NASM 2.05 based x86 Instruction Reference[ch069]
A.5.49 CVTSS2SD: Scalar Single-Precision FP to Scalar Double-Precision FP Conversion CVTSS2SD xmm1,xmm2/mem32 ; F3 0F 5A /r [WILLAMETTE,SSE2] CVTSS2SD converts a single-precision FP value from the source operand to a double-precision FP value in the low quadword of the destination operand. The upper quadword is left unchanged. The destination operand is an XMM register. The source can be either an XMM register or a 32-bit memory location. If the source is a register, the input value is contained in the low doubleword. For more details of this instruction, see the Intel Processor manuals.