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author | Aaron Patterson <tenderlove@ruby-lang.org> | 2022-11-15 11:46:18 -0800 |
---|---|---|
committer | Aaron Patterson <aaron.patterson@gmail.com> | 2022-11-18 12:04:10 -0800 |
commit | 9e067df76bda7384e8f3ddda2b348f3a742eb784 (patch) | |
tree | c231960ee347399930d6aa304b148d208a372611 /yjit/src/asm | |
parent | 6582f34831cc665b2adcf7d475aceb9b918badb6 (diff) | |
download | ruby-9e067df76bda7384e8f3ddda2b348f3a742eb784.tar.gz |
32 bit comparison on shape id
This commit changes the shape id comparisons to use a 32 bit comparison
rather than 64 bit. That means we don't need to load the shape id to a
register on x86 machines.
Given the following program:
```ruby
class Foo
def initialize
@foo = 1
@bar = 1
end
def read
[@foo, @bar]
end
end
foo = Foo.new
foo.read
foo.read
foo.read
foo.read
foo.read
puts RubyVM::YJIT.disasm(Foo.instance_method(:read))
```
The machine code we generated _before_ this change is like this:
```
== BLOCK 1/4, ISEQ RANGE [0,3), 65 bytes ======================
# getinstancevariable
0x559a18623023: mov rax, qword ptr [r13 + 0x18]
# guard object is heap
0x559a18623027: test al, 7
0x559a1862302a: jne 0x559a1862502d
0x559a18623030: cmp rax, 4
0x559a18623034: jbe 0x559a1862502d
# guard shape, embedded, and T_OBJECT
0x559a1862303a: mov rcx, qword ptr [rax]
0x559a1862303d: movabs r11, 0xffff00000000201f
0x559a18623047: and rcx, r11
0x559a1862304a: movabs r11, 0xb000000002001
0x559a18623054: cmp rcx, r11
0x559a18623057: jne 0x559a18625046
0x559a1862305d: mov rax, qword ptr [rax + 0x18]
0x559a18623061: mov qword ptr [rbx], rax
== BLOCK 2/4, ISEQ RANGE [3,6), 0 bytes =======================
== BLOCK 3/4, ISEQ RANGE [3,6), 47 bytes ======================
# gen_direct_jmp: fallthrough
# getinstancevariable
# regenerate_branch
# getinstancevariable
# regenerate_branch
0x559a18623064: mov rax, qword ptr [r13 + 0x18]
# guard shape, embedded, and T_OBJECT
0x559a18623068: mov rcx, qword ptr [rax]
0x559a1862306b: movabs r11, 0xffff00000000201f
0x559a18623075: and rcx, r11
0x559a18623078: movabs r11, 0xb000000002001
0x559a18623082: cmp rcx, r11
0x559a18623085: jne 0x559a18625099
0x559a1862308b: mov rax, qword ptr [rax + 0x20]
0x559a1862308f: mov qword ptr [rbx + 8], rax
```
After this change, it's like this:
```
== BLOCK 1/4, ISEQ RANGE [0,3), 41 bytes ======================
# getinstancevariable
0x5560c986d023: mov rax, qword ptr [r13 + 0x18]
# guard object is heap
0x5560c986d027: test al, 7
0x5560c986d02a: jne 0x5560c986f02d
0x5560c986d030: cmp rax, 4
0x5560c986d034: jbe 0x5560c986f02d
# guard shape
0x5560c986d03a: cmp word ptr [rax + 6], 0x19
0x5560c986d03f: jne 0x5560c986f046
0x5560c986d045: mov rax, qword ptr [rax + 0x10]
0x5560c986d049: mov qword ptr [rbx], rax
== BLOCK 2/4, ISEQ RANGE [3,6), 0 bytes =======================
== BLOCK 3/4, ISEQ RANGE [3,6), 23 bytes ======================
# gen_direct_jmp: fallthrough
# getinstancevariable
# regenerate_branch
# getinstancevariable
# regenerate_branch
0x5560c986d04c: mov rax, qword ptr [r13 + 0x18]
# guard shape
0x5560c986d050: cmp word ptr [rax + 6], 0x19
0x5560c986d055: jne 0x5560c986f099
0x5560c986d05b: mov rax, qword ptr [rax + 0x18]
0x5560c986d05f: mov qword ptr [rbx + 8], rax
```
The first ivar read is a bit more complex, but the second ivar read is
much simpler. I think eventually we could teach the context about the
shape, then emit only one shape guard.
Diffstat (limited to 'yjit/src/asm')
-rw-r--r-- | yjit/src/asm/arm64/mod.rs | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/yjit/src/asm/arm64/mod.rs b/yjit/src/asm/arm64/mod.rs index 683711259e..d463613943 100644 --- a/yjit/src/asm/arm64/mod.rs +++ b/yjit/src/asm/arm64/mod.rs @@ -540,8 +540,6 @@ pub fn ldur(cb: &mut CodeBlock, rt: A64Opnd, rn: A64Opnd) { pub fn ldurh(cb: &mut CodeBlock, rt: A64Opnd, rn: A64Opnd) { let bytes: [u8; 4] = match (rt, rn) { (A64Opnd::Reg(rt), A64Opnd::Mem(rn)) => { - assert!(rt.num_bits == 32, "Rt should be a 32 bit register"); - assert!(rn.num_bits == 64, "Rn should be a 64 bit register"); assert!(mem_disp_fits_bits(rn.disp), "Expected displacement to be 9 bits or less"); LoadStore::ldurh(rt.reg_no, rn.base_reg_no, rn.disp as i16).into() |