This patch adds support for constant propagation of individual structure members through Phi nodes. Each member is handled independently, allowing optimization opportunities when specific members become constant. Also, update the testcase since we are able to optimize the call parameter now.
Copying ValueLatticeElement becomes expensive after https://github.com/llvm/llvm-project/pull/111544. This patch eliminates some redundant copies to improve performance. The code change has been carefully reviewed to ensure that there is no dangling reference. Compile-time improvement: https://llvm-compile-time-tracker.com/compare.php?from=f4359301c033694d36865c7560714164d2050240&to=4ea449bd53feef43403c35d8b815ddca752dbc17&stat=instructions%3Au
This patch implements the todo discussed in https://github.com/llvm/llvm-project/pull/158495#discussion_r2349609838. It also fixes a regression introduced by https://github.com/llvm/llvm-project/pull/161000. See also https://github.com/dtcxzyw/llvm-opt-benchmark/pull/2890#discussion_r2404016316. IR diff: https://github.com/dtcxzyw/llvm-opt-benchmark/pull/2892
If we know x in R1, the range check `x in R2` can be relaxed into `x in Union(R2, Inverse(R1))`. The latter one may be more efficient if we can represent it with one icmp. Fixes regressions introduced by https://github.com/llvm/llvm-project/pull/156497. Proof for `(X & -Pow2) == C -> (X - C) < Pow2`: https://alive2.llvm.org/ce/z/HMgkuu Compile-time impact: https://llvm-compile-time-tracker.com/compare.php?from=ead4f3e271fdf6918aef2ede3a7134811147d276&to=bee3d902dd505cf9b11499ba4f230e4e8ae96b92&stat=instructions%3Au
proof: https://alive2.llvm.org/ce/z/_7PVxq
PredicateInfo needs some no-op to which the predicate can be attached.
Currently this is an ssa.copy intrinsic. This PR replaces it with a
no-op bitcast.
Using a bitcast is more efficient because we don't have the overhead of
an overloaded intrinsic. It also makes things slightly simpler overall.
If the difference between [us]cmp's operands is not greater than 1, we can simplify it into `X - Y`. Alive2: https://alive2.llvm.org/ce/z/JS55so llvm-opt-benchmark diff: https://github.com/dtcxzyw/llvm-opt-benchmark/pull/2464/files
SCCP currently stores instructions whose lattice value has changed in a worklist, and then updates their users in the main loop. This may result in instructions unnecessarily being visited multiple times (as an instruction will often use multiple other instructions). Additionally, we'd often redundantly visit instructions that were already visited when the containing block first became executable. Instead, change the worklist to directly store the instructions that need to be revisited. Additionally, do not add instructions to the worklist that will already be covered by the main basic block walk. This change is conceptually NFC, but is expected to produce minor differences in practice, because the visitation order interacts with the range widening limit.
Currently predicates are allocated on the heap and tracked with an intrusive list. Use a bump pointer allocator instead, which is more efficient. The list is no longer needed, as we don't have to track predicates for freeing. The bump pointer allocator is provided as a parameter for PredicateInfo to allow reusing the same allocator for all functions during IPSCCP.