This also required making recursive simplifications until
nothing changes or a hard limit (currently 3) is hit.
With the simplification in place indvars can canonicalize
loops of the form
for (unsigned i = 0; i < a-b; ++i)
into
for (unsigned i = 0; i != a-b; ++i)
which used to fail because SCEV created a weird umax expr
for the backedge taken count.
llvm-svn: 157701
If integer overflow causes one of the terms to reach zero, that can
force the entire expression to zero.
Fixes PR12929: cast<Ty>() argument of incompatible type
llvm-svn: 157673
getUDivExpr attempts to simplify by checking for overflow.
isLoopEntryGuardedByCond then evaluates the loop predicate which
may lead to the same getUDivExpr causing endless recursion.
Fixes PR12868: clang 3.2 segmentation fault.
llvm-svn: 157092
This allows us to keep passing reduced masks to SimplifyDemandedBits, but
know about all the bits if SimplifyDemandedBits fails. This allows instcombine
to simplify cases like the one in the included testcase.
llvm-svn: 154011
instead of its own hard coded thing, allowing it to handle
ConstantDataSequential and fixing some obscure bugs (e.g. it would
previously crash on a CAZ of vector type).
llvm-svn: 148788
bots. Original commit messages:
- Reapply r142781 with fix. Original message:
Enhance SCEV's brute force loop analysis to handle multiple PHI nodes in the
loop header when computing the trip count.
With this, we now constant evaluate:
struct ListNode { const struct ListNode *next; int i; };
static const struct ListNode node1 = {0, 1};
static const struct ListNode node2 = {&node1, 2};
static const struct ListNode node3 = {&node2, 3};
int test() {
int sum = 0;
for (const struct ListNode *n = &node3; n != 0; n = n->next)
sum += n->i;
return sum;
}
- Now that we look at all the header PHIs, we need to consider all the header PHIs
when deciding that the loop has stopped evolving. Fixes miscompile in the gcc
torture testsuite!
llvm-svn: 142919
the dragonegg and llvm-gcc self-host buildbots. Original commit
messages:
- Reapply r142781 with fix. Original message:
Enhance SCEV's brute force loop analysis to handle multiple PHI nodes in the
loop header when computing the trip count.
With this, we now constant evaluate:
struct ListNode { const struct ListNode *next; int i; };
static const struct ListNode node1 = {0, 1};
static const struct ListNode node2 = {&node1, 2};
static const struct ListNode node3 = {&node2, 3};
int test() {
int sum = 0;
for (const struct ListNode *n = &node3; n != 0; n = n->next)
sum += n->i;
return sum;
}
- Now that we look at all the header PHIs, we need to consider all the header PHIs
when deciding that the loop has stopped evolving. Fixes miscompile in the gcc
torture testsuite!
llvm-svn: 142916
able to constant fold load instructions where the argument is a constant.
Second, we should be able to watch multiple PHI nodes through the loop; this
patch only supports PHIs in loop headers, more can be done here.
With this patch, we now constant evaluate:
static const int arr[] = {1, 2, 3, 4, 5};
int test() {
int sum = 0;
for (int i = 0; i < 5; ++i) sum += arr[i];
return sum;
}
llvm-svn: 142731
I noticed during self-review that my previous checkin disabled some
analysis. Even with the reenabled analysis the test case runs in about
5ms. Without the fix, it will take several minutes at least.
llvm-svn: 141164
Note to compiler writers: never recurse on multiple instruction
operands without memoization.
Fixes rdar://10187945. Was taking 45s, now taking 5ms.
llvm-svn: 141161
such.
I'm doing this now for completeness because I can't think of/remember
any reason that it was left out. I'm not sure it will help anything,
but if we don't do it we need to explain why in comments.
llvm-svn: 139450
SCEV unrolling can unroll loops with arbitrary induction variables. It
is a prerequisite for -disable-iv-rewrite performance. It is also
easily handles loops of arbitrary structure including multiple exits
and is generally more robust.
This is under a temporary option to avoid affecting default
behavior for the next couple of weeks. It is needed so that I can
checkin unit tests for updateUnloop.
llvm-svn: 137384
recurrence, the initial values low bits can sometimes be ignored.
