Hi all, In this wrong-code issue the RTL tries to load a const_vector: (const_vector:V8QI [ (const_int 1 [0x1]) (const_int 0 [0]) (const_int 1 [0x1]) (const_int 0 [0]) (const_int 1 [0x1]) (const_int 0 [0]) (const_int 1 [0x1]) (const_int 0 [0]) ])
into a NEON register. The logic for that is in neon_valid_immediate which does a number of tricks to decide what value and of what size to do a VMOV on to load the correct vector immediate into the register. It goes wrong on big-endian. On both big and little-endian this outputs: vmov.i16 d18, #0x1 This is wrong on big-endian. The vector layout has to be such as if loaded from memory. I've tried various approaches of fixing neon_valid_immediate to generate the correct immediate but have been unsuccessful, resulting in regressions in various parts of the testsuite or making a big mess of the function. Given that armeb is not a target of major concern I believe the safest route at this stage is to only allow vector constants that will obviously work on big-endian, that is the ones that are just a single element duplicated in all lanes. This patch fixes the execution failures: FAIL: gfortran.dg/intrinsic_pack_1.f90 FAIL: gfortran.dg/c_f_pointer_logical.f03 FAIL: gcc.dg/torture/pr60183.c FAIL: gcc.dg/vect/pr51581-4.c on armeb-none-eabi. Ok for trunk? Thanks, Kyrill 2017-01-06 Kyrylo Tkachov <kyrylo.tkac...@arm.com> PR target/71270 * config/arm/arm.c (neon_valid_immediate): Reject vector constants in big-endian mode when they are not a single duplicated value.
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c index 45e0a3cd11fa650f456f7382ffbbcd1c932b95eb..2beee8ebe94eeadd6fb1d5b119e3b474e1ab902a 100644 --- a/gcc/config/arm/arm.c +++ b/gcc/config/arm/arm.c @@ -11542,6 +11542,12 @@ neon_valid_immediate (rtx op, machine_mode mode, int inverse, return 18; } + /* The tricks done in the code below apply for little-endian vector layout. + For big-endian vectors only allow vectors of the form { a, a, a..., a }. + FIXME: Implement logic for big-endian vectors. */ + if (BYTES_BIG_ENDIAN && vector && !const_vec_duplicate_p (op)) + return -1; + /* Splat vector constant out into a byte vector. */ for (i = 0; i < n_elts; i++) {