`OpEmitter::assert_unsigned_int32` blows up for `u32` case if values have high(32nd) bit set

[Denys Zadorozhnyi]

Discovered in #173.

The Rust a >= b (both u32) translates into the following IR:

compiler/tests/integration/expected/ge_u32.hir

Lines 12 to 17 in 663b146

 (block 0 (param v0 i32) (param v1 i32) 
     (let (v3 u32) (cast v0)) 
     (let (v4 u32) (cast v1)) 
     (let (v5 i1) (gte v3 v4)) 
     (let (v6 i32) (cast v5)) 
     (ret v6)) 

From which the following MASM is generated:

compiler/tests/integration/expected/ge_u32.masm

Lines 659 to 670 in 663b146

 dup.0 
 push.2147483648 
 u32and 
 eq.2147483648 
 assertz 
 swap.1 
 dup.0 
 push.2147483648 
 u32and 
 eq.2147483648 
 assertz 
 u32gte 

The assertz fails if a or b have high(32nd) bit set, which is a valid u32 value.

EDIT: Can be reproduced by the commented tests mentioning this issue in their comment.
After the fix, these tests should be enabled.

[Denys Zadorozhnyi]

@bitwalker I hit it in #225. As a temporary workaround, I suggest we disable it and emit nothing when casting to u32.

[Paul Schoenfelder]

Just to confirm a detail here: the bit being set is the 32nd bit? Or the 31st? 2^32 is not representable as a 32 bit integer, 2^32-1 is the maximum value that will fit in 32 bits.

[Denys Zadorozhnyi]

From the get_inputs test the value under cast is 4294967280 which is a valid u32 value with the 32nd bit set. But we're expecting the 32nd bit to be zero for u32 at

compiler/codegen/masm/src/codegen/emit/int32.rs

Line 86 in 5904494

 self.is_const_flag_set_u32(SIGN_BIT);