<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On 18 June 2014 06:19, suyog <span dir="ltr"><<a href="mailto:suyog.sarda@samsung.com" target="_blank">suyog.sarda@samsung.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">

<br>
Hi Nick,<br>
<br>
Added supporting testcase.<br>
<br>
Please if you could commit it for me if it looks<br>
good to you.<br></blockquote><div><br></div><div>Not yet, sorry. It needs a test that ensures that "opt -instsimplify" *is* doing the new simplification we just taught it. You can keep the test you wrote too if you like. Also, using "grep" is old-style, please use FileCheck. For example:</div>

<div><br></div><div><div>define i32 @test1(i32 %x) {</div><div>; CHECK-LABEL: @test1</div><div>; CHECK-NOT: ashr</div><div>  %o = and i32 %x, 1</div><div>  %n = add i32 %o, -1</div><div>  %t = ashr i32 %n, 17</div><div>  ret i32 %t</div>

<div>}</div></div><div><br></div><div>Nick</div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">


<div class="">Thanks,<br>
Suyog<br>
<br>
<a href="http://reviews.llvm.org/D4102" target="_blank">http://reviews.llvm.org/D4102</a><br>
<br>
Files:<br>
  lib/Analysis/InstructionSimplify.cpp<br>
  lib/Transforms/InstCombine/InstCombineShifts.cpp<br>
</div>  test/Transforms/InstSimplify/ashr-nop.ll<br>
<div><div class="h5"><br>
Index: lib/Analysis/InstructionSimplify.cpp<br>
===================================================================<br>
--- lib/Analysis/InstructionSimplify.cpp<br>
+++ lib/Analysis/InstructionSimplify.cpp<br>
@@ -1436,6 +1436,11 @@<br>
       cast<OverflowingBinaryOperator>(Op0)->hasNoSignedWrap())<br>
     return X;<br>
<br>
+  // Arithmetic shifting an all-sign-bit value is a no-op.<br>
+  unsigned NumSignBits = ComputeNumSignBits(Op0);<br>
+  if (NumSignBits == Op0->getType()->getScalarSizeInBits())<br>
+    return Op0;<br>
+<br>
   return nullptr;<br>
 }<br>
<br>
Index: lib/Transforms/InstCombine/InstCombineShifts.cpp<br>
===================================================================<br>
--- lib/Transforms/InstCombine/InstCombineShifts.cpp<br>
+++ lib/Transforms/InstCombine/InstCombineShifts.cpp<br>
@@ -820,10 +820,5 @@<br>
                         APInt::getSignBit(I.getType()->getScalarSizeInBits())))<br>
     return BinaryOperator::CreateLShr(Op0, Op1);<br>
<br>
-  // Arithmetic shifting an all-sign-bit value is a no-op.<br>
-  unsigned NumSignBits = ComputeNumSignBits(Op0);<br>
-  if (NumSignBits == Op0->getType()->getScalarSizeInBits())<br>
-    return ReplaceInstUsesWith(I, Op0);<br>
-<br>
   return nullptr;<br>
 }<br>
</div></div>Index: test/Transforms/InstSimplify/ashr-nop.ll<br>
===================================================================<br>
--- test/Transforms/InstSimplify/ashr-nop.ll<br>
+++ test/Transforms/InstSimplify/ashr-nop.ll<br>
@@ -0,0 +1,8 @@<br>
+; RUN: opt < %s -instsimplify -S | not grep ashr<br>
+<br>
+define i32 @foo(i32 %x) {<br>
+  %o = and i32 %x, 1<br>
+  %n = add i32 %o, -1<br>
+  %t = ashr i32 %n, 17<br>
+  ret i32 %t<br>
+}<br>
</blockquote></div><br></div></div>