RFR: 8273021: C2: Improve Add and Xor ideal optimizations
Tobias Hartmann
thartmann at openjdk.java.net
Thu Sep 2 14:24:18 UTC 2021
On Thu, 26 Aug 2021 09:19:41 GMT, Yi Yang <yyang at openjdk.org> wrote:
> Greetings. This patch adds the following identical equations for Add and Xor node, respectively, which probably drives further optimizations.
>
>
> ~(x-1) => -x
> ~x + 1 => -x
>
>
>
> Verified by generated opto assembly, maybe an IR verification test can be added later.
>
> ============================= C2-compiled nmethod ==============================
> ----------------------- MetaData before Compile_id = 1 ------------------------
> {method}
> - this oop: 0x00007fe29f003518
> - method holder: 'compiler/c2/TestAddXorIdeal'
> - constants: 0x00007fe29f003248 constant pool [38] {0x00007fe29f003248} for 'compiler/c2/TestAddXorIdeal' cache=0x00007fe29f0038f0
> - access: 0x81000009 public static
> - name: 'test1'
> - signature: '(I)I'
> - max stack: 3
> - max locals: 1
> - size of params: 1
> - method size: 13
> - vtable index: -2
> - i2i entry: 0x00007fe2fd23fc00
> - adapters: AHE at 0x00007fe3082160d0: 0xa i2c: 0x00007fe2fd34c660 c2i: 0x00007fe2fd34c719 c2iUV: 0x00007fe2fd34c6e3 c2iNCI: 0x00007fe2fd34c756
> - compiled entry 0x00007fe2fd34c719
> - code size: 6
> - code start: 0x00007fe29f003508
> - code end (excl): 0x00007fe29f00350e
> - method data: 0x00007fe29f0070f8
> - checked ex length: 0
> - linenumber start: 0x00007fe29f00350e
> - localvar length: 0
>
> ------------------------ OptoAssembly for Compile_id = 1 -----------------------
> #
> # int ( int )
> #
> #r018 rsi : parm 0: int
> # -- Old rsp -- Framesize: 32 --
> #r591 rsp+28: in_preserve
> #r590 rsp+24: return address
> #r589 rsp+20: in_preserve
> #r588 rsp+16: saved fp register
> #r587 rsp+12: pad2, stack alignment
> #r586 rsp+ 8: pad2, stack alignment
> #r585 rsp+ 4: Fixed slot 1
> #r584 rsp+ 0: Fixed slot 0
> #
> 000 N1: # out( B1 ) <- in( B1 ) Freq: 1
>
> 000 B1: # out( N1 ) <- BLOCK HEAD IS JUNK Freq: 1
> 000 # stack bang (96 bytes)
> pushq rbp # Save rbp
> subq rsp, #16 # Create frame
>
> 00c movl RAX, RSI # spill
> 00e negl RAX # int
> 010 addq rsp, 16 # Destroy frame
> popq rbp
> cmpq rsp, poll_offset[r15_thread]
> ja #safepoint_stub # Safepoint: poll for GC
>
> 022 ret
>
> --------------------------------------------------------------------------------
>
> ============================= C2-compiled nmethod ==============================
> ----------------------- MetaData before Compile_id = 3 ------------------------
> {method}
> - this oop: 0x00007fe29f003668
> - method holder: 'compiler/c2/TestAddXorIdeal'
> - constants: 0x00007fe29f003248 constant pool [38] {0x00007fe29f003248} for 'compiler/c2/TestAddXorIdeal' cache=0x00007fe29f0038f0
> - access: 0x81000009 public static
> - name: 'test3'
> - signature: '(J)J'
> - max stack: 5
> - max locals: 2
> - size of params: 2
> - method size: 13
> - vtable index: -2
> - i2i entry: 0x00007fe2fd23fc00
> - adapters: AHE at 0x00007fe30829c8f0: 0xbe i2c: 0x00007fe2fd2d88e0 c2i: 0x00007fe2fd2d89c0 c2iUV: 0x00007fe2fd2d898a c2iNCI: 0x00007fe2fd2d89fd
