Code comparison between C1 and C2

c1-result.txt

C1

$ ~/jdk1.7.0-b147/fastdebug/bin/java -XX:CompileOnly=gvnex::doHashSum -XX:+PrintLIR -client gvnex
VM option 'CompileOnly=gvnex::doHashSum'
VM option '+PrintLIR'
CompileOnly: compileonly *gvnex*.doHashSum
LIR:
B1 [0, 0] sux: B0 
__id_Instruction___________________________________________
   0 label [label:0x939c62c]
   2 std_entry 
     move [ecx|L] [stack:3|L] 

B0 std [0, 68] preds: B1 
__id_Instruction___________________________________________
   8 label [label:0x939a9bc]
  10 move [Base:[ecx|L] Disp: 8|J] [ediesi|J] 
  12 move [Base:[ecx|L] Disp: 16|L] [ebx|L] 
  14 null_check [ebx|L]   [bci:9]
  16 move [ebx|L] [ecx|L] 
     move [ediesi|J] [dbl_stack:1|J] 
  18 optvirtual call: [addr: 0x0] [recv: [ecx|L]] [result: [eax|I]] [bci:9]
  22 convert [i2l] [eax|I] [ecxeax|J] 
  24 move [dbl_stack:1|J] [ediesi|J] 
  26 add [ediesi|J] [ecxeax|J] [ediesi|J]
     move [stack:3|L] [ecx|L] 
  28 move [ediesi|J] [Base:[ecx|L] Disp: 8|J] 
  30 move [Base:[ecx|L] Disp: 16|L] [ebx|L] 
  32 null_check [ebx|L]   [bci:26]
  34 move [ebx|L] [ecx|L] 
     move [ediesi|J] [dbl_stack:5|J] 
  36 optvirtual call: [addr: 0x0] [recv: [ecx|L]] [result: [eax|I]] [bci:26]
  40 convert [i2l] [eax|I] [ecxeax|J] 
     move [dbl_stack:5|J] [ediesi|J] 
  44 add [ecxeax|J] [ediesi|J] [ecxeax|J]
     move [stack:3|L] [esi|L] 
  46 move [ecxeax|J] [Base:[esi|L] Disp: 8|J] 
  48 move [Base:[esi|L] Disp: 16|L] [edi|L] 
  50 null_check [edi|L]   [bci:43]
     move [ecxeax|J] [dbl_stack:7|J] 
  52 move [edi|L] [ecx|L] 
  54 optvirtual call: [addr: 0x0] [recv: [ecx|L]] [result: [eax|I]] [bci:43]
  58 convert [i2l] [eax|I] [ecxeax|J] 
     move [dbl_stack:7|J] [ediesi|J] 
  62 add [ecxeax|J] [ediesi|J] [ecxeax|J]
     move [stack:3|L] [esi|L] 
  64 move [ecxeax|J] [Base:[esi|L] Disp: 8|J] 
  66 move [Base:[esi|L] Disp: 16|L] [edi|L] 
  68 null_check [edi|L]   [bci:60]
     move [ecxeax|J] [dbl_stack:9|J] 
  70 move [edi|L] [ecx|L] 
  72 optvirtual call: [addr: 0x0] [recv: [ecx|L]] [result: [eax|I]] [bci:60]
  76 convert [i2l] [eax|I] [eaxesi|J] 
     move [dbl_stack:9|J] [ecxedi|J] 
  80 add [eaxesi|J] [ecxedi|J] [eaxesi|J]
     move [stack:3|L] [ecx|L] 
  82 move [eaxesi|J] [Base:[ecx|L] Disp: 8|J] 
  84 return   

c2-result.txt

C2
looks like next name.hashCode's name is loaded before storing previous result.


jdk1.7.0-b147/fastdebug/bin/java -XX:CompileOnly=gvnex::doHashSum -XX:+PrintOptoAssembly gvnex
VM option 'CompileOnly=gvnex::doHashSum'
VM option '+PrintOptoAssembly'
CompileOnly: compileonly *gvnex*.doHashSum
{method} 
 - klass: {other class}
 - this oop:          0x91238080
 - method holder:     'gvnex'
 - constants:         0x91237e10 constant pool [38] for 'gvnex' cache=0x912382e0
 - access:            0x81000000  
 - name:              'doHashSum'
 - signature:         '()V'
 - max stack:         5
 - max locals:        1
 - size of params:    1
 - method size:       24
 - vtable index:      5
 - i2i entry:         0xb4759e20
 - adapter:           0x09d8b6cc
 - compiled entry     0xb47f8ee8
 - code size:         69
 - code start:        0x91238030
 - code end (excl):   0x91238075
 - method data:       0x91238950
 - checked ex length: 0
 - linenumber start:  0x91238075
 - localvar length:   0
#
#  void ( gvnex:NotNull * )
#
#r000 ecx   : parm 0: gvnex:NotNull *
# -- Old esp -- Framesize: 48 --
#r045 esp+44: return address
#r044 esp+40: pad2, in_preserve
#r043 esp+36: pad2, in_preserve
#r042 esp+32: Fixed slot 0
#r053 esp+28: spill
#r052 esp+24: spill
#r051 esp+20: spill
#r050 esp+16: spill
#r049 esp+12: spill
#r048 esp+ 8: spill
#r047 esp+ 4: spill
#r046 esp+ 0: spill
#
000   N201: #	B1 <- BLOCK HEAD IS JUNK   Freq: 1
000   	CMP    EAX,[ECX+4]	# Inline cache check
	JNE    SharedRuntime::handle_ic_miss_stub
	NOP
	NOP
	NOP

