llvm dev - Nov 2015 - [PATCH] patch for missed constantFold optimization in InstCombine

Hi,
Any reviewers for this patch ? Any suggestions ?
Opt tool's output for this ll before and after the patch is also attached.

Thanks,
Tejas

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Budukh,
Tejas via llvm-dev
Sent: Friday, November 06, 2015 9:43 AM
To: llvm-dev at lists.llvm.org
Subject: [llvm-dev] [PATCH] patch for missed constantFold optimization in
InstCombine

Hi All,
llvm::ConstantFoldCompareInstOperands misses an optimization when it tries to
constantFold a compare instruction containing addrspacecast instead of
combination of ptrtoint and inttoptr. Adding the patched code snippet in the
code would enable the pass to handle addrspacecast and constantFold the missing
cases.
Attached is the .ll file for the reproducer. Let me know if there are any
suggestions/comments or I can commit the patch.

Patched code :
Index: ConstantFolding.cpp
==================================================================diff --git
a/llvm/trunk/lib/Analysis/ConstantFolding.cpp
b/llvm/trunk/lib/Analysis/ConstantFolding.cpp
--- a/llvm/trunk/lib/Analysis/ConstantFolding.cpp            (revision 252222)
+++ b/llvm/trunk/lib/Analysis/ConstantFolding.cpp        (working copy)
@@ -1137,6 +1137,12 @@
           return ConstantFoldCompareInstOperands(Predicate, C, Null, DL, TLI);
         }
       }
+
+      if (CE0->getOpcode() == Instruction::AddrSpaceCast) {
+          Constant *C = CE0->getOperand(0);
+          Constant *Null = Constant::getNullValue(C->getType());
+          return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI);
+      }
     }

     if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) {


Thanks,
Tejas
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Please send patches to llvm-commits as per our policy:
http://llvm.org/docs/DeveloperPolicy.html

Also, your test-case needs to use FileCheck.

On Tue, Nov 10, 2015 at 1:58 PM, Budukh, Tejas via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi,
>
> Any reviewers for this patch ? Any suggestions ?
>
> Opt tool’s output for this ll before and after the patch is also attached.
>
>
>
> Thanks,
>
> Tejas
>
>
>
> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of
*Budukh,
> Tejas via llvm-dev
> *Sent:* Friday, November 06, 2015 9:43 AM
> *To:* llvm-dev at lists.llvm.org
> *Subject:* [llvm-dev] [PATCH] patch for missed constantFold optimization
> in InstCombine
>
>
>
> Hi All,
>
> llvm::ConstantFoldCompareInstOperands misses an optimization when it tries
> to constantFold a compare instruction containing addrspacecast instead of
> combination of ptrtoint and inttoptr. Adding the patched code snippet in
> the code would enable the pass to handle addrspacecast and constantFold the
> missing cases.
>
> Attached is the .ll file for the reproducer. Let me know if there are any
> suggestions/comments or I can commit the patch.
>
>
>
> Patched code :
>
> Index: ConstantFolding.cpp
>
> ==================================================================>
> diff --git a/llvm/trunk/lib/Analysis/ConstantFolding.cpp
> b/llvm/trunk/lib/Analysis/ConstantFolding.cpp
>
> --- a/llvm/trunk/lib/Analysis/ConstantFolding.cpp            (revision
> 252222)
>
> +++ b/llvm/trunk/lib/Analysis/ConstantFolding.cpp        (working copy)
>
> @@ -1137,6 +1137,12 @@
>
>            return ConstantFoldCompareInstOperands(Predicate, C, Null, DL,
> TLI);
>
>          }
>
>        }
>
> +
>
> +      if (CE0->getOpcode() == Instruction::AddrSpaceCast) {
>
> +          Constant *C = CE0->getOperand(0);
>
> +          Constant *Null = Constant::getNullValue(C->getType());
>
> +          return ConstantFoldCompareInstOperands(Predicate, C, Null, TD,
> TLI);
>
> +      }
>
>      }
>
>
>
>      if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) {
>
>
>
>
>
> Thanks,
>
> Tejas
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
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