llvm dev - Apr 2019 - How to use the pass 'Unroll and Jam'

Dear LLVM developers,

Recently I want to try the pass '-loop-unroll-and-jam' to observe how
the
IR is transformed, but I don't see the IR changed after doing the following
steps.

Here are the details for preparing my experiment and I have tried the LLVM
6, 7 and 8:

1) Simple 2D array source code (loop.c) is given

```
#define M 32768
#define N 32768

double a[M][N], b[M][N], c[M][N];

int main() {
    for (int i = 0; i < M; i++) {
        for (int j = 0; j < N; j++) {
            c[i][j] = a[i][j] + b[i][j];
        }
    }
    return 0;
}
```

2) Create an LLVM IR file
./bin/clang -O1 loop.c -emit-llvm -S -o loop.ll

3) Run the 'unroll-and-jam' pass
./bin/opt -loop-unroll-and-jam loop.ll -S -o loop-unrolljam.ll

I added the option '--debug-pass=Structure' to the opt, and I can see
the
'Unroll and Jam loops' indeed executed by the Loop Pass Manager.
```
   ModulePass Manager
       FunctionPass Manager
        Dominator Tree Construction
        Basic Alias Analysis (stateless AA impl)
        Function Alias Analysis Results
        Natural Loop Information
        Scalar Evolution Analysis
        Dependence Analysis
        Canonicalize natural loops
        LCSSA Verifier
        Loop-Closed SSA Form Pass
        Loop Pass Manager
          Unroll and Jam loops
        Module Verifier
       Print Module IR
```

I also tried to add the option '-debug' to the opt to see if there is
the
debug information printed by LoopUnrollAndJam, but nothing.

Thank you very much.
-- 
Zhen Wei (魏禛)
Master Student
Department of Computer Science & Information  Engineering
National Taiwan University
Email:  zhenwei.tw at gmail.com
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Try the combo:

-enable-unroll-and-jam -allow-unroll-and-jam -unroll-and-jam-count=4

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of ZHEN WEI
via llvm-dev
Sent: Thursday, April 25, 2019 12:13 PM
To: llvm-dev at lists.llvm.org
Subject: [llvm-dev] How to use the pass 'Unroll and Jam'

Dear LLVM developers,

Recently I want to try the pass '-loop-unroll-and-jam' to observe how
the IR is transformed, but I don't see the IR changed after doing the
following steps.

Here are the details for preparing my experiment and I have tried the LLVM 6, 7
and 8:
1) Simple 2D array source code (loop.c) is given

```
#define M 32768
#define N 32768

double a[M][N], b[M][N], c[M][N];

int main() {
    for (int i = 0; i < M; i++) {
        for (int j = 0; j < N; j++) {
            c[i][j] = a[i][j] + b[i][j];
        }
    }
    return 0;
}
```
2) Create an LLVM IR file
./bin/clang -O1 loop.c -emit-llvm -S -o loop.ll

3) Run the 'unroll-and-jam' pass
./bin/opt -loop-unroll-and-jam loop.ll -S -o loop-unrolljam.ll

I added the option '--debug-pass=Structure' to the opt, and I can see
the 'Unroll and Jam loops' indeed executed by the Loop Pass Manager.
```
   ModulePass Manager
       FunctionPass Manager
        Dominator Tree Construction
        Basic Alias Analysis (stateless AA impl)
        Function Alias Analysis Results
        Natural Loop Information
        Scalar Evolution Analysis
        Dependence Analysis
        Canonicalize natural loops
        LCSSA Verifier
        Loop-Closed SSA Form Pass
        Loop Pass Manager
          Unroll and Jam loops
        Module Verifier
       Print Module IR
```

I also tried to add the option '-debug' to the opt to see if there is
the debug information printed by LoopUnrollAndJam, but nothing.

Thank you very much.
--
Zhen Wei (魏禛)
Master Student
Department of Computer Science & Information  Engineering
National Taiwan University
Email:  zhenwei.tw at gmail.com<mailto:zhenwei.tw at gmail.com>
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Hi Das,

Thanks for your reply! I have received similar responses from @LebedevRI on
the IRC.

After I modified the arguments for opt as the following, my loops can be
unroll-and-jam successfully:
-loop-unroll-and-jam -allow-unroll-and-jam -unroll-and-jam-count=2

'loop-unroll-and-jam' and 'allow-unroll-and-jam' are both needed
to turn on
the functionality.

Thanks again. Have a nice day.

Das, Dibyendu <Dibyendu.Das at amd.com> 於 2019年4月25日 週四 下午4:24寫道：
> Try the combo:
>
>
>
> -enable-unroll-and-jam -allow-unroll-and-jam -unroll-and-jam-count=4
>
>
>
> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> *On Behalf Of
*ZHEN
> WEI via llvm-dev
> *Sent:* Thursday, April 25, 2019 12:13 PM
> *To:* llvm-dev at lists.llvm.org
> *Subject:* [llvm-dev] How to use the pass 'Unroll and Jam'
>
>
>
> Dear LLVM developers,
>
>
>
> Recently I want to try the pass '-loop-unroll-and-jam' to observe
how the
> IR is transformed, but I don't see the IR changed after doing the
following
> steps.
>
>
>
> Here are the details for preparing my experiment and I have tried the LLVM
> 6, 7 and 8:
>
> 1) Simple 2D array source code (loop.c) is given
>
>
>
> ```
>
> #define M 32768
>
> #define N 32768
>
>
>
> double a[M][N], b[M][N], c[M][N];
>
>
>
> int main() {
>
>     for (int i = 0; i < M; i++) {
>
>         for (int j = 0; j < N; j++) {
>
>             c[i][j] = a[i][j] + b[i][j];
>
>         }
>
>     }
>
>     return 0;
>
> }
>
> ```
>
> 2) Create an LLVM IR file
>
> ./bin/clang -O1 loop.c -emit-llvm -S -o loop.ll
>
>
>
> 3) Run the 'unroll-and-jam' pass
>
> ./bin/opt -loop-unroll-and-jam loop.ll -S -o loop-unrolljam.ll
>
>
>
> I added the option '--debug-pass=Structure' to the opt, and I can
see the
> 'Unroll and Jam loops' indeed executed by the Loop Pass Manager.
>
> ```
>
>    ModulePass Manager
>        FunctionPass Manager
>         Dominator Tree Construction
>         Basic Alias Analysis (stateless AA impl)
>         Function Alias Analysis Results
>         Natural Loop Information
>         Scalar Evolution Analysis
>         Dependence Analysis
>         Canonicalize natural loops
>         LCSSA Verifier
>         Loop-Closed SSA Form Pass
>         Loop Pass Manager
>           Unroll and Jam loops
>         Module Verifier
>        Print Module IR
>
> ```
>
>
>
> I also tried to add the option '-debug' to the opt to see if there
is the
> debug information printed by LoopUnrollAndJam, but nothing.
>
>
>
> Thank you very much.
>
> --
>
> Zhen Wei (魏禛)
> Master Student
> Department of Computer Science & Information  Engineering
> National Taiwan University
> Email:  zhenwei.tw at gmail.com
>

-- 
Zhen Wei (魏禛)
Master Student
Department of Computer Science & Information  Engineering
National Taiwan University
Email:  zhenwei.tw at gmail.com
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