In the testcase we were trying to group two gather loads, even though that isn't supported. Fixed by explicitly disallowing grouping of gathers and scatters.
This problem didn't show up on SVE because there we convert to IFN_GATHER_LOAD/IFN_SCATTER_STORE pattern statements, which fail the can_group_stmts_p check. Tested on x86_64-linux-gnu. OK to install? Richard 2018-01-15 Richard Sandiford <richard.sandif...@linaro.org> gcc/ * tree-vect-data-refs.c (vect_analyze_data_ref_accesses): gcc/testsuite/ * gcc.dg/torture/pr83847.c: New test. Index: gcc/tree-vect-data-refs.c =================================================================== --- gcc/tree-vect-data-refs.c 2018-01-13 18:02:00.948360274 +0000 +++ gcc/tree-vect-data-refs.c 2018-01-15 12:22:47.066621712 +0000 @@ -2923,7 +2923,8 @@ vect_analyze_data_ref_accesses (vec_info data_reference_p dra = datarefs_copy[i]; stmt_vec_info stmtinfo_a = vinfo_for_stmt (DR_STMT (dra)); stmt_vec_info lastinfo = NULL; - if (! STMT_VINFO_VECTORIZABLE (stmtinfo_a)) + if (!STMT_VINFO_VECTORIZABLE (stmtinfo_a) + || STMT_VINFO_GATHER_SCATTER_P (stmtinfo_a)) { ++i; continue; @@ -2932,7 +2933,8 @@ vect_analyze_data_ref_accesses (vec_info { data_reference_p drb = datarefs_copy[i]; stmt_vec_info stmtinfo_b = vinfo_for_stmt (DR_STMT (drb)); - if (! STMT_VINFO_VECTORIZABLE (stmtinfo_b)) + if (!STMT_VINFO_VECTORIZABLE (stmtinfo_b) + || STMT_VINFO_GATHER_SCATTER_P (stmtinfo_b)) break; /* ??? Imperfect sorting (non-compatible types, non-modulo Index: gcc/testsuite/gcc.dg/torture/pr83847.c =================================================================== --- /dev/null 2018-01-12 06:40:27.684409621 +0000 +++ gcc/testsuite/gcc.dg/torture/pr83847.c 2018-01-15 12:22:47.064621805 +0000 @@ -0,0 +1,32 @@ +/* { dg-do compile } */ +/* { dg-additional-options "-march=bdver4" { target i?86-*-* x86_64-*-* } } */ + +typedef struct { + struct { + int a; + int b; + } c; +} * d; +typedef struct { + unsigned e; + d f[]; +} g; +g h; +d *k; +int i(int j) { + if (j) { + *k = *h.f; + return 1; + } + return 0; +} +int l; +int m; +int n; +d o; +void p() { + for (; i(l); l++) { + n += o->c.a; + m += o->c.b; + } +}