Exactly, that's what I meant to say when I said when loop
conditionals are runtime dependent. To ensure safety in
PromoteValuesInLoop(), one needs to prove that basic-block is executed
at least once. The question is how ?
The most general way to do this is to convert loops like this:
On Sep 19, 2007, at 9:49 AM, Dan Gohman wrote:
Exactly, that's what I meant to say when I said when loop
conditionals are runtime dependent. To ensure safety in
PromoteValuesInLoop(), one needs to prove that basic-block is
executed
at least once. The question is how ?
The most general
On Sep 19, 2007, at 10:49 AM, Devang Patel wrote:
In the second form, code hoisted/sunk/promoted out of the loop will
still be under the guard of the if. Also see tree-ssa-loop-ch.c in
GCC,
for example.
In llvm, loop-rotation pass does this. However, what if LICM input is
not processed
+ // If GEP base is NULL then the calculated address used by Store or
+ // Load instruction is invalid. Do not promote this value because
+ // it may expose load and store instruction that are covered by
+ // condition which may not yet folded.
+ if
We intend to split LICM into three passes - sink, hoist and promote-
values. Irrespective of sinking and hoisting, promote-values should
not promote values that are unsafe. Avoiding hoisting GEP here will
solve this test case, but promote-values bug will be exposed when it
is supplied
On Sep 18, 2007, at 1:51 PM, Dan Gohman wrote:
I don't quite follow. For example of what I'm saying, take this
testcase, which is only slightly different than the earlier one:
define i32 @foo(%struct.decision* %p) {
entry:
br label %blah.i
blah.i:; preds =
It is not safe, because cond_true.i is a dead basic-block. The
question is -- Is it LICM's responsibility to evaluate conditions and
identify dead code or let other passes handle this earlier?. For
example here, instruction combiner will fold comparison and cfg
simplifier will take
On Sep 18, 2007, at 3:38 PM, Dan Gohman wrote:
Ok, so let's tweak the testcase again:
define i32 @foo(%struct.decision* %p, %struct.decision* %q) {
entry:
br label %blah.i
blah.i:; preds = %cond_true.i, %entry
%tmp3.i = icmp eq %struct.decision* null, %q