To take advantage of this, added FoldIVUser to IndVarSimplify to fold
an IV operand into a udiv/lshr if the operator doesn't affect the
result.
-indvars -disable-iv-rewrite now transforms
i = phi i4
i1 = i0 + 1
idx = i1 >> (2 or more)
i4 = i + 4
into
i = phi i4
idx = i0 >> ...
i4 = i + 4
llvm-svn: 137013
Added a type check in ScalarEvolution::computeSCEVAtScope to handle the case in which operands of an
AddRecExpr in the current scope are folded.
llvm-svn: 130271
SCEV may generate expressions composed of multiple pointers, which can
lead to invalid GEP expansion. Until we can teach SCEV to follow strict
pointer rules, make sure no bad GEPs creep into IR.
Fixes rdar://problem/9038671.
llvm-svn: 127839
properties.
Added the self-wrap flag for SCEV::AddRecExpr.
A slew of temporary FIXMEs indicate the intention of the no-self-wrap flag
without changing behavior in this revision.
llvm-svn: 127590
When ExactBECount is a constant, use it for MaxBECount.
When MaxBECount cannot be computed, replace it with ExactBECount.
Fixes PR9424.
llvm-svn: 127342
unsigned overflow (e.g. "gep P, -1"), and while they can have
signed wrap in theoretical situations, modelling an AddRec as
not having signed wrap is going enough for any case we can
think of today. In the future if this isn't enough, we can
revisit this. Modeling them as having NUW isn't causing any
known problems either FWIW.
llvm-svn: 125410
doesn't return immediately after then the insert position in UniqueSCEVs will
be out of date. No test because this is a memory corruption issue. Fixes PR9051!
llvm-svn: 124282
by indvars through the scev expander.
trunc(add x, y) --> add(trunc x, y). Currently SCEV largely folds the other way
which is probably wrong, but preserved to minimize churn. Instcombine doesn't
do this fold either, demonstrating a missed optz'n opportunity on code doing
add+trunc+add.
llvm-svn: 123838
void f(int* begin, int* end) { std::fill(begin, end, 0); }
which turns into a != exit expression where one pointer is
strided and (thanks to step #1) known to not overflow, and
the other is loop invariant.
The observation here is that, though the IV is strided by
4 in this case, that the IV *has* to become equal to the
end value. It cannot "miss" the end value by stepping over
it, because if it did, the strided IV expression would
eventually wrap around.
Handle this by turning A != B into "A-B != 0" where the A-B
part is known to be NUW.
llvm-svn: 123131
zextOrTrunc(), and APSInt methods extend(), extOrTrunc() and new method
trunc(), to be const and to return a new value instead of modifying the
object in place.
llvm-svn: 121120
preserves LCSSA form out of ScalarEvolution and into the LoopInfo
class. Use it to check that SimplifyInstruction simplifications
are not breaking LCSSA form. Fixes PR8622.
llvm-svn: 119727
needs to be checked that this won't break LCSSA form.
Change the existing checking method to a more direct one:
rather than seeing if all predecessors belong to the loop,
check that the replacing value is either not in any loop or
is in a loop that contains the phi node.
llvm-svn: 119556
must be called in the pass's constructor. This function uses static dependency declarations to recursively initialize
the pass's dependencies.
Clients that only create passes through the createFooPass() APIs will require no changes. Clients that want to use the
CommandLine options for passes will need to manually call the appropriate initialization functions in PassInitialization.h
before parsing commandline arguments.
I have tested this with all standard configurations of clang and llvm-gcc on Darwin. It is possible that there are problems
with the static dependencies that will only be visible with non-standard options. If you encounter any crash in pass
registration/creation, please send the testcase to me directly.
llvm-svn: 116820
perform initialization without static constructors AND without explicit initialization
by the client. For the moment, passes are required to initialize both their
(potential) dependencies and any passes they preserve. I hope to be able to relax
the latter requirement in the future.
llvm-svn: 116334
transformation collect all the addrecs with the same loop
add combine them at once rather than starting everything over
at the first chance.
llvm-svn: 112290
middle, copy the elements in two groups, rather than copying all the
elements and then doing an erase on the middle of the result. These
are SmallVectors, so we shouldn't expect to hit dynamic allocation
in the common case.
llvm-svn: 111151
Andrew Trick