expand_call_mem_ref checks for TARGET_MEM_REFs that have compatible type, but it didn't then go on to install the specific type we need, which might have different alignment due to:
if (TYPE_ALIGN (type) != align) type = build_aligned_type (type, align); This was causing masked stores to be incorrectly marked as aligned on AVX512. Tested on aarch64-linux-gnu, x86_64-linux-gnu and powerpc64-linux-gnu. Also tested by Alexander on AVX512 hw. OK to install? Richard 2018-02-20 Richard Sandiford <richard.sandif...@linaro.org> gcc/ PR tree-optimization/84419 * internal-fn.c (expand_call_mem_ref): Create a TARGET_MEM_REF with the required type if its current type is compatible but different. gcc/testsuite/ PR tree-optimization/84419 * gcc.dg/vect/pr84419.c: New test. Index: gcc/internal-fn.c =================================================================== --- gcc/internal-fn.c 2018-01-13 18:01:51.235735290 +0000 +++ gcc/internal-fn.c 2018-02-20 09:40:47.547217244 +0000 @@ -2444,11 +2444,14 @@ expand_call_mem_ref (tree type, gcall *s && types_compatible_p (TREE_TYPE (mem), type)) { tree offset = TMR_OFFSET (mem); - if (alias_ptr_type != TREE_TYPE (offset) || !integer_zerop (offset)) + if (type != TREE_TYPE (mem) + || alias_ptr_type != TREE_TYPE (offset) + || !integer_zerop (offset)) { mem = copy_node (mem); TMR_OFFSET (mem) = wide_int_to_tree (alias_ptr_type, wi::to_poly_wide (offset)); + TREE_TYPE (mem) = type; } return mem; } Index: gcc/testsuite/gcc.dg/vect/pr84419.c =================================================================== --- /dev/null 2018-02-19 19:34:42.906488063 +0000 +++ gcc/testsuite/gcc.dg/vect/pr84419.c 2018-02-20 09:40:47.548217201 +0000 @@ -0,0 +1,21 @@ +#include <string.h> + +#define SIZE 400 + +int foo[SIZE]; +char bar[SIZE]; + +void __attribute__ ((noinline)) foo_func(void) +{ + int i; + for (i = 1; i < SIZE; i++) + if (bar[i]) + foo[i] = 1; +} + +int main() +{ + memset(bar, 1, sizeof(bar)); + foo_func(); + return 0; +}