rust/compiler/rustc_mir_transform
bors 8d76d07666 Auto merge of #116012 - cjgillot:gvn-const, r=oli-obk
Implement constant propagation on top of MIR SSA analysis

This implements the idea I proposed in https://github.com/rust-lang/rust/pull/110719#issuecomment-1718324700

Based on https://github.com/rust-lang/rust/pull/109597

The value numbering "GVN" pass formulates each rvalue that appears in MIR with an abstract form (the `Value` enum), and assigns an integer `VnIndex` to each. This abstract form can be used to deduplicate values, reusing an earlier local that holds the same value instead of recomputing. This part is proposed in #109597.

From this abstract representation, we can perform more involved simplifications, for example in https://github.com/rust-lang/rust/pull/111344.

With the abstract representation `Value`, we can also attempt to evaluate each to a constant using the interpreter. This builds a `VnIndex -> OpTy` map. From this map, we can opportunistically replace an operand or a rvalue with a constant if their value has an associated `OpTy`.

The most relevant commit is [Evaluated computed values to constants.](2767c4912e)"

r? `@oli-obk`
2023-12-30 03:45:58 +00:00
..
src Auto merge of #116012 - cjgillot:gvn-const, r=oli-obk 2023-12-30 03:45:58 +00:00
Cargo.toml coverage: Avoid unnecessary macros in unit tests 2023-12-07 11:12:48 +11:00
messages.ftl Print list of missing target features when calling a function with target features outside an unsafe block 2023-11-27 19:13:11 +01:00