Codegen backend handles compare binops for the unit type

rust/src/librustc_codegen_ssa/mir/rvalue.rs

Lines 586 to 592 in c43d03a

    
           mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt | 
        
           mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => if is_unit { 
        
               bx.cx().const_bool(match op { 
        
                   mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt => false, 
        
                   mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => true, 
        
                   _ => unreachable!() 
        
               })

libcore however doesn't use those for the implementations for PartialEq and PartialOrd for the unit type.

rust/src/libcore/cmp.rs

Lines 933 to 939 in c43d03a

    
           #[stable(feature = "rust1", since = "1.0.0")] 
        
           impl PartialEq for () { 
        
               #[inline] 
        
               fn eq(&self, _other: &()) -> bool { true } 
        
               #[inline] 
        
               fn ne(&self, _other: &()) -> bool { false } 
        
           }

rust/src/libcore/cmp.rs

Lines 980 to 985 in c43d03a

    
           impl PartialOrd for () { 
        
               #[inline] 
        
               fn partial_cmp(&self, _: &()) -> Option<Ordering> { 
        
                   Some(Equal) 
        
               } 
        
           }

This means that the special case in cg_ssa can be removed.

@bjorn3

Hi @bjorn3 @Centril, I'd like to work on this. Would be a good initial contribution to Rust :)

I'm really new to the code base, though. Could you clarify what the cg_ssa means above?

Could you clarify what the cg_ssa means above?

That's librustc_codegen_ssa, a part of the code generation code in rustc. The code in the first snippet is located there.

Thanks for clarifying that! I'll go through the code and post any questions here.

@bjorn3

Would love to help but don't know where to start. If mentoring is still possible please ping me or send me in the right direction somehow 👍 . @bjorn3 @Centril

@jonas-schievink

or maybe @jonas-schievink if your up to the task :)

@luigisHat

@luigisHat I think you just need to look at src/librustc_codegen_ssa/mir/rvalue.rs and remove the check for is_unit that was mentioned. You can check https://rust-lang.github.io/rustc-guide/ for an overview of the compiler and instruction on how to build it and run tests.

@jonas-schievink

@jonas-schievink Thanks seems to be a little simpler then I thought once I dug into the docs. Will do hope your having a good one 👍 .

Auto merge of #63906 - luigishat:cmp_fix, r=bjorn3

Rollup merge of rust-lang#65605 - bjorn3:fix_63906, r=eddyb

Navigation Menu

Repository navigation

Codegen backend handles compare binops for the unit type #63551

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

	mir::BinOp::Ne \| mir::BinOp::Lt \| mir::BinOp::Gt \|
	mir::BinOp::Eq \| mir::BinOp::Le \| mir::BinOp::Ge => if is_unit {
	bx.cx().const_bool(match op {
	mir::BinOp::Ne \| mir::BinOp::Lt \| mir::BinOp::Gt => false,
	mir::BinOp::Eq \| mir::BinOp::Le \| mir::BinOp::Ge => true,
	_ => unreachable!()
	})

	#[stable(feature = "rust1", since = "1.0.0")]
	impl PartialEq for () {
	#[inline]
	fn eq(&self, _other: &()) -> bool { true }
	#[inline]
	fn ne(&self, _other: &()) -> bool { false }
	}

	impl PartialOrd for () {
	#[inline]
	fn partial_cmp(&self, _: &()) -> Option<Ordering> {
	Some(Equal)
	}
	}

Codegen backend handles compare binops for the unit type #63551

Description

Activity

punitkoura commented on Aug 14, 2019

punitkoura commented on Aug 14, 2019

jonas-schievink commented on Aug 14, 2019

punitkoura commented on Aug 15, 2019

TheOregonTrail commented on Aug 25, 2019

TheOregonTrail commented on Aug 25, 2019

jonas-schievink commented on Aug 25, 2019

TheOregonTrail commented on Aug 25, 2019

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions