diff options
Diffstat (limited to 'gcc/ssa-dce.c')
| -rw-r--r-- | gcc/ssa-dce.c | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/gcc/ssa-dce.c b/gcc/ssa-dce.c index 1629803b8e8..4ccd9e01ccb 100644 --- a/gcc/ssa-dce.c +++ b/gcc/ssa-dce.c @@ -558,6 +558,41 @@ eliminate_dead_code () &propagate_necessity_through_operand, (PTR) &unprocessed_instructions); + /* PHI nodes are somewhat special in that each PHI alternative + has data and control dependencies. The data dependencies + are handled via propagate_necessity_through_operand. We + handle the control dependency here. + + We consider the control dependent edges leading to the + predecessor block associated with each PHI alternative + as necessary. */ + if (PHI_NODE_P (current_instruction)) + { + rtvec phi_vec = XVEC (SET_SRC (PATTERN (current_instruction)), 0); + int num_elem = GET_NUM_ELEM (phi_vec); + int v; + + for (v = num_elem - 2; v >= 0; v -= 2) + { + basic_block bb; + + bb = BASIC_BLOCK (INTVAL (RTVEC_ELT (phi_vec, v + 1))); + EXECUTE_IF_CONTROL_DEPENDENT + (cdbte, bb->end, edge_number, + { + rtx jump_insn; + + jump_insn = (INDEX_EDGE_PRED_BB (el, edge_number))->end; + if (((GET_CODE (jump_insn) == JUMP_INSN)) + && UNNECESSARY_P (jump_insn)) + { + RESURRECT_INSN (jump_insn); + VARRAY_PUSH_RTX (unprocessed_instructions, jump_insn); + } + }); + + } + } } } |