by using llvm::isIdentifiedObject. Also teach it to handle GEPs that have
the same base pointer and constant operands. Fixes PR11238!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151449 91177308-0d34-0410-b5e6-96231b3b80d8
the dominance once the dominates method is fixed and why we can use the builder's
insertion point.
Fixes pr12048.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151125 91177308-0d34-0410-b5e6-96231b3b80d8
know where users will be added. Because of this, it cannot use
Builder.GetInsertPoint at all.
This patch
* removes the FIXME about adding the assert.
* adds a comment explaining hy we don't have one.
* removes a broken logic that only works for some callers and is not needed
since r150884.
* adds an assert to caller that would have caught the bug fixed by r150884.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151015 91177308-0d34-0410-b5e6-96231b3b80d8
the cast. If we do, we can end up with
inst1
--------------- < Insertion point
dbg inst
new inst
instead of the desired
inst1
new inst
--------------- < Insertion point
dbg inst
Another option would be for InsertNoopCastOfTo (or its callers) to move the
insertion point and we would end up with
inst1
dbg inst
new inst
--------------- < Insertion point
but that complicates the callers. This fixes PR12018 (and firefox's build).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150884 91177308-0d34-0410-b5e6-96231b3b80d8
actually work, at least as described. LLVM Metadata is not
intended to suppress LLVM IR rules, as it can be stripped at
any time.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150821 91177308-0d34-0410-b5e6-96231b3b80d8
but with a critical fix to the SelectionDAG code that optimizes copies
from strings into immediate stores: the previous code was stopping reading
string data at the first nul. Address this by adding a new argument to
llvm::getConstantStringInfo, preserving the behavior before the patch.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149800 91177308-0d34-0410-b5e6-96231b3b80d8
The purpose of refactoring is to hide operand roles from SwitchInst user (programmer). If you want to play with operands directly, probably you will need lower level methods than SwitchInst ones (TerminatorInst or may be User). After this patch we can reorganize SwitchInst operands and successors as we want.
What was done:
1. Changed semantics of index inside the getCaseValue method:
getCaseValue(0) means "get first case", not a condition. Use getCondition() if you want to resolve the condition. I propose don't mix SwitchInst case indexing with low level indexing (TI successors indexing, User's operands indexing), since it may be dangerous.
2. By the same reason findCaseValue(ConstantInt*) returns actual number of case value. 0 means first case, not default. If there is no case with given value, ErrorIndex will returned.
3. Added getCaseSuccessor method. I propose to avoid usage of TerminatorInst::getSuccessor if you want to resolve case successor BB. Use getCaseSuccessor instead, since internal SwitchInst organization of operands/successors is hidden and may be changed in any moment.
4. Added resolveSuccessorIndex and resolveCaseIndex. The main purpose of these methods is to see how case successors are really mapped in TerminatorInst.
4.1 "resolveSuccessorIndex" was created if you need to level down from SwitchInst to TerminatorInst. It returns TerminatorInst's successor index for given case successor.
4.2 "resolveCaseIndex" converts low level successors index to case index that curresponds to the given successor.
Note: There are also related compatability fix patches for dragonegg, klee, llvm-gcc-4.0, llvm-gcc-4.2, safecode, clang.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149481 91177308-0d34-0410-b5e6-96231b3b80d8
kicking in the big win of ConstantDataArray. As part of this, change
the implementation of GetConstantStringInfo in ValueTracking to work
with ConstantDataArray (and not ConstantArray) making it dramatically,
amazingly, more efficient in the process and renaming it to
getConstantStringInfo.
