Hello! > On Tue, Nov 25, 2014 at 5:05 PM, H.J. Lu <hjl.to...@gmail.com> wrote: >> On Tue, Nov 25, 2014 at 7:01 AM, Richard Biener >> <richard.guent...@gmail.com> wrote: >>> On Tue, Nov 25, 2014 at 1:57 PM, H.J. Lu <hongjiu...@intel.com> wrote: >>>> Hi, >>>> >>>> The enclosed testcase fails on x86 when compiled with -Os since we pass >>>> a byte parameter with a byte load in caller and read it as an int in >>>> callee. The reason it only shows up with -Os is x86 backend encodes >>>> a byte load with an int load if -O isn't used. When a byte load is >>>> used, the upper 24 bits of the register have random value for none >>>> WORD_REGISTER_OPERATIONS targets. >>>> >>>> It happens because setup_incoming_promotions in combine.c has >>>> >>>> /* The mode and signedness of the argument before any promotions >>>> happen >>>> (equal to the mode of the pseudo holding it at that stage). */ >>>> mode1 = TYPE_MODE (TREE_TYPE (arg)); >>>> uns1 = TYPE_UNSIGNED (TREE_TYPE (arg)); >>>> >>>> /* The mode and signedness of the argument after any source language >>>> and >>>> TARGET_PROMOTE_PROTOTYPES-driven promotions. */ >>>> mode2 = TYPE_MODE (DECL_ARG_TYPE (arg)); >>>> uns3 = TYPE_UNSIGNED (DECL_ARG_TYPE (arg)); >>>> >>>> /* The mode and signedness of the argument as it is actually passed, >>>> after any TARGET_PROMOTE_FUNCTION_ARGS-driven ABI promotions. */ >>>> mode3 = promote_function_mode (DECL_ARG_TYPE (arg), mode2, &uns3, >>>> TREE_TYPE (cfun->decl), 0); >>>> >>>> while they are actually passed in register by assign_parm_setup_reg in >>>> function.c: >>>> >>>> /* Store the parm in a pseudoregister during the function, but we may >>>> need to do it in a wider mode. Using 2 here makes the result >>>> consistent with promote_decl_mode and thus expand_expr_real_1. */ >>>> promoted_nominal_mode >>>> = promote_function_mode (data->nominal_type, data->nominal_mode, >>>> &unsignedp, >>>> TREE_TYPE (current_function_decl), 2); >>>> >>>> where nominal_type and nominal_mode are set up with TREE_TYPE (parm) >>>> and TYPE_MODE (nominal_type). TREE_TYPE here is >>> >>> I think the bug is here, not in combine.c. Can you try going back in >>> history >>> for both snippets and see if they matched at some point? >>> >> >> The bug was introduced by >> >> https://gcc.gnu.org/ml/gcc-cvs/2007-09/msg00613.html >> >> commit 5d93234932c3d8617ce92b77b7013ef6bede9508 >> Author: shinwell <shinwell@138bc75d-0d04-0410-961f-82ee72b054a4> >> Date: Thu Sep 20 11:01:18 2007 +0000 >> >> gcc/ >> * combine.c: Include cgraph.h. >> (setup_incoming_promotions): Rework to allow more aggressive >> elimination of sign extensions when all call sites of the >> current function are known to lie within the current unit. >> >> >> git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@128618 >> 138bc75d-0d04-0410-961f-82ee72b054a4 >> >> Before this commit, combine.c has >> >> enum machine_mode mode = TYPE_MODE (TREE_TYPE (arg)); >> int uns = TYPE_UNSIGNED (TREE_TYPE (arg)); >> >> mode = promote_mode (TREE_TYPE (arg), mode, &uns, 1); >> if (mode == GET_MODE (reg) && mode != DECL_MODE (arg)) >> { >> rtx x; >> x = gen_rtx_CLOBBER (DECL_MODE (arg), const0_rtx); >> x = gen_rtx_fmt_e ((uns ? ZERO_EXTEND : SIGN_EXTEND), mode, x); >> record_value_for_reg (reg, first, x); >> } >> >> It matches function.c: >> >> /* This is not really promoting for a call. However we need to be >> consistent with assign_parm_find_data_types and expand_expr_real_1. */ >> promoted_nominal_mode >> = promote_mode (data->nominal_type, data->nominal_mode, &unsignedp, 1); >> >> r128618 changed >> >> mode = promote_mode (TREE_TYPE (arg), mode, &uns, 1); >> >> to >> >> mode3 = promote_mode (DECL_ARG_TYPE (arg), mode2, &uns3, 1); >> >> It breaks none WORD_REGISTER_OPERATIONS targets. > > Hmm, I think that DECL_ARG_TYPE makes a difference only > for non-WORD_REGISTER_OPERATIONS targets. > > But yeah, isolated the above change looks wrong. > > Your patch is ok for trunk if nobody objects within 24h and for branches > after a week. > > Thanks, > Richard.
This patch caused PR64213. Uros.
