JIT: Simple importer single-block forward substitution

[hez2010]

• Add a simple single-block forward substitution to propagate constants, typeof and FTN_ADDR in importer.
• Import calli with resolved FTN_ADDR as regular call to enable inlining

The branch name is calli-inlining but this is done mainly for enabling typeof propagation, while fptr propagation are enabled for free so I enabled inlining for them by the way.

Example:

unsafe
{
    var t1 = typeof(string);
    var t2 = typeof(int);
    delegate*<int, Type, int> ptr = &Foo;
    Console.WriteLine("Hello");
    Console.WriteLine(t1.IsValueType);
    Console.WriteLine(t2.IsValueType);
    Console.WriteLine(CallGenericReturn(ptr, 42, t1));
    Console.WriteLine(CallGenericReturn(ptr, 42, t2));
    delegate*<int, Type, int> ptr2 = &Bar;
    ptr2(42, t1);
}

static int Foo(int v, Type w)
{
    Console.WriteLine(v);
    Console.WriteLine(w.IsValueType);
    return v + 1;
}

static T Bar<T>(T v, Type w) where T : IBinaryInteger<T>
{
    Console.WriteLine(w.TypeHandle.Value);
    return v - T.One;
}

unsafe static T CallGenericReturn<T, U>(delegate*<T, U, T> del, T v, U w)
{
    return del(v, w);
}

Before:

G_M56640_IG01:  ;; offset=0x0000
       push     rbp
       push     r15
       push     rbx
       lea      rbp, [rsp+0x10]
						;; size=9 bbWeight=1 PerfScore 3.50
G_M56640_IG02:  ;; offset=0x0009
       mov      rdi, 0x73541C297D38      ; 'Hello'
       call     [System.Console:WriteLine(System.String)]
       mov      rbx, 0x73541C295020      ; 'System.String'
       mov      rdi, rbx
       call     [System.RuntimeType:IsValueTypeImpl():ubyte:this]
       mov      edi, eax
       call     [System.Console:WriteLine(ubyte)]
       mov      r15, 0x73541C297D10      ; 'System.Int32'
       mov      rdi, r15
       call     [System.RuntimeType:IsValueTypeImpl():ubyte:this]
       mov      edi, eax
       call     [System.Console:WriteLine(ubyte)]
       mov      edi, 42
       mov      rsi, rbx
       mov      rax, 0x73541F821470      ; function address
       call     rax
       mov      edi, eax
       call     [System.Console:WriteLine(int)]
       mov      edi, 42
       mov      rsi, r15
       mov      rax, 0x73541F821470      ; function address
       call     rax
       mov      edi, eax
       call     [System.Console:WriteLine(int)]
       mov      edi, 42
       mov      rsi, rbx
       mov      rax, 0x73541F821458      ; function address
       call     rax
       nop      
						;; size=147 bbWeight=1 PerfScore 34.75
G_M56640_IG03:  ;; offset=0x009C
       pop      rbx
       pop      r15
       pop      rbp
       ret      
						;; size=5 bbWeight=1 PerfScore 2.50

After:

G_M56640_IG01:  ;; offset=0x0000
       sub      rsp, 40
                                                ;; size=4 bbWeight=1 PerfScore 0.25
G_M56640_IG02:  ;; offset=0x0004
       mov      rcx, 0x21E8030F010      ; 'Hello'
       call     [System.Console:WriteLine(System.String)]
       xor      ecx, ecx
       call     [System.Console:WriteLine(ubyte)]
       mov      ecx, 1
       call     [System.Console:WriteLine(ubyte)]
       mov      ecx, 42
       call     [System.Console:WriteLine(int)]
       xor      ecx, ecx
       call     [System.Console:WriteLine(ubyte)]
       mov      ecx, 43
       call     [System.Console:WriteLine(int)]
       mov      ecx, 42
       call     [System.Console:WriteLine(int)]
       mov      ecx, 1
       call     [System.Console:WriteLine(ubyte)]
       mov      ecx, 43
       call     [System.Console:WriteLine(int)]
       mov      rcx, 0x7FFA75FE5928
       call     [System.Console:WriteLine(long)]
       nop
                                                ;; size=115 bbWeight=1 PerfScore 32.75
G_M56640_IG03:  ;; offset=0x0077
       add      rsp, 40
       ret
                                                ;; size=5 bbWeight=1 PerfScore 1.25

Another example:

Diff for Activator.CreateInstance<MyStruct>:

 G_M000_IG01:
-       push     rbx
+       sub      rsp, 40
-       sub      rsp, 48
        xor      eax, eax
-       mov      qword ptr [rsp+0x28], rax
+       mov      qword ptr [rsp+0x20], rax
 
 G_M000_IG02:
-       mov      rbx, 0xD1FFAB1E
-       mov      rcx, rbx
-       call     [System.RuntimeType:IsValueTypeImpl():ubyte:this]
-       test     eax, eax
+       lea      rdx, [rsp+0x20]
+       mov      rcx, 0xD1FFAB1E
+       call     [System.RuntimeType:CallDefaultStructConstructor(byref):this]
+       mov      rax, gword ptr [rsp+0x20]
-       je       SHORT G_M000_IG05
-
-G_M000_IG03:
-       xor      edx, edx
-       mov      gword ptr [rsp+0x28], rdx
-       lea      rdx, [rsp+0x28]
-       mov      rcx, rbx
-       call     [System.RuntimeType:CallDefaultStructConstructor(byref):this]
-       mov      rax, gword ptr [rsp+0x28]
-
-G_M000_IG04:
-       add      rsp, 48
-       pop      rbx
-       ret
-
-G_M000_IG05:
-       mov      rcx, rbx
-       call     [System.RuntimeType:CreateInstanceOfT():System.Object:this]
-       nop
 
-G_M000_IG06:
+       add      rsp, 40
-       add      rsp, 48
-       pop      rbx
        ret

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[hez2010]

@MihuBot

[EgorBo]

I guess this PR hits the same issues as Andy mentioned in #98380 (comment) from obvious issues is e.g. lack of "is address exposed" check. Also you sort of rely that def always comes before use in execution order

[hez2010]

lack of "is address exposed" check

Resolved.

Also you sort of rely that def always comes before use in execution order

Yes. If there's a use coming before the def like in a cycle, the def would be in another BB, in this case there won't be any substitution for the use as we restrict both the def and use to present in a single BB.

[hez2010]

Diffs

Tests are passing.

This PR doesn't handle typeof stored into fields.

[hez2010]

@MihuBot