[llvm] r294650 - [InstCombine] allow (X * C2) << C1 --> X * (C2 << C1) for vectors

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Thu Feb  9 17:13:04 2017
New Revision: 294650

URL: http://llvm.org/viewvc/llvm-project?rev=294650&view=rev
Log:
[InstCombine] allow (X * C2) << C1 --> X * (C2 << C1) for vectors

This fold already existed for vectors but only when 'C1' was a splat
constant (but 'C2' could be any constant). 

There were no tests for any vector constants, so I'm adding a test
that shows non-splat constants for both operands.  

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp
    llvm/trunk/test/Transforms/InstCombine/apint-shift.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp?rev=294650&r1=294649&r2=294650&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp Thu Feb  9 17:13:04 2017
@@ -335,13 +335,6 @@ Instruction *InstCombiner::FoldShiftByCo
   assert(!Op1C->uge(TypeBits) &&
          "Shift over the type width should have been removed already");
 
-  // ((X*C1) << C2) == (X * (C1 << C2))
-  if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
-    if (BO->getOpcode() == Instruction::Mul && isLeftShift)
-      if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
-        return BinaryOperator::CreateMul(BO->getOperand(0),
-                                         ConstantExpr::getShl(BOOp, Op1));
-
   if (Instruction *FoldedShift = foldOpWithConstantIntoOperand(I))
     return FoldedShift;
 
@@ -604,12 +597,18 @@ Instruction *InstCombiner::visitShl(Bina
     }
   }
 
-  // (C1 << A) << C2 -> (C1 << C2) << A
-  Constant *C1, *C2;
-  Value *A;
-  if (match(Op0, m_OneUse(m_Shl(m_Constant(C1), m_Value(A)))) &&
-      match(Op1, m_Constant(C2)))
-    return BinaryOperator::CreateShl(ConstantExpr::getShl(C1, C2), A);
+  Constant *C1;
+  if (match(Op1, m_Constant(C1))) {
+    Constant *C2;
+    Value *X;
+    // (C2 << X) << C1 --> (C2 << C1) << X
+    if (match(Op0, m_OneUse(m_Shl(m_Constant(C2), m_Value(X)))))
+      return BinaryOperator::CreateShl(ConstantExpr::getShl(C2, C1), X);
+
+    // (X * C2) << C1 --> X * (C2 << C1)
+    if (match(Op0, m_Mul(m_Value(X), m_Constant(C2))))
+      return BinaryOperator::CreateMul(X, ConstantExpr::getShl(C2, C1));
+  }
 
   return nullptr;
 }

Modified: llvm/trunk/test/Transforms/InstCombine/apint-shift.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/apint-shift.ll?rev=294650&r1=294649&r2=294650&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/apint-shift.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/apint-shift.ll Thu Feb  9 17:13:04 2017
@@ -63,6 +63,8 @@ define i55 @test6(i55 %A) {
   ret i55 %C
 }
 
+; (X * C2) << C1 --> X * (C2 << C1)
+
 define i55 @test6a(i55 %A) {
 ; CHECK-LABEL: @test6a(
 ; CHECK-NEXT:    [[C:%.*]] = mul i55 %A, 6
@@ -73,6 +75,18 @@ define i55 @test6a(i55 %A) {
   ret i55 %C
 }
 
+; (X * C2) << C1 --> X * (C2 << C1)
+
+define <2 x i55> @test6a_vec(<2 x i55> %A) {
+; CHECK-LABEL: @test6a_vec(
+; CHECK-NEXT:    [[C:%.*]] = mul <2 x i55> %A, <i55 6, i55 48>
+; CHECK-NEXT:    ret <2 x i55> [[C]]
+;
+  %B = mul <2 x i55> %A, <i55 3, i55 12>
+  %C = shl <2 x i55> %B, <i55 1, i55 2>
+  ret <2 x i55> %C
+}
+
 define i29 @test7(i8 %X) {
 ; CHECK-LABEL: @test7(
 ; CHECK-NEXT:    ret i29 -1