It also allows nested { } expressions, as now that they are sized, we can merge pull bits from the nested value.
In the current behaviour, everything in { } must have been convertible to a single bit.
However, now that binary literals are sized, its useful to be able to initialize a range of bits.
So, for example, its now possible to do
bits<8> x = { 0, 1, { 0b1001 }, 0, 0b0 }
llvm-svn: 215086
Instead of these becoming an integer literal internally, they now become bits<n> values.
Prior to this change, 0b001 was 1 bit long. This is confusing as clearly the user gave 3 bits.
This new type holds both the literal value and the size, and so can ensure sizes match on initializers.
For example, this used to be legal
bits<1> x = 0b00;
but now it must be written as
bits<2> x = 0b00;
llvm-svn: 215084
Prior to this change, it was legal to do something like
bits<2> opc = { 0, 1 };
bits<2> opc2 = { 1, 0 };
bits<2> a = { opc, opc2 };
This involved silently dropping bits from opc and opc2 which is very hard to debug.
Now the above test would be an error. Having tested with an assert, none of LLVM/clang was relying on this behaviour.
Thanks to Adam Nemet for the above test.
llvm-svn: 215083
Jean-Luc Duprat