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Move PR4517 to README.txt.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75098 91177308-0d34-0410-b5e6-96231b3b80d8
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Nick Lewycky 2009-07-09 04:03:30 +00:00
parent ffd1326ff8
commit f16120475e
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lib/Target/README.txt
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@ -1676,4 +1676,26 @@ entry:
Instcombine should be able to optimize away the loads (and thus the globals).
//===---------------------------------------------------------------------===//
I saw this constant expression in real code after llvm-g++ -O2:
declare extern_weak i32 @0(i64)
define void @foo() {
br i1 icmp eq (i32 zext (i1 icmp ne (i32 (i64)* @0, i32 (i64)* null) to i32),
i32 0), label %cond_true, label %cond_false
cond_true:
ret void
cond_false:
ret void
}
That branch expression should be reduced to:
i1 icmp eq (i32 (i64)* @0, i32 (i64)* null)
It's probably not a perf issue, I just happened to see it while examining
something else and didn't want to forget about it.
//===---------------------------------------------------------------------===//