rts: Ensure that XMM registers are preserved on Win64
Previously we only preserved the bottom 64-bits of the callee-saved 128-bit XMM registers, in violation of the Win64 calling convention. Fix this.
Fixes #21465 (closed).
Previously we only preserved the bottom 64-bits of the callee-saved 128-bit XMM registers, in violation of the Win64 calling convention. Fix this.
Fixes #21465 (closed).