[PATCH] D156026: [InstCombine] Contracting x^2 + 2*x*y + y^2 to (x + y)^2

[Christoph Stiller via Phabricator via llvm-commits]

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There's a good chance the floating point version needs some restrictions (like non-NaN etc.)
Also, I'm not familiar with how the tests work yet, so please let me know how to add and run them.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D156026

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp


Index: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1615,6 +1615,20 @@
         I, Builder.CreateIntrinsic(Intrinsic::ctpop, {I.getType()},
                                    {Builder.CreateOr(A, B)}));
 
+  // (x * x) + ((x << 1) + y) * y -> (x * y)^2
+  // which is:
+  // (x * x) + (2 * x * y) + (y * y) -> (x * y)^2
+  if (match(RHS, m_Mul(m_Value(A), m_Value(B))) && A == B) {
+    Value *C;
+    if (match(LHS, m_Mul(m_Add(m_Shl(m_Specific(A), m_SpecificInt(1)),
+                                 m_Value(C)),
+                          m_Value(B))) &&
+        B == C) {
+      Value *AB = Builder.CreateAdd(A, B);
+      return BinaryOperator::CreateMul(AB, AB, I.getName());
+    }
+  }
+
   if (Instruction *Res = foldBinOpOfDisplacedShifts(I))
     return Res;
 
@@ -1846,6 +1860,18 @@
     return Result;
   }
 
+  // (x * x) + ((2 * x) + y) * y -> (x * y)^2
+  // which is:
+  // (x * x) + (2 * x * y) + (y * y) -> (x * y)^2
+  if (match(RHS, m_FMul(m_Value(X), m_Value(Y))) && X == Y) {
+    Value *Z;
+    if (match(LHS, m_FMul(m_FAdd(m_FMul(m_Specific(X), m_SpecificFP(2.0)),
+                                 m_Value(Z)), m_Value(Y))) && Z == Y) {
+      Value *XY = Builder.CreateFAdd(X, Y);
+      return BinaryOperator::CreateFMulFMF(XY, XY, &I);
+    }
+  }
+
   return nullptr;
 }
 


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