[Wasm/Ryujit] Fix if stack depth; fix pep call ordering

[AndyAyersMS]

Account for additional control flow stack depth added during codegen when using if/end.

Fix argument eval ordering for PEP calls so the PEP is pushed as the last arg, and then pushed and indirected to get the function index.

[Copilot]

Pull request overview

This PR updates the Wasm RyuJIT backend to better handle Wasm control-flow depth for generated if/end blocks and to adjust Portable Entry Point indirect-call lowering so the PEP argument is evaluated before the final call target load.

Changes:

• Adds Wasm if/end emission helpers that track extra control-flow depth for branch depth calculation.
• Replaces several direct if/end emissions with the new helpers.
• Reorders PEP call target lowering so the indirect call target is pushed immediately before the call.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/coreclr/jit/lowerwasm.cpp	Reorders PEP control-expression load placement before the call.
src/coreclr/jit/codegenwasm.cpp	Tracks extra Wasm control-flow depth and routes generated if/end through helpers.
src/coreclr/jit/codegen.h	Adds Wasm codegen state and helper declarations.

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[AndyAyersMS]

FYI @dotnet/jit-contrib
@kg PTAL

For a PEP call we were emitting the control target before the pep instead of after. For late-introduced control flow we were not accounting for the extra depth.

@davidwrighton this should fix the two issues you were seeing.

Seems like we should be able to use a wasm local for the pep / target instead of storing it on the shadow stack, but will tackle that later. Eg the sequence is now

 ;; set up shadow stack addr
IN0020: 000050      local.get 0
IN0021: 000052      i32.const 8      ;; V04
IN0022: 000054      i32.add    

;; fetch pep     
IN0023: 000055      global.get 1
IN0024: 000057      i32.const_address 4611686018431713328
IN0025: 00005D      i32.add
IN0026: 00005E      i32.load 0 0

;; save pep to shadow stack
IN0027: 000061      i32.store 0 0

;;; set up pep arg
IN0028: 000064      local.get 0
IN0029: 000066      i32.load 0 8      ;; V04

;; set up function index
IN002a: 000069      local.get 0
IN002b: 00006B      i32.load 0 8      ;; V04
IN002c: 00006E      i32.load 0 0

;; call
IN002d: 000071      call_indirect 4611686018431713336 0      ;; CORINFO_HELP_OVERFLOW

and it could be simply

;; fetch pep     
IN0023: 000055      global.get 1
IN0024: 000057      i32.const_address 4611686018431713328
IN0025: 00005D      i32.add
IN0026: 00005E      i32.load 0 0

;; save it to temp and leave on stack (sets up pep arg)
                    i32.tee $temp

;; set up function index

                    local.get $temp
                    i32.load

;; call
                    call_indirect ....

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.