[PATCH] D153607: [CSKY] Optimize conditional branch with BHZ32/BHSZ32/BLSZ32/BLZ32

[Sergei Barannikov via Phabricator via llvm-commits]

barannikov88 added a comment.

In D153607#4467588 <https://reviews.llvm.org/D153607#4467588>, @benshi001 wrote:

> In D153607#4467587 <https://reviews.llvm.org/D153607#4467587>, @barannikov88 wrote:
>
>> In D153607#4462927 <https://reviews.llvm.org/D153607#4462927>, @benshi001 wrote:
>>
>>> In D153607#4462762 <https://reviews.llvm.org/D153607#4462762>, @zixuan-wu wrote:
>>>
>>>> need more case about bhz/bhsz?
>>>
>>> It is hard to add tests for
>>>
>>>   def : Pat<(brcond (i32 (setge GPR:$rs1, (i32 1))), bb:$imm16),
>>>             (BHZ32 GPR:$rs1, bb:$imm16)>;
>>>
>>> Since the original IR pattern
>>>
>>>   %icmp = icmp sge i32 %x, 1
>>>   br i1 %icmp, label %label1, label %label2
>>>
>>> is always transformed to an equivalent form by DAGCombiner
>>>
>>>   %icmp = icmp slt i32 %x, 1
>>>   br i1 %icmp, label %label2, label %label1
>>>
>>> before reaching to the CSKY backend.
>>>
>>> And `BHSZ32` has the same issue.
>>>
>>> I add these two `Pat`s for `BHSZ32` and `BHZ32`, just in case there is future changes in the DAGCombiner.
>>
>> Try something like:
>>
>>   extern void on_false(void);
>>   void test_ge_1(int x) {
>>     if (!(x >= 1))
>>       on_false();
>>   }
>
> Unfortunately your program can not lead to `BHSZ` or `BHZ`, still `BLSZ` as follow,
>
>           .type   test_ge_1, at function
>   test_ge_1:                              # @test_ge_1
>   # %bb.0:
>           subi16  sp, sp, 4
>           st32.w  lr, (sp, 0)                     # 4-byte Folded Spill
>           blsz32  a0, .LBB0_2
>   # %bb.1:
>           ld32.w  lr, (sp, 0)                     # 4-byte Folded Reload
>           addi16  sp, sp, 4
>           rts16
>   .LBB0_2:
>           jsri32  [.LCPI0_0]
>           ld32.w  lr, (sp, 0)                     # 4-byte Folded Reload
>           addi16  sp, sp, 4
>           rts16
>           .p2align        1
>   # %bb.3:
>           .p2align        2, 0x0
>   .LCPI0_0:
>           .long   on_false
>   .Lfunc_end0:
>           .size   test_ge_1, .Lfunc_end0-test_ge_1
>                                           # -- End function

It does test the pattern though. You can see BHZ32 if you pass -stop-after=finalize-isel.


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