Move ashr optimization from InstCombineShift to InstSimplify.

Refactor code, no functionality change, test case moved from instcombine to instsimplify. Differential Revision: http://reviews.llvm.org/D4102 llvm-svn: 213231
llvm · Jul 17, 2014 · 6886241 · 6886241
1 parent ac6e39c
commit 6886241
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Showing 4 changed files with 15 additions and 13 deletions.
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1346,6 +1346,11 @@ static Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
       cast<OverflowingBinaryOperator>(Op0)->hasNoSignedWrap())
     return X;
 
+  // Arithmetic shifting an all-sign-bit value is a no-op.
+  unsigned NumSignBits = ComputeNumSignBits(Op0);
+  if (NumSignBits == Op0->getType()->getScalarSizeInBits())
+    return Op0;
+
   return nullptr;
 }
 

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
@@ -815,10 +815,5 @@ Instruction *InstCombiner::visitAShr(BinaryOperator &I) {
                         APInt::getSignBit(I.getType()->getScalarSizeInBits())))
     return BinaryOperator::CreateLShr(Op0, Op1);
 
-  // Arithmetic shifting an all-sign-bit value is a no-op.
-  unsigned NumSignBits = ComputeNumSignBits(Op0);
-  if (NumSignBits == Op0->getType()->getScalarSizeInBits())
-    return ReplaceInstUsesWith(I, Op0);
-
   return nullptr;
 }
diff --git a/llvm/test/Transforms/InstCombine/ashr-nop.ll b/llvm/test/Transforms/InstCombine/ashr-nop.ll
diff --git a/llvm/test/Transforms/InstSimplify/ashr-nop.ll b/llvm/test/Transforms/InstSimplify/ashr-nop.ll
@@ -0,0 +1,10 @@
+; RUN: opt < %s -instsimplify -S | FileCheck %s
+
+; CHECK-LABEL: @foo
+; CHECK-NOT: ashr
+define i32 @foo(i32 %x) {
+ %o = and i32 %x, 1
+ %n = add i32 %o, -1
+ %t = ashr i32 %n, 17
+ ret i32 %t
+}