Implement computed goto dispatch for the CoreCLR interpreter

[BrzVlad]

Instead of making each opcode dispatch to the loop start where we switch on the opcode, we transform every switch case into a label, we let the compiler statically populate the s_dispatchTable which maps each opcode to the label address. This makes opcode dispatch a simple load + branch to the label address from this table. This makes the interpreter 25% faster.

It is unclear whether this has any impact on wasm. Likely not, because wasm has control flow limitations that make random branches impossible.

As an additional optimization, we avoid saving pFrame->ip for each opcode. Removing this can improve execution speed by around 3%. Instead we explicitly save pFrame->ip in opcodes that can trigger GC or throw exception. Add InterpThrow helper to ensure pFrame->ip is set before all throws.

[Copilot]

Copilot wasn't able to review any files in this pull request.

[BrzVlad]

/azp run runtime-interpreter

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[BrzVlad]

/azp run runtime-libraries-interpreter

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[BrzVlad]

Assembly before

// INTOP_NEXT
0x105260a0c: ldr    w23, [x28, #0xc]!   // x28 = ip, load the next opcode
0x105260a10: cmp    w23, #0x15f         // check for the default branch
0x105260a14: b.ls   0x10525e034
0x105260a18: b      0x10526295c

// Loop start
0x10525e034: mov    w8, w23
0x10525e038: adrp   x11, 414            // rather long switch dispatch
0x10525e03c: add    x11, x11, #0x624
0x10525e040: adr    x9, 0x10525e008
0x10525e044: ldrh   w10, [x11, x8, lsl #1]
0x10525e048: add    x9, x9, x10, lsl #2
0x10525e04c: br     x9

Assembly after

// INTOP_NEXT
0x1051f63e0: ldr    w23, [x27, #0x8]!       // x27 = ip, load the next opcode
0x1051f63e4: ldr    x8, [x22, x23, lsl #3]  // x22 = s_dispatchTable, load label of next
0x1051f63e8: br     x8                      // dispatch