This keeps around a GetConstantStringInfo entrypoint that (grossly)
forwards to getConstantStringInfo and constructs the std::string
required, but existing clients should move over to
getConstantStringInfo instead.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149351 91177308-0d34-0410-b5e6-96231b3b80d8
Unfortunately I also had to disable constant-pool-sharing.ll the code it tests has been
updated to use the IL logic.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149148 91177308-0d34-0410-b5e6-96231b3b80d8
we're at it, allow PatternMatch's "neg" pattern to match integer
vector negations, and enhance ComputeNumSigned bits to handle
shl of vectors.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149082 91177308-0d34-0410-b5e6-96231b3b80d8
savings from a pointer argument becoming an alloca. Sometimes callees will even
compare a pointer to null and then branch to an otherwise unreachable block!
Detect these cases and compute the number of saved instructions, instead of
bailing out and reporting no savings.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148941 91177308-0d34-0410-b5e6-96231b3b80d8
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).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148788 91177308-0d34-0410-b5e6-96231b3b80d8
out into a new ConstantFoldLoadThroughGEPIndices (more useful) function
and rewrite it to be simpler, more efficient, and to handle the new
ConstantDataSequential type.
Enhance ConstantFoldLoadFromConstPtr to handle ConstantDataSequential.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148786 91177308-0d34-0410-b5e6-96231b3b80d8
can't handle. Also don't produce non-zero results for things which won't be
transformed by SROA at all just because we saw the loads/stores before we saw
the use of the address.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148536 91177308-0d34-0410-b5e6-96231b3b80d8
LSR has gradually been improved to more aggressively reuse existing code, particularly existing phi cycles. This exposed problems with the SCEVExpander's sloppy treatment of its insertion point. I applied some rigor to the insertion point problem that will hopefully avoid an endless bug cycle in this area. Changes:
- Always used properlyDominates to check safe code hoisting.
- The insertion point provided to SCEV is now considered a lower bound. This is usually a block terminator or the use itself. Under no cirumstance may SCEVExpander insert below this point.
- LSR is reponsible for finding a "canonical" insertion point across expansion of different expressions.
- Robust logic to determine whether IV increments are in "expanded" form and/or can be safely hoisted above some insertion point.
Fixes PR11783: SCEVExpander assert.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148535 91177308-0d34-0410-b5e6-96231b3b80d8
need to make a deep copy of each of the std::maps. Use a std::map of the
std::map instead. This improves the compile time of sqlite3 by ~2%.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148003 91177308-0d34-0410-b5e6-96231b3b80d8
These heuristics are sufficient for enabling IV chains by
default. Performance analysis has been done for i386, x86_64, and
thumbv7. The optimization is rarely important, but can significantly
speed up certain cases by eliminating spill code within the
loop. Unrolled loops are prime candidates for IV chains. In many
cases, the final code could still be improved with more target
specific optimization following LSR. The goal of this feature is for
LSR to make the best choice of induction variables.
Instruction selection may not completely take advantage of this
feature yet. As a result, there could be cases of slight code size
increase.
Code size can be worse on x86 because it doesn't support postincrement
addressing. In fact, when chains are formed, you may see redundant
address plus stride addition in the addressing mode. GenerateIVChains
tries to compensate for the common cases.
On ARM, code size increase can be mitigated by using postincrement
addressing, but downstream codegen currently misses some opportunities.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147826 91177308-0d34-0410-b5e6-96231b3b80d8
captured. This allows the tracker to look at the specific use, which may be
especially interesting for function calls.
Use this to fix 'nocapture' deduction in FunctionAttrs. The existing one does
not iterate until a fixpoint and does not guarantee that it produces the same
result regardless of iteration order. The new implementation builds up a graph
of how arguments are passed from function to function, and uses a bottom-up walk
on the argument-SCCs to assign nocapture. This gets us nocapture more often, and
does so rather efficiently and independent of iteration order.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147327 91177308-0d34-0410-b5e6-96231b3b80d8
unsigned foo(unsigned x) { return 31 - __builtin_clz(x); }
now compiles into a single "bsrl" instruction on x86.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147255 91177308-0d34-0410-b5e6-96231b3b80d8
probability wouldn't be considered "hot" in some weird loop structures
or other compounding probability patterns. This makes it much harder to
confuse, but isn't really a principled fix. I'd actually like it if we
could model a zero probability, as it would make this much easier to
reason about. Suggestions for how to do this better are welcome.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147142 91177308-0d34-0410-b5e6-96231b3b80d8
call site of an intrinsic is also not an inline candidate. While here, make it
more obvious that this code ignores all intrinsics. Noticed by inspection!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147037 91177308-0d34-0410-b5e6-96231b3b80d8
pointer or a reference type - we actually just want the size of the
pointer then for that.
