Inlined struct copies via params, returns and assignment not elided #12219
Description
As seen in ValueTaskAwaiter from dotnet/coreclr#22735, dotnet/coreclr#22738 wasn't a specific issue for it with simple repo so opening this.
using System.Runtime.CompilerServices;
class Program
{
static void Main(string[] args)
{
InlinedAssignment();
InlinedCtor();
}
[MethodImpl(MethodImplOptions.NoInlining)]
static long InlinedAssignment()
{
var s = CreateLargeStruct();
s = GetLargeStruct(s);
return s.l3;
}
[MethodImpl(MethodImplOptions.NoInlining)]
static long InlinedCtor()
{
var s = new LargeStruct2(CreateLargeStruct());
return s._largeStruct.l3;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
static LargeStruct GetLargeStruct(LargeStruct l) => l;
[MethodImpl(MethodImplOptions.NoInlining)]
static LargeStruct CreateLargeStruct() => new LargeStruct();
}
readonly struct LargeStruct
{
public readonly long l0;
public readonly long l1;
public readonly long l2;
public readonly long l3;
}
readonly struct LargeStruct2
{
public readonly LargeStruct _largeStruct;
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public LargeStruct2(LargeStruct largeStruct)
{
_largeStruct = largeStruct;
}
}Produces
; Assembly listing for method Program:InlinedAssignment():long
; V00 OutArgs [V00 ] ( 1, 1 ) lclBlk (32) [rsp+0x00] "OutgoingArgSpace"
; V01 tmp1 [V01 ] ( 2, 4 ) struct (32) [rsp+0x48] do-not-enreg[XSB] addr-exposed "struct address for call/obj"
;* V02 tmp2 [V02 ] ( 0, 0 ) struct (32) zero-ref "struct address for call/obj"
; V03 tmp3 [V03 ] ( 2, 4 ) struct (32) [rsp+0x28] do-not-enreg[XSB] addr-exposed "Inlining Arg"
;* V04 tmp4 [V04 ] ( 0, 0 ) long -> zero-ref V02.l0(offs=0x00) P-INDEP "field V02.l0 (fldOffset=0x0)"
;* V05 tmp5 [V05 ] ( 0, 0 ) long -> zero-ref V02.l1(offs=0x08) P-INDEP "field V02.l1 (fldOffset=0x8)"
;* V06 tmp6 [V06 ] ( 0, 0 ) long -> zero-ref V02.l2(offs=0x10) P-INDEP "field V02.l2 (fldOffset=0x10)"
; V07 tmp7 [V07,T01] ( 2, 2 ) long -> rax V02.l3(offs=0x18) P-INDEP "field V02.l3 (fldOffset=0x18)"
; V08 tmp8 [V08,T00] ( 3, 6 ) byref -> rax "BlockOp address local"
; Lcl frame size = 104
G_M60975_IG01:
4883EC68 sub rsp, 104
C5F877 vzeroupper
G_M60975_IG02:
488D4C2448 lea rcx, bword ptr [rsp+48H]
E8BF67FFFF call Program:CreateLargeStruct():struct
C5FA6F442448 vmovdqu xmm0, qword ptr [rsp+48H]
C5FA7F442428 vmovdqu qword ptr [rsp+28H], xmm0
C5FA6F442458 vmovdqu xmm0, qword ptr [rsp+58H]
C5FA7F442438 vmovdqu qword ptr [rsp+38H], xmm0
488D442428 lea rax, bword ptr [rsp+28H]
488B10 mov rdx, qword ptr [rax]
488B4018 mov rax, qword ptr [rax+24]
G_M60975_IG03:
4883C468 add rsp, 104
C3 ret
; Total bytes of code 58, prolog size 7 for method Program:InlinedAssignment():longand
; Assembly listing for method Program:InlinedCtor():long
; V00 OutArgs [V00 ] ( 1, 1 ) lclBlk (32) [rsp+0x00] "OutgoingArgSpace"
; V01 tmp1 [V01,T00] ( 2, 4 ) struct (32) [rsp+0x68] do-not-enreg[SFB] "NewObj constructor temp"
; V02 tmp2 [V02 ] ( 2, 4 ) struct (32) [rsp+0x48] do-not-enreg[XSB] addr-exposed "struct address for call/obj"
; V03 tmp3 [V03,T01] ( 2, 4 ) struct (32) [rsp+0x28] do-not-enreg[SB] "Inlining Arg"
;
; Lcl frame size = 136
G_M31928_IG01:
4881EC88000000 sub rsp, 136
C5F877 vzeroupper
G_M31928_IG02:
488D4C2448 lea rcx, bword ptr [rsp+48H]
E8BCFFFFFF call Program:CreateLargeStruct():struct
C5FA6F442448 vmovdqu xmm0, qword ptr [rsp+48H]
C5FA7F442428 vmovdqu qword ptr [rsp+28H], xmm0
C5FA6F442458 vmovdqu xmm0, qword ptr [rsp+58H]
C5FA7F442438 vmovdqu qword ptr [rsp+38H], xmm0
C5FA6F442428 vmovdqu xmm0, qword ptr [rsp+28H]
C5FA7F442468 vmovdqu qword ptr [rsp+68H], xmm0
C5FA6F442438 vmovdqu xmm0, qword ptr [rsp+38H]
C5FA7F442478 vmovdqu qword ptr [rsp+78H], xmm0
488B842480000000 mov rax, qword ptr [rsp+80H]
G_M31928_IG03:
4881C488000000 add rsp, 136
C3 ret
; Total bytes of code 84, prolog size 10 for method Program:InlinedCtor():longSome of these copies could be skipped?
/cc @AndyAyersMS @mikedn @stephentoub @jkotas
category:cq
theme:structs
skill-level:expert
cost:large