llvm-6502/test/Transforms/GVN/lpre-basic.ll

; RUN: llvm-as < %s | opt -gvn -enable-load-pre | llvm-dis | grep {%PRE = phi}

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
}
Fix test/Transforms/GVN/pre-load.ll git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60594 91177308-0d34-0410-b5e6-96231b3b80d8 2008-12-05 17:04:12 +00:00			`; RUN: llvm-as < %s \| opt -gvn -enable-load-pre \| llvm-dis \| 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. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60408 91177308-0d34-0410-b5e6-96231b3b80d8 2008-12-02 08:16:11 +00:00
			`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`
			`}`