Fixes rdar://10335756
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146785 91177308-0d34-0410-b5e6-96231b3b80d8
into Analysis as a standalone function, since there's no need for
it to be in VMCore. Also, update it to use isKnownNonZero and
other goodies available in Analysis, making it more precise,
enabling more aggressive optimization.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146610 91177308-0d34-0410-b5e6-96231b3b80d8
subdirectories to traverse into.
- Originally I wanted to avoid this and just autoscan, but this has one key
flaw in that new subdirectories can not automatically trigger a rerun of the
llvm-build tool. This is particularly a pain when switching back and forth
between trees where one has added a subdirectory, as the dependencies will
tend to be wrong. This will also eliminates FIXME implicitly.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146436 91177308-0d34-0410-b5e6-96231b3b80d8
indicates whether the intrinsic has a defined result for a first
argument equal to zero. This will eventually allow these intrinsics to
accurately model the semantics of GCC's __builtin_ctz and __builtin_clz
and the X86 instructions (prior to AVX) which implement them.
This patch merely sets the stage by extending the signature of these
intrinsics and establishing auto-upgrade logic so that the old spelling
still works both in IR and in bitcode. The upgrade logic preserves the
existing (inefficient) semantics. This patch should not change any
behavior. CodeGen isn't updated because it can use the existing
semantics regardless of the flag's value.
Note that this will be followed by API updates to Clang and DragonEgg.
Reviewed by Nick Lewycky!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146357 91177308-0d34-0410-b5e6-96231b3b80d8
don't do this now, but add a test case to prevent this from happening in the
future.
Additional test for rdar://9892684
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145879 91177308-0d34-0410-b5e6-96231b3b80d8
-15% on ARMDisassembler.cpp (Release build). It's not that great to add another
layer of caching to the caching-heavy LVI but I don't see a better way.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145770 91177308-0d34-0410-b5e6-96231b3b80d8
weak variable are compiled by different compilers, such as GCC and LLVM, while
LLVM may increase the alignment to the preferred alignment there is no reason to
think that GCC will use anything more than the ABI alignment. Since it is the
GCC version that might end up in the final program (as the linkage is weak), it
is wrong to increase the alignment of loads from the global up to the preferred
alignment as the alignment might only be the ABI alignment.
Increasing alignment up to the ABI alignment might be OK, but I'm not totally
convinced that it is. It seems better to just leave the alignment of weak
globals alone.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145413 91177308-0d34-0410-b5e6-96231b3b80d8
and positive: positive, because it could be directly computed to be positive;
negative, because the nsw flags means it is either negative or undefined (the
multiplication always overflowed).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145104 91177308-0d34-0410-b5e6-96231b3b80d8
The loop tree's inclusive block lists are painful and expensive to
update. (I have no idea why they're inclusive). The design was
supposed to handle this case but the implementation missed it and my
unit tests weren't thorough enough.
Fixes PR11335: loop unroll update.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144970 91177308-0d34-0410-b5e6-96231b3b80d8
and stores capture) to permit the caller to see each capture point and decide
whether to continue looking.
Use this inside memdep to do an analysis that basicaa won't do. This lets us
solve another devirtualization case, fixing PR8908!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144580 91177308-0d34-0410-b5e6-96231b3b80d8
with the given predicate, it matches any condition and returns the
predicate - d'oh! Original commit message:
The expression icmp eq (select (icmp eq x, 0), 1, x), 0 folds to false.
