[llvm-commits] [llvm] r83761 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/mul.ll

[Chris Lattner]

Author: lattner
Date: Sun Oct 11 02:53:15 2009
New Revision: 83761

URL: http://llvm.org/viewvc/llvm-project?rev=83761&view=rev
Log:
implement rdar://7293527, a trivial instcombine that llvm-gcc
gets but clang doesn't, because it is implemented in GCC's
fold routine.

Modified:
    llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
    llvm/trunk/test/Transforms/InstCombine/mul.ll

Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=83761&r1=83760&r2=83761&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Sun Oct 11 02:53:15 2009
@@ -2661,7 +2661,7 @@
   if (isa<UndefValue>(I.getOperand(1)))              // undef * X -> 0
     return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
 
-  // Simplify mul instructions with a constant RHS...
+  // Simplify mul instructions with a constant RHS.
   if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
     if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
 
@@ -2765,9 +2765,20 @@
     }
   }
 
+  /// i1 mul -> i1 and.
   if (I.getType() == Type::getInt1Ty(*Context))
     return BinaryOperator::CreateAnd(Op0, I.getOperand(1));
 
+  // X*(1 << Y) --> X << Y
+  // (1 << Y)*X --> X << Y
+  {
+    Value *Y;
+    if (match(Op0, m_Shl(m_One(), m_Value(Y))))
+      return BinaryOperator::CreateShl(I.getOperand(1), Y);
+    if (match(I.getOperand(1), m_Shl(m_One(), m_Value(Y))))
+      return BinaryOperator::CreateShl(Op0, Y);
+  }
+  
   // If one of the operands of the multiply is a cast from a boolean value, then
   // we know the bool is either zero or one, so this is a 'masking' multiply.
   // See if we can simplify things based on how the boolean was originally

Modified: llvm/trunk/test/Transforms/InstCombine/mul.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/mul.ll?rev=83761&r1=83760&r2=83761&view=diff

==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/mul.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/mul.ll Sun Oct 11 02:53:15 2009
@@ -88,3 +88,11 @@
         %b = mul <16 x i8> %a, zeroinitializer
         ret <16 x i8> %b
 }
+
+; rdar://7293527
+define i32 @test15(i32 %A, i32 %B) {
+entry:
+  %shl = shl i32 1, %B
+  %m = mul i32 %shl, %A
+  ret i32 %m
+}