000
00c   B1: #	B10 B2 <- BLOCK HEAD IS JUNK   Freq: 1
00c   	# stack bang
	PUSHL  EBP
	SUB    ESP,40	# Create frame
01a   	MOV    EBP,ECX
01c   	MOV    ECX,[ECX + #16] ! Field gvnex.name
01f   	TEST   ECX,ECX
021   	Je    B10  P=0.000001 C=-1.000000
021
027   B2: #	B14 B3 <- B1  Freq: 0.999999
027   	MOV    ESI,EBP
029   	MOV    EAX.lo,[ESI + #8]	# long
	MOV    EAX.hi,[ESI + #8]+4 ! Field gvnex.sum
02f   	MOV    [ESP + #16],EAX
	MOV    [ESP + #20],EDX
037   	CALL,static  java.lang.String::hashCode
        # gvnex::doHashSum @ bci:9  L[0]=EBP STK[0]=EBP STK[1]=esp + #16 STK[2]=_
        # OopMap{ebp=Oop off=60}
03c
03c   B3: #	B11 B4 <- B2  Freq: 0.999979
        # Block is sole successor of call
03c   	MOV    ECX,[EBP + #16] ! Field gvnex.name
03f   	MOV    EAX.lo,EAX
	MOV    EAX.hi,EAX
	SAR    EAX.hi,31
044   	ADD    EAX.lo,[ESP + #16]
	ADC    EAX.hi,[ESP + #16]+4
04c   	MOV    [ESP + #8],EAX
	MOV    [ESP + #12],EDX
054   	MOV    [EBP + #8],EAX.lo
	MOV    [EBP + #8]+4,EAX.hi ! Field gvnex.sum
05a   	TEST   ECX,ECX
05c   	Je    B11  P=0.000001 C=-1.000000
05c
062   B4: #	B15 B5 <- B3  Freq: 0.999978
062   	NOP 	# 1 bytes pad for loops and calls
063   	CALL,static  java.lang.String::hashCode
        # gvnex::doHashSum @ bci:26  L[0]=EBP STK[0]=EBP STK[1]=esp + #8 STK[2]=_
        # OopMap{ebp=Oop off=104}
068
068   B5: #	B12 B6 <- B4  Freq: 0.999958
        # Block is sole successor of call
068   	MOV    ECX,[EBP + #16] ! Field gvnex.name
06b   	MOV    EAX.lo,EAX
	MOV    EAX.hi,EAX
	SAR    EAX.hi,31
070   	ADD    EAX.lo,[ESP + #8]
	ADC    EAX.hi,[ESP + #8]+4
078   	MOV    [ESP + #8],EAX
	MOV    [ESP + #12],EDX
080   	MOV    [EBP + #8],EAX.lo
	MOV    [EBP + #8]+4,EAX.hi ! Field gvnex.sum
086   	TEST   ECX,ECX
088   	Je,s  B12  P=0.000001 C=-1.000000
088
08a   B6: #	B16 B7 <- B5  Freq: 0.999957
08a   	NOP 	# 1 bytes pad for loops and calls
08b   	CALL,static  java.lang.String::hashCode
        # gvnex::doHashSum @ bci:43  L[0]=EBP STK[0]=EBP STK[1]=esp + #8 STK[2]=_
        # OopMap{ebp=Oop off=144}
090
090   B7: #	B13 B8 <- B6  Freq: 0.999937
        # Block is sole successor of call
090   	MOV    ECX,[EBP + #16] ! Field gvnex.name
093   	MOV    EAX.lo,EAX
	MOV    EAX.hi,EAX
	SAR    EAX.hi,31
098   	ADD    EAX.lo,[ESP + #8]
	ADC    EAX.hi,[ESP + #8]+4
0a0   	MOV    [ESP + #0],EAX
	MOV    [ESP + #4],EDX
0a7   	MOV    [EBP + #8],EAX.lo
	MOV    [EBP + #8]+4,EAX.hi ! Field gvnex.sum
0ad   	TEST   ECX,ECX
0af   	Je,s  B13  P=0.000001 C=-1.000000
0af
0b1   B8: #	B17 B9 <- B7  Freq: 0.999936
0b1   	NOP 	# 2 bytes pad for loops and calls
0b3   	CALL,static  java.lang.String::hashCode
        # gvnex::doHashSum @ bci:60  L[0]=_ STK[0]=EBP STK[1]=esp + #0 STK[2]=_
        # OopMap{ebp=Oop off=184}
0b8
0b8   B9: #	N201 <- B8  Freq: 0.999916
        # Block is sole successor of call
0b8   	MOV    ECX.lo,EAX
	MOV    ECX.hi,EAX
	SAR    ECX.hi,31
0bf   	ADD    ECX.lo,[ESP + #0]
	ADC    ECX.hi,[ESP + #0]+4
0c6   	MOV    [EBP + #8],ECX.lo
	MOV    [EBP + #8]+4,ECX.hi ! Field gvnex.sum
0cc   	ADD    ESP,40	# Destroy frame
	POPL   EBP
	TEST   PollPage,EAX	! Poll Safepoint
	
