Author: wmat Date: Mon Feb 11 12:37:34 2008 New Revision: 46959 URL: http://llvm.org/viewvc/llvm-project?rev=46959&view=rev Log: If the LHS of the comparison is a loop-invariant we also want to move it to the RHS. This simple change allows to compute loop iteration count for loops with condition similar to the one in the testcase (which seems to be quite common).
Added: llvm/trunk/test/Analysis/ScalarEvolution/2008-02-11-ReversedCondition.ll Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=46959&r1=46958&r2=46959&view=diff ============================================================================== --- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original) +++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Mon Feb 11 12:37:34 2008 @@ -1819,8 +1819,8 @@ // At this point, we would like to compute how many iterations of the // loop the predicate will return true for these inputs. - if (isa<SCEVConstant>(LHS) && !isa<SCEVConstant>(RHS)) { - // If there is a constant, force it into the RHS. + if (LHS->isLoopInvariant(L) && !RHS->isLoopInvariant(L)) { + // If there is a loop-invariant, force it into the RHS. std::swap(LHS, RHS); Cond = ICmpInst::getSwappedPredicate(Cond); } Added: llvm/trunk/test/Analysis/ScalarEvolution/2008-02-11-ReversedCondition.ll URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/ScalarEvolution/2008-02-11-ReversedCondition.ll?rev=46959&view=auto ============================================================================== --- llvm/trunk/test/Analysis/ScalarEvolution/2008-02-11-ReversedCondition.ll (added) +++ llvm/trunk/test/Analysis/ScalarEvolution/2008-02-11-ReversedCondition.ll Mon Feb 11 12:37:34 2008 @@ -0,0 +1,15 @@ +; RUN: llvm-as < %s | opt -scalar-evolution -analyze | not grep Unpredictable + +define void @foo(i32 %n) { +entry: + br label %header +header: + %i = phi i32 [ 0, %entry ], [ %i.inc, %next ] + %cond = icmp sgt i32 %n, %i + br i1 %cond, label %next, label %return +next: + %i.inc = add i32 %i, 1 + br label %header +return: + ret void +} _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits