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Relax ix86_hardreg_mov_ok after split1.

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ix86_hardreg_mov_ok is added by r11-5066-gbe39636d9f68c4

>    The solution proposed here is to have the x86 backend/recog prevent
>    early RTL passes composing instructions (that set likely_spilled hard
>    registers) that they (combine) can't simplify, until after reload.
>    We allow sets from pseudo registers, immediate constants and memory
>    accesses, but anything more complicated is performed via a temporary
>    pseudo.  Not only does this simplify things for the register allocator,
>    but any remaining register-to-register moves are easily cleaned up
>    by the late optimization passes after reload, such as peephole2 and
>    cprop_hardreg.

The restriction is mainly for rtl optimization passes before pass_combine.

But split1 splits

```
(insn 17 13 18 2 (set (reg/i:V4SI 20 xmm0)
        (vec_merge:V4SI (const_vector:V4SI [
                    (const_int -1 [0xffffffffffffffff]) repeated x4
                ])
            (const_vector:V4SI [
                    (const_int 0 [0]) repeated x4
                ])
            (unspec:QI [
                    (reg:V4SF 106)
                    (reg:V4SF 102)
                    (const_int 0 [0])
                ] UNSPEC_PCMP))) "/app/example.cpp":20:1 2929 {*avx_cmpv4sf3_1}
     (expr_list:REG_DEAD (reg:V4SF 102)
        (expr_list:REG_DEAD (reg:V4SF 106)
            (nil))))
```

into:
```
(insn 23 13 24 2 (set (reg:V4SF 107)
        (unspec:V4SF [
                (reg:V4SF 106)
                (reg:V4SF 102)
                (const_int 0 [0])
            ] UNSPEC_PCMP)) "/app/example.cpp":20:1 -1
     (nil))
(insn 24 23 18 2 (set (reg/i:V4SI 20 xmm0)
        (subreg:V4SI (reg:V4SF 107) 0)) "/app/example.cpp":20:1 -1
     (nil))
```

There're many splitters generating MOV insn with SUBREG and would have
same problem.
Instead of changing those splitters one by one, the patch relaxes
ix86_hard_mov_ok to allow mov subreg to hard register after
split1. ix86_pre_reload_split () is used to replace
!reload_completed && ira_in_progress.

gcc/ChangeLog:

	* config/i386/i386.cc (ix86_hardreg_mov_ok): Relax mov subreg
	to hard register after split1.

gcc/testsuite/ChangeLog:

	* g++.target/i386/pr115982.C: New test.
This commit is contained in:
liuhongt 2024-07-22 11:36:59 +08:00
parent f4062e361c
commit a3f0389106
2 changed files with 13 additions and 3 deletions
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5
gcc/config/i386/i386.cc
View file

@ -20212,7 +20212,7 @@ ix86_class_likely_spilled_p (reg_class_t rclass)
}
/* Return true if a set of DST by the expression SRC should be allowed.
This prevents complex sets of likely_spilled hard regs before reload. */
This prevents complex sets of likely_spilled hard regs before split1. */
bool
ix86_hardreg_mov_ok (rtx dst, rtx src)
@ -20224,8 +20224,7 @@ ix86_hardreg_mov_ok (rtx dst, rtx src)
? standard_sse_constant_p (src, GET_MODE (dst))
: x86_64_immediate_operand (src, GET_MODE (dst)))
&& ix86_class_likely_spilled_p (REGNO_REG_CLASS (REGNO (dst)))
&& !reload_completed
&& !lra_in_progress)
&& ix86_pre_reload_split ())
return false;
return true;
}

11
gcc/testsuite/g++.target/i386/pr115982.C Normal file
View file

@ -0,0 +1,11 @@
/* { dg-do compile } */
/* { dg-options "-mavx512vl -O2" } */
typedef float VF __attribute__((__vector_size__(16)));
typedef int VI __attribute__((__vector_size__(16)));
VI
foo (VF x)
{
return !x;
}