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Date: Thu, 29 Mar 2012 10:02:00 -0000
Message-ID: <CAHFci2_d_vcB_-iag7p6MeCOjKL60YrAreAbz6AWgY8+=3rCQg@mail.gmail.com>
Subject: Missed optimization in PRE?
From: "Bin.Cheng" <amker.cheng@gmail.com>
To: gcc@gcc.gnu.org
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Hi,
Following is the tree dump of 094t.pre for a test program.
Question is loads of D.5375_12/D.5375_14 are redundant on path <bb2,
bb7, bb5, bb6>,
but why not lowered into basic block 3, where it is used.

BTW, seems no tree pass handles this case currently.

Any idea? Thanks

  int z$imag;
  int z$real;
  int D.5378;
  int D.5377;
  int D.5376;
  int D.5375;

<bb 2>:
  D.5375_11 = REALPART_EXPR <g2>;
  D.5376_12 = IMAGPART_EXPR <g2>;
  D.5377_13 = REALPART_EXPR <g3>;
  D.5378_14 = IMAGPART_EXPR <g3>;
  if (D.5375_11 == D.5377_13)
    goto <bb 3>;
  else
    goto <bb 7>;

<bb 3>:
  if (D.5376_12 == D.5378_14)
    goto <bb 4>;
  else
    goto <bb 7>;

<bb 4>:
  z$real_15 = REALPART_EXPR <g1>;
  z$imag_16 = IMAGPART_EXPR <g1>;
  goto <bb 6>;

<bb 7>:

<bb 5>:
  z$real_17 = REALPART_EXPR <g4>;
  z$imag_18 = IMAGPART_EXPR <g4>;

<bb 6>:
  # z$real_19 = PHI <z$real_15(4), z$real_17(5)>
  # z$imag_20 = PHI <z$imag_16(4), z$imag_18(5)>
  REALPART_EXPR <g1> = z$real_19;
  IMAGPART_EXPR <g1> = z$imag_20;
  return 0;

-- 
Best Regards.