Consider the following example:
static void Main(string[] args)
{
Console.WriteLine((int)'3');
for (int i = 0; i < 100; i++)
{
foo('3');
Thread.Sleep(16);
}
}
[MethodImpl(MethodImplOptions.NoInlining)]
static ulong foo(int x)
{
if (x == '1')
return 1;
if (x == '2')
return 2;
if (x == '3')
return 3;
return 0;
}and run it with Dynamic PGO, codegen for foo:
; Assembly listing for method foo(int):ulong
; Tier-1 compilation
; optimized using profile data
; with Dynamic PGO: edge weights are valid, and fgCalledCount is 4
G_M55197_IG01: ;; offset=0000H
;; size=0 bbWeight=1 PerfScore 0.00
G_M55197_IG02: ;; offset=0000H
83F931 cmp ecx, 49 ; '1'
7413 je SHORT G_M55197_IG06
83F932 cmp ecx, 50 ; '2'
7414 je SHORT G_M55197_IG08
83F933 cmp ecx, 51 ; '3'
7506 jne SHORT G_M55197_IG04
B803000000 mov eax, 3
;; size=20 bbWeight=1 PerfScore 4.00
G_M55197_IG03: ;; offset=0014H
C3 ret
;; size=1 bbWeight=1 PerfScore 1.00
G_M55197_IG04: ;; offset=0015H
33C0 xor eax, eax
;; size=2 bbWeight=0 PerfScore 0.00
G_M55197_IG05: ;; offset=0017H
C3 ret
;; size=1 bbWeight=0 PerfScore 0.00
G_M55197_IG06: ;; offset=0018H
B801000000 mov eax, 1
;; size=5 bbWeight=0 PerfScore 0.00
G_M55197_IG07: ;; offset=001DH
C3 ret
;; size=1 bbWeight=0 PerfScore 0.00
G_M55197_IG08: ;; offset=001EH
B802000000 mov eax, 2
;; size=5 bbWeight=0 PerfScore 0.00
G_M55197_IG09: ;; offset=0023H
C3 ret
;; size=1 bbWeight=0 PerfScore 0.00I'd expected it to re-order checks and make if (x == '3') first one
cc @AndyAyersMS @jakobbotsch
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Consider the following example:
and run it with Dynamic PGO, codegen for
foo:I'd expected it to re-order checks and make
if (x == '3')first onecc @AndyAyersMS @jakobbotsch
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