Spotted by my super-optimizer in 186.crafty and 450.soplex. We really
need a proper infrastructure for handling generalizations of this kind
of thing (which occur a lot), however this case is so simple that I decided
to go ahead and implement it directly.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143318 91177308-0d34-0410-b5e6-96231b3b80d8
Spotted by my super-optimizer in 186.crafty and 450.soplex. We really
need a proper infrastructure for handling generalizations of this kind
of thing (which occur a lot), however this case is so simple that I decided
to go ahead and implement it directly.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143214 91177308-0d34-0410-b5e6-96231b3b80d8
using BinaryOperator (which only works for instructions) when it should have
been a cast to OverflowingBinaryOperator (which also works for constants).
While there, correct a few other dubious looking uses of BinaryOperator.
Thanks to Chad Rosier for the testcase. Original commit message:
My super-optimizer noticed that we weren't folding this expression to
true: (x *nsw x) sgt 0, where x = (y | 1). This occurs in 464.h264ref.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143125 91177308-0d34-0410-b5e6-96231b3b80d8
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!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142919 91177308-0d34-0410-b5e6-96231b3b80d8
classifying many edges as exiting which were in fact not. These mainly
formed edges into sub-loops. It was also not correctly classifying all
returning edges out of loops as leaving the loop. With this match most
of the loop heuristics are more rational.
Several serious regressions on loop-intesive benchmarks like perlbench's
loop tests when built with -enable-block-placement are fixed by these
updated heuristics. Unfortunately they in turn uncover some other
regressions. There are still several improvemenst that should be made to
loop heuristics including trip-count, and early back-edge management.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142917 91177308-0d34-0410-b5e6-96231b3b80d8
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!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142916 91177308-0d34-0410-b5e6-96231b3b80d8
introduce no-return or unreachable heuristics.
The return heuristics from the Ball and Larus paper don't work well in
practice as they pessimize early return paths. The only good hitrate
return heuristics are those for:
- NULL return
- Constant return
- negative integer return
Only the last of these three can possibly require significant code for
the returning block, and even the last is fairly rare and usually also
a constant. As a consequence, even for the cold return paths, there is
little code on that return path, and so little code density to be gained
by sinking it. The places where sinking these blocks is valuable (inner
loops) will already be weighted appropriately as the edge is a loop-exit
branch.
All of this aside, early returns are nearly as common as all three of
these return categories, and should actually be predicted as taken!
Rather than muddy the waters of the static predictions, just remain
silent on returns and let the CFG itself dictate any layout or other
issues.
However, the return heuristic was flagging one very important case:
unreachable. Unfortunately it still gave a 1/4 chance of the
branch-to-unreachable occuring. It also didn't do a rigorous job of
finding those blocks which post-dominate an unreachable block.
This patch builds a more powerful analysis that should flag all branches
to blocks known to then reach unreachable. It also has better worst-case
runtime complexity by not looping through successors for each block. The
previous code would perform an N^2 walk in the event of a single entry
block branching to N successors with a switch where each successor falls
through to the next and they finally fall through to a return.
Test case added for noreturn heuristics. Also doxygen comments improved
along the way.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142793 91177308-0d34-0410-b5e6-96231b3b80d8
state. Furthermore, they might not have two operands. This fixes the underlying
issue behind the crashes introduced in r142781.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142788 91177308-0d34-0410-b5e6-96231b3b80d8
Assertion `i_nocapture < OperandTraits<PHINode>::operands(this) && "getOperand() out of range!"' failed.
coming out of indvars.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142786 91177308-0d34-0410-b5e6-96231b3b80d8
a single class. Previously it was split between two classes, one
internal and one external. The concern seemed to center around exposing
the weights used, but those can remain confined to the implementation
file.
