The IFN_GOMP_SIMD_LANE handling in vectorizable_store tries to use MEM_REF
offsets to maintain pointer disambiguation info.  This patch makes sure
that we don't try to do the same optimisation for IFN_MASK_STOREs, which
have no similar offset argument.

The patch fixes libgomp.c-c++-common/pr66199-*.c for SVE.  Previously
we had an ncopies==2 store and stored both halves to the same address.

Tested on aarch64-linux-gnu (with and without SVE), aarch64_be-elf
and x86_64-linux-gnu.  OK to install?

Richard


2019-01-07  Richard Sandiford  <richard.sandif...@arm.com>

gcc/
        * tree-vect-stmts.c (vectorizable_store): Don't use the dataref_offset
        optimization for masked stores.

Index: gcc/tree-vect-stmts.c
===================================================================
--- gcc/tree-vect-stmts.c       2019-01-04 11:39:27.190246648 +0000
+++ gcc/tree-vect-stmts.c       2019-01-07 13:23:28.048406652 +0000
@@ -7059,6 +7059,7 @@ vectorizable_store (stmt_vec_info stmt_i
          bool simd_lane_access_p
            = STMT_VINFO_SIMD_LANE_ACCESS_P (stmt_info);
          if (simd_lane_access_p
+             && !loop_masks
              && TREE_CODE (DR_BASE_ADDRESS (first_dr_info->dr)) == ADDR_EXPR
              && VAR_P (TREE_OPERAND (DR_BASE_ADDRESS (first_dr_info->dr), 0))
              && integer_zerop (DR_OFFSET (first_dr_info->dr))

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