On Tue, Nov 25, 2014 at 4:01 PM, 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?
Oh, and note that I think DECL_ARG_TYPE is sth dangerous - it's meant to be a source language "ABI" kind-of-thing. Or rather an optimization hit. For example in C when integral promotions happen to call arguments this can be used to optimize sign-/zero-extensions in the callee. Unless something else overrides this (like the target which specifies the real ABI). IIRC. Richard. > 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; >> +}