Yet to be written.
+ADCE aggressively tries to eliminate code. This pass is similar to + DCE but it assumes that values are dead until proven + otherwise. This is similar to SCCP, except applied to + the liveness of values.
Yet to be written.
+This pass implements a very simple profile guided basic block placement + algorithm. The idea is to put frequently executed blocks together at the + start of the function, and hopefully increase the number of fall-through + conditional branches. If there is no profile information for a particular + function, this pass basically orders blocks in depth-first order.
+The algorithm implemented here is basically "Algo1" from "Profile Guided + Code Positioning" by Pettis and Hansen, except that it uses basic block + counts instead of edge counts. This could be improved in many ways, but is + very simple for now.
+Basically we "place" the entry block, then loop over all successors in a + DFO, placing the most frequently executed successor until we run out of + blocks. Did we mention that this was extremely simplistic? This is + also much slower than it could be. When it becomes important, this pass + will be rewritten to use a better algorithm, and then we can worry about + efficiency.
Yet to be written.
+Correlated Expression Elimination propagates information from conditional + branches to blocks dominated by destinations of the branch. It propagates + information from the condition check itself into the body of the branch, + allowing transformations like these for example: +
+ if (i == 7) + ... 4*i; // constant propagation + + M = i+1; N = j+1; + if (i == j) + X = M-N; // = M-M == 0; ++ +
This is called Correlated Expression Elimination because we eliminate or + simplify expressions that are correlated with the direction of a branch. In + this way we use static information to give us some information about the + dynamic value of a variable.
Yet to be written.
+This pass propagates information about conditional expressions through the + program, allowing it to eliminate conditional branches in some cases.
Yet to be written.
+This file implements constant propagation and merging. It looks for + instructions involving only constant operands and replaces them with a + constant value instead of an instruction. For example: +
add i32 1, 2
i32 3+
NOTE: this pass has a habit of making definitions be dead. It is a good + idea to to run a DIE (Dead Instruction Elimination) pass + sometime after running this pass.