mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-12-14 11:32:34 +00:00
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). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46959 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
parent
1f801fa5ad
commit
a089b10421
@ -1819,8 +1819,8 @@ SCEVHandle ScalarEvolutionsImpl::ComputeIterationCount(const Loop *L) {
|
||||
|
||||
// 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);
|
||||
}
|
||||
|
@ -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
|
||||
}
|
Loading…
Reference in New Issue
Block a user