Am 21.08.24 um 11:31 schrieb Richard Biener:
On Wed, Aug 21, 2024 at 11:19 AM Georg-Johann Lay <a...@gjlay.de> wrote:Hi, in an RTL optimization pass I would like to perform a transformation like from old code: [bb 1] if (condA) ;; insn1 goto label_1; [bb 2] if (cond_B) ;; insn2 goto label_2; to new code: [bb 1] if (cond1) ;; branch1 goto label_2; [bb 2] if (cond2) ;; branch 2 goto label_1; but I am having trouble finding the correct code to accomplish the transformation. Notice that the goto targets have been swapped. The current code WIP looks something like below, where insn1 and insn2 are the old conditional branches: rtx_jump_insn *branch1 = emit_jump_insn_after (cond1, insn1); rtx_jump_insn *branch2 = emit_jump_insn_after (cond2, insn2); JUMP_LABEL (branch1) = label_2; JUMP_LABEL (branch2) = label_1; ++LABEL_NUSES (label_2); ++LABEL_NUSES (label_1); delete_insn (insn1); delete_insn (insn2); Then, in a later pass, some code and label that are not dead are removed. Trying to maintain the new edges by hand, like in delete_insn_and_edges (insn1); delete_insn_and_edges (insn2); make_edge (bb 1, bb (label_2)); make_edge (bb 2, bb (label_1)); runs into ICE in verify_flow_info. Maybe someone can explain how to do it properly or where I can find examples (internals don't help much, and I couldn't find examples in the sources).You want to look at cfghooks.{h,cc} and try to express the transform in terms of that API, likely redirect_edge_and_branch[_force] on both branch edges - that should adjust the jump insn as well (just the target of course, not the comparison).
Thanks, that's what I am looking for. Is there some means to get the edge associated to a branch? Currently I an just using find_edge() with the respective BBs. Johann the current bb