> - compiled entry 0x00007fe2fd2d89c0
> - code size: 8
> - code start: 0x00007fe29f003658
> - code end (excl): 0x00007fe29f003660
> - method data: 0x00007fe29f007408
> - checked ex length: 0
> - linenumber start: 0x00007fe29f003660
> - localvar length: 0
>
> ------------------------ OptoAssembly for Compile_id = 3 -----------------------
> #
> # long/half ( long, half )
> #
> #r018 rsi:rsi : parm 0: long
> # -- Old rsp -- Framesize: 32 --
> #r591 rsp+28: in_preserve
> #r590 rsp+24: return address
> #r589 rsp+20: in_preserve
> #r588 rsp+16: saved fp register
> #r587 rsp+12: pad2, stack alignment
> #r586 rsp+ 8: pad2, stack alignment
> #r585 rsp+ 4: Fixed slot 1
> #r584 rsp+ 0: Fixed slot 0
> #
> 000 N1: # out( B1 ) <- in( B1 ) Freq: 1
>
> 000 B1: # out( N1 ) <- BLOCK HEAD IS JUNK Freq: 1
> 000 # stack bang (96 bytes)
> pushq rbp # Save rbp
> subq rsp, #16 # Create frame
>
> 00c movq RAX, RSI # spill
> 00f negq RAX # long
> 012 addq rsp, 16 # Destroy frame
> popq rbp
> cmpq rsp, poll_offset[r15_thread]
> ja #safepoint_stub # Safepoint: poll for GC
>
> 024 ret
>
> --------------------------------------------------------------------------------
>
> ============================= C2-compiled nmethod ==============================
> ----------------------- MetaData before Compile_id = 2 ------------------------
> {method}
> - this oop: 0x00007fe29f0035c0
> - method holder: 'compiler/c2/TestAddXorIdeal'
> - constants: 0x00007fe29f003248 constant pool [38] {0x00007fe29f003248} for 'compiler/c2/TestAddXorIdeal' cache=0x00007fe29f0038f0
> - access: 0x81000009 public static
> - name: 'test2'
> - signature: '(I)I'
> - max stack: 3
> - max locals: 1
> - size of params: 1
> - method size: 13
> - vtable index: -2
> - i2i entry: 0x00007fe2fd23fc00
> - adapters: AHE at 0x00007fe3082160d0: 0xa i2c: 0x00007fe2fd34c660 c2i: 0x00007fe2fd34c719 c2iUV: 0x00007fe2fd34c6e3 c2iNCI: 0x00007fe2fd34c756
> - compiled entry 0x00007fe2fd34c719
> - code size: 6
> - code start: 0x00007fe29f0035b0
> - code end (excl): 0x00007fe29f0035b6
> - method data: 0x00007fe29f007280
> - checked ex length: 0
> - linenumber start: 0x00007fe29f0035b6
> - localvar length: 0
>
> ------------------------ OptoAssembly for Compile_id = 2 -----------------------
> #
> # int ( int )
> #
> #r018 rsi : parm 0: int
> # -- Old rsp -- Framesize: 32 --
> #r591 rsp+28: in_preserve
> #r590 rsp+24: return address
> #r589 rsp+20: in_preserve
> #r588 rsp+16: saved fp register
> #r587 rsp+12: pad2, stack alignment
> #r586 rsp+ 8: pad2, stack alignment
> #r585 rsp+ 4: Fixed slot 1
> #r584 rsp+ 0: Fixed slot 0
> #
> 000 N1: # out( B1 ) <- in( B1 ) Freq: 1
>
> 000 B1: # out( N1 ) <- BLOCK HEAD IS JUNK Freq: 1
> 000 # stack bang (96 bytes)
> pushq rbp # Save rbp
> subq rsp, #16 # Create frame
>
> 00c movl RAX, RSI # spill
> 00e negl RAX # int
> 010 addq rsp, 16 # Destroy frame
> popq rbp
> cmpq rsp, poll_offset[r15_thread]
> ja #safepoint_stub # Safepoint: poll for GC
>
> 022 ret
>
> --------------------------------------------------------------------------------
>
> ============================= C2-compiled nmethod ==============================
