Couldn't find any related issue and decided to file it:
unsafe void DeadStore1(int* array)
{
*array = 1;
*array = 2;
*array = 3;
}
void DeadStore2(ref int x)
{
x = 1;
x = 2;
x = 3;
}
void DeadStore3(int[] array)
{
if (0 < (uint)array.Length)
{
array[0] = 1;
array[0] = 2;
array[0] = 3;
}
}
Codegen:
; DeadStore1(long):this
G_M36731_IG01:
G_M36731_IG02:
mov dword ptr [rdx], 1
mov dword ptr [rdx], 2
mov dword ptr [rdx], 3
G_M36731_IG03:
ret
; Total bytes of code: 19
; DeadStore2(byref):this
G_M42680_IG01:
G_M42680_IG02:
mov dword ptr [rdx], 1
mov dword ptr [rdx], 2
mov dword ptr [rdx], 3
G_M42680_IG03:
ret
; Total bytes of code: 19
; DeadStore3(System.Int32[]):this
G_M18892_IG01:
G_M18892_IG02:
mov eax, dword ptr [rdx+8]
test eax, eax
je SHORT G_M18892_IG04
G_M18892_IG03: ;; bbWeight=0.50
mov dword ptr [rdx+16], 1
mov dword ptr [rdx+16], 2
mov dword ptr [rdx+16], 3
G_M18892_IG04:
ret
; Total bytes of code: 29
In none of these cases dead stores were eliminated.
Is it a known Value Numbering limitation?
Mono-LLVM:
00000000000b10 <Program_DeadStore1_int_>: b10: c7 06 03 00 00 00 mov DWORD PTR [rsi],0x3 b16: c3 ret 0000000000000b20 <Program_DeadStore2_int_>: b20: c7 06 03 00 00 00 mov DWORD PTR [rsi],0x3 b26: c3 ret 0000000000000b30 <Program_DeadStore3_int__>: b30: 83 7e 18 00 cmp DWORD PTR [rsi+0x18],0x0 b34: 74 07 je b3d <Program_DeadStore3_int__+0xd> b36: c7 46 20 03 00 00 00 mov DWORD PTR [rsi+0x20],0x3 b3d: c3 ret
category:cq
theme:optimization
skill-level:intermediate
cost:small
impact:small
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