Chris Lattner 7d3c4712e9 When loop rotation happens, it is *very* common for the duplicated condbr ... to be foldable into an uncond branch. When this happens, we can make a much simpler CFG for the loop, which is important for nested loop cases where we want the outer loop to be aggressively optimized. Handle this case more aggressively. For example, previously on phi-duplicate.ll we would get this: define void @test(i32 %N, double* %G) nounwind ssp { entry: %cmp1 = icmp slt i64 1, 1000 br i1 %cmp1, label %bb.nph, label %for.end bb.nph: ; preds = %entry br label %for.body for.body: ; preds = %bb.nph, %for.cond %j.02 = phi i64 [ 1, %bb.nph ], [ %inc, %for.cond ] %arrayidx = getelementptr inbounds double* %G, i64 %j.02 %tmp3 = load double* %arrayidx %sub = sub i64 %j.02, 1 %arrayidx6 = getelementptr inbounds double* %G, i64 %sub %tmp7 = load double* %arrayidx6 %add = fadd double %tmp3, %tmp7 %arrayidx10 = getelementptr inbounds double* %G, i64 %j.02 store double %add, double* %arrayidx10 %inc = add nsw i64 %j.02, 1 br label %for.cond for.cond: ; preds = %for.body %cmp = icmp slt i64 %inc, 1000 br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge for.cond.for.end_crit_edge: ; preds = %for.cond br label %for.end for.end: ; preds = %for.cond.for.end_crit_edge, %entry ret void } Now we get the much nicer: define void @test(i32 %N, double* %G) nounwind ssp { entry: br label %for.body for.body: ; preds = %entry, %for.body %j.01 = phi i64 [ 1, %entry ], [ %inc, %for.body ] %arrayidx = getelementptr inbounds double* %G, i64 %j.01 %tmp3 = load double* %arrayidx %sub = sub i64 %j.01, 1 %arrayidx6 = getelementptr inbounds double* %G, i64 %sub %tmp7 = load double* %arrayidx6 %add = fadd double %tmp3, %tmp7 %arrayidx10 = getelementptr inbounds double* %G, i64 %j.01 store double %add, double* %arrayidx10 %inc = add nsw i64 %j.01, 1 %cmp = icmp slt i64 %inc, 1000 br i1 %cmp, label %for.body, label %for.end for.end: ; preds = %for.body ret void } With all of these recent changes, we are now able to compile: void foo(char *X) { for (int i = 0; i != 100; ++i) for (int j = 0; j != 100; ++j) X[j+i*100] = 0; } into a single memset of 10000 bytes. This series of changes should also be helpful for other nested loop scenarios as well. llvm-svn: 123079		2011-01-08 19:59:06 +00:00
..
2009-01-25-SingleEntryPhi.ll
basic.ll	Teach loop rotate to hoist trivially invariant instructions	2010-09-06 01:10:22 +00:00
dg.exp
indirectbr.ll
LRCrash-1.ll
LRCrash-2.ll
LRCrash-3.ll
LRCrash-4.ll
LRCrash-5.ll
phi-duplicate.ll	When loop rotation happens, it is *very* common for the duplicated condbr	2011-01-08 19:59:06 +00:00
PhiRename-1.ll
PhiSelfRefernce-1.ll
pr2639.ll
preserve-scev.ll