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? Thanks, Richard. > (gdb) call debug_tree (type) > <enumeral_type 0x7ffff19f85e8 X > type <integer_type 0x7ffff18a93f0 unsigned char public unsigned > string-flag QI > size <integer_cst 0x7ffff18a5fa8 constant 8> > unit size <integer_cst 0x7ffff18a5fc0 constant 1> > align 8 symtab 0 alias set -1 canonical type 0x7ffff18a93f0 > precision 8 min <integer_cst 0x7ffff18a5fd8 0> max <integer_cst > 0x7ffff18a5f78 255>> > static unsigned type_5 QI size <integer_cst 0x7ffff18a5fa8 8> unit > size <integer_cst 0x7ffff18a5fc0 1> > align 8 symtab 0 alias set -1 canonical type 0x7ffff19f85e8 > precision 8 min <integer_cst 0x7ffff18a5fd8 0> max <integer_cst > 0x7ffff18a5f78 255> > values <tree_list 0x7ffff19fb028 > purpose <identifier_node 0x7ffff19f6738 V > bindings <(nil)> > local bindings <(nil)>> > value <const_decl 0x7ffff18c21c0 V type <enumeral_type > 0x7ffff19f85e8 X> > readonly constant used VOID file pr64037.ii line 2 col 3 > align 1 context <enumeral_type 0x7ffff19f85e8 X> initial > <integer_cst 0x7ffff19d8d08 2>>> context <translation_unit_decl > 0x7ffff7ff91e0 D.1> > chain <type_decl 0x7ffff19f5c78 X>> > (gdb) > > and DECL_ARG_TYPE is > > (gdb) call debug_tree (type) > <integer_type 0x7ffff18a9690 int public SI > size <integer_cst 0x7ffff18a5e70 type <integer_type 0x7ffff18a9150 > bitsizetype> constant 32> > unit size <integer_cst 0x7ffff18a5e88 type <integer_type > 0x7ffff18a90a8 sizetype> constant 4> > align 32 symtab 0 alias set 1 canonical type 0x7ffff18a9690 > precision 32 min <integer_cst 0x7ffff18c60c0 -2147483648> max > <integer_cst 0x7ffff18c60d8 2147483647> > pointer_to_this <pointer_type 0x7ffff18cb930>> > (gdb) > > This mismatch makes combine thinks a byte parameter is passed as int > in register and turns > > (insn 9 6 10 2 (set (reg:SI 92 [ b ]) > (zero_extend:SI (subreg:QI (reg:SI 91 [ b ]) 0))) pr64037.ii:9 > 138 {*zero_extendqisi2} > (expr_list:REG_DEAD (reg:SI 91 [ b ]) > (nil))) > (insn 10 9 0 2 (set (mem:SI (reg/v/f:SI 88 [ out ]) [1 *out_4(D)+0 S4 > A32]) > (reg:SI 92 [ b ])) pr64037.ii:9 90 {*movsi_internal} > (expr_list:REG_DEAD (reg:SI 92 [ b ]) > (expr_list:REG_DEAD (reg/v/f:SI 88 [ out ]) > (nil)))) > > into > > Trying 9 -> 10: > Successfully matched this instruction: > (set (mem:SI (reg/v/f:SI 88 [ out ]) [1 *out_4(D)+0 S4 A32]) > (reg:SI 91 [ b ])) > allowing combination of insns 9 and 10 > original costs 6 + 4 = 10 > replacement cost 4 > deferring deletion of insn with uid = 9. > modifying insn i3 10: [r88:SI]=r91:SI > REG_DEAD r91:SI > REG_DEAD r88:SI > > > This patch makes setup_incoming_promotions to match assign_parm_setup_reg. > Tested on Linux/x86-64 without regressions. OK for trunk and backport? > > Thanks. > > > H.J. > ---- > diff --git a/gcc/combine.c b/gcc/combine.c > index 1808f97..a0449a2 100644 > --- a/gcc/combine.c > +++ b/gcc/combine.c > @@ -1561,8 +1561,8 @@ setup_incoming_promotions (rtx_insn *first) > 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, > + see assign_parm_setup_reg in function.c. */ > + mode3 = promote_function_mode (TREE_TYPE (arg), mode1, &uns1, > TREE_TYPE (cfun->decl), 0); > > /* The mode of the register in which the argument is being passed. */ > diff --git a/gcc/testsuite/g++.dg/pr64037.C b/gcc/testsuite/g++.dg/pr64037.C > new file mode 100644 > index 0000000..e5cd0e2 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/pr64037.C > @@ -0,0 +1,27 @@ > +// { dg-do run { target i?86-*-* x86_64-*-* } } > +// { dg-options "-std=c++11 -Os" } > + > +enum class X : unsigned char { > + V = 2, > +}; > + > +static void > +__attribute__((noinline,noclone)) > +foo(unsigned &out, unsigned a, X b) > +{ > + out = static_cast<unsigned>(b); > +} > + > +int main() > +{ > + unsigned deadbeef = 0xDEADBEEF; > + asm volatile ("" : "+d" (deadbeef), "+c" (deadbeef)); > + > + unsigned out; > + foo(out, 2, X::V); > + > + if (out != 2) > + __builtin_abort (); > + > + return 0; > +}