[llvm] r265801 - [InstCombine] Add a peephole for redundant assumes

[David Majnemer via llvm-commits]

Author: majnemer
Date: Fri Apr  8 11:37:12 2016
New Revision: 265801

URL: http://llvm.org/viewvc/llvm-project?rev=265801&view=rev
Log:
[InstCombine] Add a peephole for redundant assumes

Two or more identical assumes are occasionally next to each other in a
basic block.
While our generic machinery will turn a redundant assume into a no-op,
it is not super cheap.
We can perform a simpler check to achieve the same result for this case.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp?rev=265801&r1=265800&r2=265801&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Fri Apr  8 11:37:12 2016
@@ -1943,11 +1943,16 @@ Instruction *InstCombiner::visitCallInst
     break;
   }
   case Intrinsic::assume: {
+    Value *IIOperand = II->getArgOperand(0);
+    // Remove an assume if it is immediately followed by an identical assume.
+    if (match(II->getNextNode(),
+              m_Intrinsic<Intrinsic::assume>(m_Specific(IIOperand))))
+      return eraseInstFromFunction(CI);
+
     // Canonicalize assume(a && b) -> assume(a); assume(b);
     // Note: New assumption intrinsics created here are registered by
     // the InstCombineIRInserter object.
-    Value *IIOperand = II->getArgOperand(0), *A, *B,
-          *AssumeIntrinsic = II->getCalledValue();
+    Value *AssumeIntrinsic = II->getCalledValue(), *A, *B;
     if (match(IIOperand, m_And(m_Value(A), m_Value(B)))) {
       Builder->CreateCall(AssumeIntrinsic, A, II->getName());
       Builder->CreateCall(AssumeIntrinsic, B, II->getName());