>>73
The quirks in x86 make things harder for compilers, assembly programmers, debuggers, optimizers, OS developers, hardware designers, and hardware testers, and result in hardware that does less while using more power and transistors. Imagine if the billions of dollars that went into x86 instead went into a better architecture. Instead of instructions like DAA and LAHF (both one byte even though they're rarely used), there could be instructions that compilers can actually use. CALL instructions in x86 often need to be followed by a wasteful ADD to adjust the stack, which makes them longer than calls in RISCs. Branch-and-link is better for functional languages because it doesn't impose a stack. A conditional branch-and-link takes 4 bytes in RISC instruction sets. It's more general and more powerful, while also being shorter. Instead of looking at how the compiler can use instructions which ``arose from practical considerations'' in the 70's for Z80 compatibility, look at the types of instructions compilers need. Instead of having x87, MMX, and SSE with huge overlap in functionality, use a single vector/FP architecture.
An elegant instruction set makes for smaller compilers, easier debugging, easier assembly programming, and easier implementation. The last one seems to be the real reason for why Intel keeps pushing x86. Anyone can make a MIPS or ARM, but x86 has so many quirks and kludges that building it from scratch is almost impossible (not to mention that most of them will never be used). There are 4 security rings when everybody only uses 2, partial flag updates, ugly formats for internal structures, Task State Segments with limited hardware task switching, Call Gates, MSRs, SMM, irregular instructions (DIV, string instructions, so many others), encodable instructions that signal a GPF because they exceed 15 bytes, multiple prefixes with undefined behavior, and so many other ``features'' that it would take less time to design an instruction set and compiler than for a third party to implement x86 (even assuming they are able to license the patents from Intel).