+ // Check for NOOP conversions.
+ if (SrcLT.first == DstLT.first &&
+ SrcLT.second.getSizeInBits() == DstLT.second.getSizeInBits()) {
+
+ // Bitcast between types that are legalized to the same type are free.
+ if (Opcode == Instruction::BitCast || Opcode == Instruction::Trunc)
+ return 0;
+ }
+
+ if (Opcode == Instruction::Trunc &&
+ TLI->isTruncateFree(SrcLT.second, DstLT.second))
+ return 0;
+
+ if (Opcode == Instruction::ZExt &&
+ TLI->isZExtFree(SrcLT.second, DstLT.second))
+ return 0;
+
+ // If the cast is marked as legal (or promote) then assume low cost.
+ if (TLI->isOperationLegalOrPromote(ISD, DstLT.second))
+ return 1;
+