During the investigation of #88292 I found that NativeAOT/ARM64 and R2R never generates frameless methods. A typical app ends up with >30% of methods with simple frame prolog/epilog with no callee saved registers or extra stack space. Most of these methods are very likely to be leaf methods which can be frameless.
For example, take this simple method:
int Square(int num) { return num * num; }NativeAOT generates the following code:
Program:Square(int):int (FullOpts):
stp fp, lr, [sp, #-0x10]!
mov fp, sp
mul w0, w0, w0
ldp fp, lr, [sp], #0x10
ret lrAn optimizing C compiler (clang -O) generates:
square: // @square
mul w0, w0, w0
ret
Not only the code size is significantly smaller, but it also saves a lot of space for the unwinding information.
During the investigation of #88292 I found that NativeAOT/ARM64 and R2R never generates frameless methods. A typical app ends up with >30% of methods with simple frame prolog/epilog with no callee saved registers or extra stack space. Most of these methods are very likely to be leaf methods which can be frameless.
For example, take this simple method:
NativeAOT generates the following code:
An optimizing C compiler (
clang -O) generates:Not only the code size is significantly smaller, but it also saves a lot of space for the unwinding information.