[Thumb1] AND with a constant operand can be converted into BIC

So model the cost of materializing the constant operand C as the minimum of
C and ~C.

llvm-svn: 280929

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
index 2d44adc9951..48819335512 100644
--- a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
@@ -69,6 +69,10 @@ int ARMTTIImpl::getIntImmCost(unsigned Opcode, unsigned Idx, const APInt &Imm,
       Idx == 1)
     return 0;
 
+  if (Opcode == Instruction::And)
+      // Conversion to BIC is free, and means we can use ~Imm instead.
+      return std::min(getIntImmCost(Imm, Ty), getIntImmCost(~Imm, Ty));
+
   return getIntImmCost(Imm, Ty);
 }