> ----------------------- MetaData before Compile_id = 4 ------------------------
> {method}
> - this oop: 0x00007fe29f003710
> - method holder: 'compiler/c2/TestAddXorIdeal'
> - constants: 0x00007fe29f003248 constant pool [38] {0x00007fe29f003248} for 'compiler/c2/TestAddXorIdeal' cache=0x00007fe29f0038f0
> - access: 0x81000009 public static
> - name: 'test4'
> - signature: '(J)J'
> - max stack: 5
> - max locals: 2
> - size of params: 2
> - method size: 13
> - vtable index: -2
> - i2i entry: 0x00007fe2fd23fc00
> - adapters: AHE at 0x00007fe30829c8f0: 0xbe i2c: 0x00007fe2fd2d88e0 c2i: 0x00007fe2fd2d89c0 c2iUV: 0x00007fe2fd2d898a c2iNCI: 0x00007fe2fd2d89fd
> - compiled entry 0x00007fe2fd2d89c0
> - code size: 8
> - code start: 0x00007fe29f003700
> - code end (excl): 0x00007fe29f003708
> - method data: 0x00007fe29f0075a0
> - checked ex length: 0
> - linenumber start: 0x00007fe29f003708
> - localvar length: 0
>
> ------------------------ OptoAssembly for Compile_id = 4 -----------------------
> #
> # long/half ( long, half )
> #
> #r018 rsi:rsi : parm 0: long
> # -- Old rsp -- Framesize: 32 --
> #r591 rsp+28: in_preserve
> #r590 rsp+24: return address
> #r589 rsp+20: in_preserve
> #r588 rsp+16: saved fp register
> #r587 rsp+12: pad2, stack alignment
> #r586 rsp+ 8: pad2, stack alignment
> #r585 rsp+ 4: Fixed slot 1
> #r584 rsp+ 0: Fixed slot 0
> #
> 000 N1: # out( B1 ) <- in( B1 ) Freq: 1
>
> 000 B1: # out( N1 ) <- BLOCK HEAD IS JUNK Freq: 1
> 000 # stack bang (96 bytes)
> pushq rbp # Save rbp
> subq rsp, #16 # Create frame
>
> 00c movq RAX, RSI # spill
> 00f negq RAX # long
> 012 addq rsp, 16 # Destroy frame
> popq rbp
> cmpq rsp, poll_offset[r15_thread]
> ja #safepoint_stub # Safepoint: poll for GC
>
> 024 ret
src/hotspot/share/opto/addnode.cpp line 1014:
> 1012: return new SubINode(phase->makecon(TypeInt::ZERO), in1->in(1));
> 1013: }
> 1014: } else if (op2 == Op_AddI && phase->type(in1) == TypeInt::MINUS_1) {
Why do you need to check both inputs for constant -1? Shouldn't `AddNode::Ideal` canonicalize the inputs and ensure that constants are moved to the second input?
https://github.com/openjdk/jdk/blob/599d07c0db9c85e4dae35d1c54a63407d32eaedd/src/hotspot/share/opto/addnode.hpp#L52-L54
test/hotspot/jtreg/compiler/c2/TestAddXorIdeal.java line 30:
> 28: * @summary C2: Improve Add and Xor ideal optimizations
> 29: * @library /test/lib
> 30: * @run main/othervm -XX:-Inline -XX:-TieredCompilation -XX:TieredStopAtLevel=4 -XX:CompileCommand=compileonly,compiler.c2.TestAddXorIdeal::* compiler.c2.TestAddXorIdeal
What about `-XX:CompileCommand=dontinline,compiler.c2.TestAddXorIdeal::test*` Instead of disabling all inlining and limiting compilation?
test/hotspot/jtreg/compiler/c2/TestAddXorIdeal.java line 59:
> 57: Asserts.assertTrue(test2(i - 7) == -(i - 7));
> 58: Asserts.assertTrue(test3(i + 100) == -(i + 100));
> 59: Asserts.assertTrue(test4(i - 1024) == -(i - 1024));
What about using random numbers for better coverage?
-------------
PR: https://git.openjdk.java.net/jdk/pull/5266
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