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Date: Tue, 19 Apr 2022 16:06:44 -0500
From: Segher Boessenkool <segher@kernel.crashing.org>
To: HAO CHEN GUI <guihaoc@linux.ibm.com>
Cc: Alexandre Oliva <oliva@adacore.com>,
 HAO CHEN GUI via Gcc-patches <gcc-patches@gcc.gnu.org>,
 Bill Schmidt <wschmidt@linux.ibm.com>, David <dje.gcc@gmail.com>
Subject: Re: Ping^2 [PATCH, rs6000] Correct match pattern in pr56605.c
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On Tue, Apr 19, 2022 at 04:05:06PM +0800, HAO CHEN GUI wrote:
>    I tested the test case on Linux and AIX with both big and little endian.
> The test case requires lp64 target, so it won't be tested on 32-bit targets.
> 
> On big endian (both AIX and Linux), it should match
> (compare:CC (and:SI (subreg:SI (reg:DI 207) 4)
> 
> On little endian (both AIX and Linux), it should match
> (compare:CC (and:SI (subreg:SI (reg:DI 207) 0)
> 
> So, the pattern in my patch should work fine.
> 
> /* { dg-final { scan-rtl-dump-times {\(compare:CC \(and:SI \(subreg:SI \(reg:DI} 1 "combine" } } */

On powerpc64-linux:

FAIL: gcc.target/powerpc/pr56605.c scan-rtl-dump-times combine "\\(compare:CC \\((?:and|zero_extend):(?:[SD]I) \\((?:sub)?reg:[SD]I" 1

It matches twice instead of once, namely:

(insn 19 18 20 2 (parallel [
            (set (reg:CC 208)
                (compare:CC (and:SI (subreg:SI (reg:DI 207) 4)
                        (const_int 3 [0x3]))
                    (const_int 0 [0])))
            (set (reg:SI 129 [ prolog_loop_niters.5 ])
                (and:SI (subreg:SI (reg:DI 207) 4)
                    (const_int 3 [0x3])))
        ]) 208 {*andsi3_imm_mask_dot2}
     (nil))

(insn 81 80 82 11 (parallel [
            (set (reg:CC 232)
                (compare:CC (and:DI (subreg:DI (reg:SI 136 [ niters.6 ]) 0)
                        (const_int 7 [0x7]))
                    (const_int 0 [0])))
            (clobber (scratch:DI))
        ]) 207 {*anddi3_imm_mask_dot}
     (expr_list:REG_DEAD (reg:SI 136 [ niters.6 ])
        (nil)))

The paradoxical subreg in the latter wasn't expected :-)


Segher