[polly] r238929 - Lower signed-divisions without rounding to ashr instructions

[Johannes Doerfert]

Isnt't there a LLVM pass that will do this kind of optimization
(Instcombine)?


On 06/03, Tobias Grosser wrote:
> Author: grosser
> Date: Wed Jun  3 10:14:58 2015
> New Revision: 238929
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=238929&view=rev
> Log:
> Lower signed-divisions without rounding to ashr instructions
> 
> Modified:
>     polly/trunk/lib/CodeGen/IslExprBuilder.cpp
>     polly/trunk/test/Isl/CodeGen/exprModDiv.ll
> 
> Modified: polly/trunk/lib/CodeGen/IslExprBuilder.cpp
> URL: http://llvm.org/viewvc/llvm-project/polly/trunk/lib/CodeGen/IslExprBuilder.cpp?rev=238929&r1=238928&r2=238929&view=diff
> ==============================================================================
> --- polly/trunk/lib/CodeGen/IslExprBuilder.cpp (original)
> +++ polly/trunk/lib/CodeGen/IslExprBuilder.cpp Wed Jun  3 10:14:58 2015
> @@ -295,6 +295,13 @@ Value *IslExprBuilder::createOpBin(__isl
>      Res = Builder.CreateNSWMul(LHS, RHS);
>      break;
>    case isl_ast_op_div:
> +    if (auto *Const = dyn_cast<ConstantInt>(RHS)) {
> +      auto &Val = Const->getValue();
> +      if (Val.isPowerOf2() && Val.isNonNegative()) {
> +        Res = Builder.CreateAShr(LHS, Val.ceilLogBase2(), "pexp.div.shr");
> +        break;
> +      }
> +    }
>      Res = Builder.CreateSDiv(LHS, RHS, "pexp.div");
>      break;
>    case isl_ast_op_pdiv_q: // Dividend is non-negative
> 
> Modified: polly/trunk/test/Isl/CodeGen/exprModDiv.ll
> URL: http://llvm.org/viewvc/llvm-project/polly/trunk/test/Isl/CodeGen/exprModDiv.ll?rev=238929&r1=238928&r2=238929&view=diff
> ==============================================================================
> --- polly/trunk/test/Isl/CodeGen/exprModDiv.ll (original)
> +++ polly/trunk/test/Isl/CodeGen/exprModDiv.ll Wed Jun  3 10:14:58 2015
> @@ -46,10 +46,8 @@
>  ; POW2:  %polly.access.A6 = getelementptr float, float* %A, i64 %pexp.pdiv_r
>  
>  ; A[i / 128]
> -; POW2:  %pexp.div = sdiv i64 %polly.indvar, 128
> +; POW2:  %pexp.div.shr = ashr i64 %polly.indvar, 7
>  ; POW2:  %polly.access.B8 = getelementptr float, float* %B, i64 %pexp.div
> -;
> -; FIXME: Make isl mark this as an udiv expression.
>  
>  ; #define floord(n,d) ((n < 0) ? (n - d + 1) : n) / d
>  ; A[p + 128 * floord(-p - 1, 128) + 128]
> @@ -62,8 +60,8 @@
>  ; POW2:  %polly.access.A10 = getelementptr float, float* %A, i64 %24
>  
>  ; A[p / 128]
> -; POW2:  %pexp.div12 = sdiv i64 %p, 128
> -; POW2:  %polly.access.B13 = getelementptr float, float* %B, i64 %pexp.div12
> +; POW2:  %pexp.div.shr12 = ashr i64 %p, 7
> +; POW2:  %polly.access.B13 = getelementptr float, float* %B, i64 %pexp.div.shr12
>  
>  target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
>  
> 
> 
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits

-- 

Johannes Doerfert
Researcher / PhD Student

Compiler Design Lab (Prof. Hack)
Saarland University, Computer Science
Building E1.3, Room 4.31

Tel. +49 (0)681 302-57521 : doerfert at cs.uni-saarland.de
Fax. +49 (0)681 302-3065  : http://www.cdl.uni-saarland.de/people/doerfert
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 213 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150603/3abefb79/attachment.sig>