Having a single class to maintain the state and analyses in use will
also simplify several of the enhancements I want to make to our static
heuristics.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142783 91177308-0d34-0410-b5e6-96231b3b80d8
extraneous whitespace. Trying to clean-up this pass as much as I can
before I start making functional changes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142780 91177308-0d34-0410-b5e6-96231b3b80d8
to bring it under direct test instead of merely indirectly testing it in
the BlockFrequencyInfo pass.
The next step is to start adding tests for the various heuristics
employed, and to start fixing those heuristics once they're under test.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142778 91177308-0d34-0410-b5e6-96231b3b80d8
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;
}
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142731 91177308-0d34-0410-b5e6-96231b3b80d8
and switches, with arbitrary numbers of successors. Still optimized for
the common case of 2 successors for a conditional branch.
Add a test case for switch metadata showing up in the BlockFrequencyInfo pass.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142493 91177308-0d34-0410-b5e6-96231b3b80d8
encoding of probabilities. In the absense of metadata, it continues to
fall back on static heuristics.
This allows __builtin_expect, after lowering through llvm.expect
a branch instruction's metadata, to actually enter the branch
probability model. This is one component of resolving PR2577.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142492 91177308-0d34-0410-b5e6-96231b3b80d8
layer already had support for printing the results of this analysis, but
the wiring was missing.
Now that printing the analysis works, actually bring some of this
analysis, and the BranchProbabilityInfo analysis that it wraps, under
test! I'm planning on fixing some bugs and doing other work here, so
having a nice place to add regression tests and a way to observe the
results is really useful.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142491 91177308-0d34-0410-b5e6-96231b3b80d8
Some code want to check that *any* call within a function has the 'returns
twice' attribute, not just that the current function has one.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142221 91177308-0d34-0410-b5e6-96231b3b80d8
Just because we're dealing with a GEP doesn't mean we can assert the
SCEV has a pointer type. The fix is simply to ignore the SCEV pointer
type, which we really didn't need.
Fixes PR11138 webkit crash.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142058 91177308-0d34-0410-b5e6-96231b3b80d8
could be arguments, for example.
No testcase because this is a bug-fix broken out of a larger optimization patch.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141951 91177308-0d34-0410-b5e6-96231b3b80d8
Speculatively reapply to see if this test case still crashes on
linux. I may have fixed it in my last checkin.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141895 91177308-0d34-0410-b5e6-96231b3b80d8
This avoids unnecessary expansion of expressions and allows the SCEV
expander to work on expression DAGs, not just trees.
Fixes PR11090.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141870 91177308-0d34-0410-b5e6-96231b3b80d8
file. Since it should only be used when necessary propagate it through
the backend code generation and tweak testcases accordingly.
This helps with code like in clang's test/CodeGen/debug-info-line.c where
we have multiple #line directives within a single lexical block and want
to generate only a single block that contains each file change.
Part of rdar://10246360
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141729 91177308-0d34-0410-b5e6-96231b3b80d8
IVs.
Indvars previously chose randomly between congruent IVs. Now it will
bias the decision toward IVs that SCEVExpander likes to create. This
was not done to fix any problem, it's just a welcome side effect of
factoring code.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141633 91177308-0d34-0410-b5e6-96231b3b80d8
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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141164 91177308-0d34-0410-b5e6-96231b3b80d8
Note to compiler writers: never recurse on multiple instruction
operands without memoization.
Fixes rdar://10187945. Was taking 45s, now taking 5ms.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141161 91177308-0d34-0410-b5e6-96231b3b80d8
We want heuristics to be based on accurate data, but more importantly
we don't want llvm to behave randomly. A benign trunc inserted by an
upstream pass should not cause a wild swings in optimization
level. See PR11034. It's a general problem with threshold-based
heuristics, but we can make it less bad.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140919 91177308-0d34-0410-b5e6-96231b3b80d8
