I have a simple reduction test. (attachment to follow)
I'm compiling it with:
../ppc_build/gcc/cc1 -mcpu=G4 -maltivec -O3 -ftree-vectorize reductest.c
If the types are all unsigned, the loop is vectorized.
If the types are all signed, the vectorizer bails because it doesn't know some
pattern and there are suspicious unsigned types in the log:
reductest.c:8: note: Detected induction.
reductest.c:8: note: === vect_mark_stmts_to_be_vectorized ===
reductest.c:8: note: init: phi relevant? ivtmp.30_19 = PHI <ivtmp.30_18(2),
512(0)>;
reductest.c:8: note: init: phi relevant? sum_22 = PHI <sum_13(2), 0(0)>;
reductest.c:8: note: init: phi relevant? i_21 = PHI <i_15(2), 0(0)>;
reductest.c:8: note: init: phi relevant? a_20 = PHI <a_14(2), a_6(0)>;
reductest.c:8: note: init: stmt relevant? <L0>:
reductest.c:8: note: init: stmt relevant? D.1686_9 = *a_20
reductest.c:8: note: init: stmt relevant? D.1687_10 = (short unsigned int)
D.1686_9
reductest.c:8: note: init: stmt relevant? sum.0_11 = (short unsigned int)
sum_22
reductest.c:8: note: init: stmt relevant? D.1689_12 = D.1687_10 + sum.0_11
reductest.c:8: note: init: stmt relevant? sum_13 = (short int) D.1689_12
reductest.c:8: note: vec_stmt_relevant_p: used out of loop.
reductest.c:8: note: mark relevant 0, live 1.
reductest.c:8: note: init: stmt relevant? a_14 = a_20 + 2B
reductest.c:8: note: init: stmt relevant? i_15 = i_21 + 1
reductest.c:8: note: init: stmt relevant? ivtmp.30_18 = ivtmp.30_19 - 1
reductest.c:8: note: init: stmt relevant? if (ivtmp.30_18 != 0) goto <L6>; else
goto <L2>;
reductest.c:8: note: init: stmt relevant? <L6>:
reductest.c:8: note: worklist: examine stmt: sum_13 = (short int) D.1689_12
reductest.c:8: note: vect_is_simple_use: operand D.1689_12
reductest.c:8: note: def_stmt: D.1689_12 = D.1687_10 + sum.0_11
reductest.c:8: note: type of def: 2.
reductest.c:8: note: worklist: examine use 2: D.1689_12
reductest.c:8: note: mark relevant 0, live 1.
reductest.c:8: note: worklist: examine stmt: D.1689_12 = D.1687_10 + sum.0_11
reductest.c:8: note: vect_is_simple_use: operand D.1687_10
reductest.c:8: note: def_stmt: D.1687_10 = (short unsigned int) D.1686_9
reductest.c:8: note: type of def: 2.
reductest.c:8: note: worklist: examine use 2: D.1687_10
reductest.c:8: note: mark relevant 0, live 1.
reductest.c:8: note: vect_is_simple_use: operand sum.0_11
reductest.c:8: note: def_stmt: sum.0_11 = (short unsigned int) sum_22
reductest.c:8: note: type of def: 2.
reductest.c:8: note: worklist: examine use 2: sum.0_11
reductest.c:8: note: mark relevant 0, live 1.
reductest.c:8: note: worklist: examine stmt: sum.0_11 = (short unsigned int)
sum_22
reductest.c:8: note: vect_is_simple_use: operand sum_22
reductest.c:8: note: def_stmt: sum_22 = PHI <sum_13(2), 0(0)>;
reductest.c:8: note: Unsupported pattern.
reductest.c:8: note: not vectorized: unsupported use in stmt.
reductest.c:8: note: unexpected pattern.
reductest.c:8: note: vectorized 0 loops in function.
I have not yet checked out the 4.1 tip or mainline to try this there...
--
Summary: autovectorizer converts signed types to unsigned, then
can't match patterns
Product: gcc
Version: 4.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: eplondke at gmail dot com
GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: powerpc-linux and others
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29170
