[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

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);
 }
 

llvm/test/CodeGen/ARM/immcost.ll

@@ -19,3 +19,21 @@ true:
 ret:
   ret void
 }
+
+; CHECK: Function: h
+; CHECK-NOT: Collect constant i32 -193 from
+define void @h(i1 %cond, i32 %p, i32 %q) {
+entry:
+  %a = and i32 %p, 4294967103
+  call void @g(i32 %a)
+  br i1 %cond, label %true, label %ret
+
+true:
+  %b = and i32 %q, 4294967103
+  call void @g(i32 %b)
+  br label %ret
+
+ret:
+  ret void
+}
+