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45b7e0e48d
The motivating example is:
extern int patatino;
int goo() {
int x = 0;
for (int i = 0; i < 1000000; ++i) {
x *= patatino;
}
return x;
}
Currently SCCP will not realize that this function returns always zero,
therefore will try to unroll and vectorize the loop at -O3 producing an
awful lot of (useless) code. With this change, it will just produce:
0000000000000000 <g>:
xor %eax,%eax
retq
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@289175 91177308-0d34-0410-b5e6-96231b3b80d8
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