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llvm-project/llvm/test/Transforms/GVN/pre-load.ll

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Change tests from "opt %s" to "opt < %s" so that opt doesn't see the input filename so that opt doesn't print the input filename in the output so that grep lines in the tests don't unintentionally match strings in the input filename. llvm-svn: 81537
2009-09-12 02:01:28 +08:00
; RUN: opt < %s -gvn -enable-load-pre -S | grep {%PRE = phi}
Implement PRE of loads in the GVN pass with a pretty cheap and straight-forward implementation. This does not require any extra alias analysis queries beyond what we already do for non-local loads. Some programs really really like load PRE. For example, SPASS triggers this ~1000 times, ~300 times in 255.vortex, and ~1500 times on 403.gcc. The biggest limitation to the implementation is that it does not split critical edges. This is a huge killer on many programs and should be addressed after the initial patch is enabled by default. The implementation of this should incidentally speed up rejection of non-local loads because it avoids creating the repl densemap in cases when it won't be used for fully redundant loads. This is currently disabled by default. Before I turn this on, I need to fix a couple of miscompilations in the testsuite, look at compile time performance numbers, and look at perf impact. This is pretty close to ready though. llvm-svn: 60408
2008-12-02 16:16:11 +08:00
define i32 @test(i32* %p, i1 %C) {
block1:
br i1 %C, label %block2, label %block3
block2:
br label %block4
block3:
%b = bitcast i32 0 to i32
store i32 %b, i32* %p
br label %block4
block4:
%PRE = load i32* %p
ret i32 %PRE
}