On Thu, Jan 18, 2024 at 01:34:53PM +0100, Richard Biener wrote: > So - if we simply do > > /* If the input and output modes are both the same, we are done. */ > if (mode == GET_MODE (op0) || (mode == BLKmode && MEM_P (op0)) > ; > > ? After all if we want BLKmode we want a MEM, and if we have one > we should be done already. V_C_E isn't supposed to do any value > transform.
We'd need to make sure that op0 is actually MEM, which is not the case. The following patch seems to work though, the discover_nonconstant_array_refs_r part helps for -O2, the expr.cc part is needed at all optimization levels. 2024-01-18 Jakub Jelinek <ja...@redhat.com> * cfgexpand.cc (discover_nonconstant_array_refs_r): Force non-BLKmode VAR_DECLs referenced in BLKmode VIEW_CONVERT_EXPRs into memory. * expr.cc (expand_expr_real_1) <case VIEW_CONVERT_EXPR>: If mode is BLKmode and type a BITINT_TYPE from a non-BLKmode VAR_P with MEM DECL_RTL, use adjust_address to BLKmode for it instead of expand_expr. --- gcc/cfgexpand.cc.jj 2024-01-16 11:45:16.159326506 +0100 +++ gcc/cfgexpand.cc 2024-01-18 13:41:54.579551282 +0100 @@ -6380,11 +6380,16 @@ discover_nonconstant_array_refs_r (tree /* References of size POLY_INT_CST to a fixed-size object must go through memory. It's more efficient to force that here than to create temporary slots on the fly. - RTL expansion expectes TARGET_MEM_REF to always address actual memory. */ + RTL expansion expectes TARGET_MEM_REF to always address actual memory. + Also, force to stack non-BLKmode vars accessed through VIEW_CONVERT_EXPR + to BLKmode BITINT_TYPEs. */ else if (TREE_CODE (t) == TARGET_MEM_REF || (TREE_CODE (t) == MEM_REF && TYPE_SIZE (TREE_TYPE (t)) - && POLY_INT_CST_P (TYPE_SIZE (TREE_TYPE (t))))) + && POLY_INT_CST_P (TYPE_SIZE (TREE_TYPE (t)))) + || (TREE_CODE (t) == VIEW_CONVERT_EXPR + && TREE_CODE (TREE_TYPE (t)) == BITINT_TYPE + && TYPE_MODE (TREE_TYPE (t)) == BLKmode)) { tree base = get_base_address (t); if (base --- gcc/expr.cc.jj 2024-01-12 10:07:58.194851657 +0100 +++ gcc/expr.cc 2024-01-18 13:38:19.677556646 +0100 @@ -12382,6 +12382,17 @@ expand_expr_real_1 (tree exp, rtx target } } + /* Ensure non-BLKmode array VAR_DECLs VCEd to BLKmode BITINT_TYPE + aren't promoted to registers. */ + if (op0 == NULL_RTX + && mode == BLKmode + && TREE_CODE (type) == BITINT_TYPE + && VAR_P (treeop0) + && DECL_MODE (treeop0) != BLKmode + && DECL_RTL_SET_P (treeop0) + && MEM_P (DECL_RTL (treeop0))) + op0 = adjust_address (DECL_RTL (treeop0), BLKmode, 0); + if (!op0) op0 = expand_expr_real (treeop0, NULL_RTX, VOIDmode, modifier, NULL, inner_reference_p); Jakub