lhs_type), arg0,
+ len, start);
+ }
+ /* And finally, build the new vector. */
+ tree splat_tree = build_vector_from_val (lhs_type, splat);
+ g = gimple_build_assign (lhs, splat_tree);
+ gimple_set_location (g, gimple_location (stmt));
+ gsi_replace (gsi, g, true);
+ return true;
}
/* vec_mergel (integrals). */
case ALTIVEC_BUILTIN_VMRGLH:
case ALTIVEC_BUILTIN_VMRGLW:
diff --git a/gcc/gimple-fold.h b/gcc/gimple-fold.h
index 04e9bfa..e634180 100644
--- a/gcc/gimple-fold.h
+++ b/gcc/gimple-fold.h
@@ -59,10 +59,11 @@ extern tree gimple_fold_indirect_ref (tree);
extern bool gimple_fold_builtin_sprintf (gimple_stmt_iterator *);
extern bool gimple_fold_builtin_snprintf (gimple_stmt_iterator *);
extern bool arith_code_with_undefined_signed_overflow (tree_code);
extern gimple_seq rewrite_to_defined_overflow (gimple *);
extern void replace_call_with_value (gimple_stmt_iterator *, tree);
+extern tree tree_vec_extract (gimple_stmt_iterator *, tree, tree, tree, tree);
/* gimple_build, functionally matching fold_buildN, outputs stmts
int the provided sequence, matching and simplifying them on-the-fly.
Supposed to replace force_gimple_operand (fold_buildN (...), ...). */
extern tree gimple_build (gimple_seq *, location_t,
diff --git a/gcc/tree-vect-generic.c b/gcc/tree-vect-generic.c
index 909f790..1c9701d 100644
--- a/gcc/tree-vect-generic.c
+++ b/gcc/tree-vect-generic.c
@@ -118,11 +118,11 @@ build_word_mode_vector_type (int nunits)
typedef tree (*elem_op_func) (gimple_stmt_iterator *,
tree, tree, tree, tree, tree, enum tree_code,
tree);
-static inline tree
+tree
tree_vec_extract (gimple_stmt_iterator *gsi, tree type,
tree t, tree bitsize, tree bitpos)
{
if (TREE_CODE (t) == SSA_NAME)
{
