[PATCH] D32252: [GVN] Add phi-translate for scalarpre as a temporary solution

[Wei Mi via Phabricator via llvm-commits]

wmi created this revision.
Herald added a subscriber: Prazek.

Now phi-translate only exists in loadpre. scalarpre doesn't have phi-translate support, so it will miss some simple pre opportunities. Like the following testcase, current scalarpre cannot recognize the last "a * b" is fully redundent because a and b used by the last "a * b" expr  are both defined by phis.

long a[100], b[100];
long g1, g2, g3;

__attribute__((pure))
long goo();

void foo(long a, long b, long c, long d) {

  g1 = a * b;
  if (__builtin_expect(g2 > 3, 0)) {
    a = c;
    b = d;
    g2 = a * b;
  }
  g3 = a * b;      // fully redundant.

}

The patch adds support for phi-translate in scalarpre. This is only a temporary solution before the newpre based on newgvn is available.


Repository:
  rL LLVM

https://reviews.llvm.org/D32252

Files:
  include/llvm/Transforms/Scalar/GVN.h
  lib/Transforms/Scalar/GVN.cpp
  test/Transforms/GVN/PRE/phi-translate-2.ll
  test/Transforms/GVN/PRE/pre-gep-load.ll
  test/Transforms/GVN/PRE/pre-load.ll

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