RFR(XS): 8149543: range check CastII nodes should not be split through Phi

[Berg, Michael C]

Looks good to me.

Regards,
Michael

-----Original Message-----
From: hotspot-compiler-dev [mailto:hotspot-compiler-dev-bounces at openjdk.java.net] On Behalf Of Roland Westrelin
Sent: Wednesday, February 10, 2016 5:12 AM
To: hotspot compiler
Subject: RFR(XS): 8149543: range check CastII nodes should not be split through Phi

http://cr.openjdk.java.net/~roland/8149543/webrev.00/

Reported by Michael Berg for vectorization optimizations. 
In cases like this: 

  public static float sumListReduction(float[] a, float[] b, float[] c, float[] d, float total, int process_len) 
  { 
    for(int i = 0; i < process_len; i++) 
    { 
      d[i]= (a[i] * b[i]) + (a[i] * c[i]) + (b[i] * c[i]); 
    } 

    total += d[0]; 
    total += d[process_len-1]; 
    return total; 
  } 

Range check CastII nodes are split through the loop induction Phi which causes new Phis to be created that are unrelated to the trip Phi and prevent further optimizations: 

Phi 735 718 43 384 [ 784 384 ] bci = 10 debug_orig = dump_spec = #int:>=1:www #tripcount debug_idx = 17200735 line = 32 type = int: 

Phi 921 718 43 384 [ 727 ] bci = 16 debug_orig = dump_spec = #int:1..max-1:www debug_idx = 23800921 line = 32 type = int: 

I propose we simply don’t split range check CastII nodes through Phis.

Roland.