0d6   	RET
0d6
0d7   B10: #	N201 <- B1  Freq: 1.01328e-06
0d7   	MOV    ECX,#-10
0dc   	NOP 	# 3 bytes pad for loops and calls
0df   	CALL,static  wrapper for: uncommon_trap(reason='null_check' action='maybe_recompile')
        # gvnex::doHashSum @ bci:9  L[0]=_ STK[0]=_ STK[1]=_ STK[2]=_ STK[3]=#NULL
        # OopMap{off=228}
0e4   	INT3   ; ShouldNotReachHere
0e4
0e9   B11: #	N201 <- B3  Freq: 1.01326e-06
0e9   	MOV    ECX,#-10
0ee   	NOP 	# 1 bytes pad for loops and calls
0ef   	CALL,static  wrapper for: uncommon_trap(reason='null_check' action='maybe_recompile')
        # gvnex::doHashSum @ bci:26  L[0]=_ STK[0]=_ STK[1]=_ STK[2]=_ STK[3]=#NULL
        # OopMap{off=244}
0f4   	INT3   ; ShouldNotReachHere
0f4
0f9   B12: #	N201 <- B5  Freq: 1.01324e-06
0f9   	MOV    ECX,#-10
0fe   	NOP 	# 1 bytes pad for loops and calls
0ff   	CALL,static  wrapper for: uncommon_trap(reason='null_check' action='maybe_recompile')
        # gvnex::doHashSum @ bci:43  L[0]=_ STK[0]=_ STK[1]=_ STK[2]=_ STK[3]=#NULL
        # OopMap{off=260}
104   	INT3   ; ShouldNotReachHere
104
109   B13: #	N201 <- B7  Freq: 1.01321e-06
109   	MOV    ECX,#-10
10e   	NOP 	# 1 bytes pad for loops and calls
10f   	CALL,static  wrapper for: uncommon_trap(reason='null_check' action='maybe_recompile')
        # gvnex::doHashSum @ bci:60  L[0]=_ STK[0]=_ STK[1]=_ STK[2]=_ STK[3]=#NULL
        # OopMap{off=276}
114   	INT3   ; ShouldNotReachHere
114
119   B14: #	B18 <- B2  Freq: 9.99999e-06
119   	# exception oop is in EAX; no code emitted
119   	MOV    ECX,EAX
11b   	JMP,s  B18
11b
11d   B15: #	B18 <- B4  Freq: 9.99978e-06
11d   	# exception oop is in EAX; no code emitted
11d   	MOV    ECX,EAX
11f   	JMP,s  B18
11f
121   B16: #	B18 <- B6  Freq: 9.99957e-06
121   	# exception oop is in EAX; no code emitted
121   	MOV    ECX,EAX
123   	JMP,s  B18
123
125   B17: #	B18 <- B8  Freq: 9.99936e-06
125   	# exception oop is in EAX; no code emitted
125   	MOV    ECX,EAX
125
127   B18: #	N201 <- B14 B15 B16 B17  Freq: 3.99987e-05
127   	ADD    ESP,40	# Destroy frame
	POPL   EBP
	
12b   	JMP    rethrow_stub
12b

gvnex.java

public class gvnex {
  String name;
  public static void main(String[] args) {
    gvnex ge = new gvnex("john");
    for (int i = 0; i < 1000000; i++) {
      ge.doHashSum();
    } 
  }
  void doHashSum() {
    sum += name.hashCode();
    sum += name.hashCode();
    sum += name.hashCode();
    sum += name.hashCode();
  }
  public gvnex(String name) { this.name = name; }
  long sum = 0L;
}