From fa2eec9a67a5134065176babcaddf3867fe47920 Mon Sep 17 00:00:00 2001 From: Jeffrey A Law Date: Thu, 28 Jun 2001 18:24:55 +0000 Subject: [PATCH] ssa-dce.c (eliminate_dead_code): Properly handle control dependencies implied by PHI nodes. * ssa-dce.c (eliminate_dead_code): Properly handle control dependencies implied by PHI nodes. From-SVN: r43643 --- gcc/ChangeLog | 3 +++ gcc/ssa-dce.c | 35 +++++++++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index a6f96b4f54e..5d363c36194 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -11,6 +11,9 @@ Thu Jun 28 20:13:11 CEST 2001 Jan Hubicka Thu Jun 28 11:19:42 2001 Jeffrey A Law (law@cygnus.com) + * ssa-dce.c (eliminate_dead_code): Properly handle control + dependencies implied by PHI nodes. + * ssa-dce.c (eliminate_dead_code): Remove fake edges from the CFG after dead code elimination is complete. 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); + } + }); + + } + } } } -- 2.30.2