Extended Description

test: Transforms/InstSimplify/ConstProp/icmp-null.ll
The transformation below is only correct if the gep is over i8*, and not with non-byte-sized types. This is correct: https://alive2.llvm.org/ce/z/S_TsHW

@​g2 = global 4 bytes, align 4
@​g = global 8 bytes, align 4

define i1 @​null_gep_ne_global() {
%__constexpr_0 = ptrtoint * @​g2 to i64
%gep = gep * null, 8 x i64 %__constexpr_0 ; <-- notice the 8 x
%cmp = icmp ne * %gep, @​g
ret i1 %cmp
}
=>
@​g2 = global 4 bytes, align 4
@​g = global 8 bytes, align 4

define i1 @​null_gep_ne_global() {
ret i1 1
}
Transformation doesn't verify!

ERROR: Value mismatch

Example:

Source:
i64 %__constexpr_0 = #x924925b6db6f5564 (10540997870133138788, -7905746203576412828)

• %gep = pointer(non-local, block_id=0, offset=-7905737407482647776)
  i1 %cmp = #x0 (0)

SOURCE MEMORY STATE

NON-LOCAL BLOCKS:
Block 0 > size: 0 align: 1 alloc type: 0 address: 0
Block 1 > size: 4 align: 4 alloc type: 0 address: 10540997870133138788
Block 2 > size: 8 align: 4 alloc type: 0 address: 10541006666226903840

Target:
Source value: #x0 (0)
Target value: #x1 (1)