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| author | Roger Sayle <roger@nextmovesoftware.com> | 2021-08-20 00:24:23 +0100 |
|---|---|---|
| committer | Roger Sayle <roger@nextmovesoftware.com> | 2021-08-20 00:28:47 +0100 |
| commit | 976401aa4781fa5850e1f34142bc13d1cfe0b2bd (patch) | |
| tree | 799b32089cf1082f197598a9ac10b6e475d7aee2 | |
| parent | b0963c4379becafaebd8e52b0b42698ff151c293 (diff) | |
| download | gcc-976401aa4781fa5850e1f34142bc13d1cfe0b2bd.zip gcc-976401aa4781fa5850e1f34142bc13d1cfe0b2bd.tar.gz gcc-976401aa4781fa5850e1f34142bc13d1cfe0b2bd.tar.bz2 | |
Fold more constants during veclower pass.
An issue with a backend patch I've been investigating has revealed
a missed optimization opportunity during GCC's vector lowering pass.
An unrecognized insn for "(set (reg:SI) (not:SI (const_int 0))"
revealed that not only was my expander not expecting a NOT with
a constant operand, but also that veclower was producing the
dubious tree expression ~0.
The attached patch replaces a call to gimple_build_assign with a
call to either gimplify_build1 or gimplify_build2 depending upon
whether the operation takes one or two operands. The net effect
is that where GCC previously produced the following optimized
gimple for testsuite/c-c++common/Wunused-var-16.c (notice the ~0
and the "& 0"):
void foo ()
{
V x;
V y;
vector(16) unsigned char _1;
unsigned char _7;
unsigned char _8;
y_2 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
x_3 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
_7 = ~0;
_1 = {_7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7};
_8 = 0 & _7;
y_4 = {_8, _8, _8, _8, _8, _8, _8, _8, _8, _8, _8, _8, _8, _8, _8, _8};
v = y_4;
return;
}
With this patch we now generate:
void foo ()
{
V x;
V y;
vector(16) unsigned char _1;
y_2 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
x_3 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
_1 = { 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 2
55, 255 };
y_4 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
v = y_4;
return;
}
2021-08-20 Roger Sayle <roger@nextmovesoftware.com>
gcc/ChangeLog
* tree-vect-generic.c (expand_vector_operations_1): Use either
gimplify_build1 or gimplify_build2 instead of gimple_build_assign
when constructing scalar splat expressions.
gcc/testsuite/ChangeLog
* c-c++-common/Wunused-var-16.c: Add an extra check that ~0
is optimized away.
| -rw-r--r-- | gcc/testsuite/c-c++-common/Wunused-var-16.c | 4 | ||||
| -rw-r--r-- | gcc/tree-vect-generic.c | 7 |
2 files changed, 7 insertions, 4 deletions
diff --git a/gcc/testsuite/c-c++-common/Wunused-var-16.c b/gcc/testsuite/c-c++-common/Wunused-var-16.c index 8bdbcd3..31c7db3 100644 --- a/gcc/testsuite/c-c++-common/Wunused-var-16.c +++ b/gcc/testsuite/c-c++-common/Wunused-var-16.c @@ -1,6 +1,6 @@ /* PR c++/78949 */ /* { dg-do compile } */ -/* { dg-options "-Wunused" } */ +/* { dg-options "-Wunused -fdump-tree-optimized" } */ /* { dg-additional-options "-fno-common" { target hppa*-*-hpux* } } */ typedef unsigned char V __attribute__((vector_size(16))); @@ -14,3 +14,5 @@ foo () y &= ~x; v = y; } + +/* { dg-final { scan-tree-dump-not " ~0" "optimized" } } */ diff --git a/gcc/tree-vect-generic.c b/gcc/tree-vect-generic.c index 2e00b3e..0d7f041 100644 --- a/gcc/tree-vect-generic.c +++ b/gcc/tree-vect-generic.c @@ -2162,9 +2162,10 @@ expand_vector_operations_1 (gimple_stmt_iterator *gsi, if (op >= FIRST_NORM_OPTAB && op <= LAST_NORM_OPTAB && optab_handler (op, TYPE_MODE (TREE_TYPE (type))) != CODE_FOR_nothing) { - tree slhs = make_ssa_name (TREE_TYPE (TREE_TYPE (lhs))); - gimple *repl = gimple_build_assign (slhs, code, srhs1, srhs2); - gsi_insert_before (gsi, repl, GSI_SAME_STMT); + tree stype = TREE_TYPE (TREE_TYPE (lhs)); + tree slhs = (rhs2 != NULL_TREE) + ? gimplify_build2 (gsi, code, stype, srhs1, srhs2) + : gimplify_build1 (gsi, code, stype, srhs1); gimple_assign_set_rhs_from_tree (gsi, build_vector_from_val (type, slhs)); update_stmt (stmt); |