Fix the PendingQueue, then disable it because it's not required for
the current schedulers' heuristics.
Fix the logic for the unused list-ilp scheduler.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126981 91177308-0d34-0410-b5e6-96231b3b80d8
it. It's been assumed up til now that it would be in its immediate
successor. However, this isn't necessarily the case. It could be in one of its
successor's successors.
Modify the code to more thoroughly check for an 'eh.selector' call in
successors. It only looks at a successor if we get there as a result of an
unconditional branch.
Testcase ObjC/exceptions-4.m in r126968.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126969 91177308-0d34-0410-b5e6-96231b3b80d8
David Greene changed CannotYetSelect() to print the full DAG including multiple
copies of operands reached through different paths in the DAG. Unfortunately
this blows up exponentially in some cases. The depth limit of 100 is way too
high to prevent this -- I'm seeing a message string of 150MB with a depth of
only 40 in one particularly bad case, even though the DAG has less than 200
nodes. Part of the problem is that the printing code is following chain
operands, so if you fail to select an operation with a chain, the printer will
follow all the chained operations back to the entry node.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126899 91177308-0d34-0410-b5e6-96231b3b80d8
1. Inform users of ADDEs with two 0 operands that it never sets carry
2. Fold other ADDs or ADDCs into the ADDE if possible
It would be neat if we could do the same thing for SETCC+ADD eventually, but we can't do that in target independent code.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126557 91177308-0d34-0410-b5e6-96231b3b80d8
is possible to do better if the high bit is set in either KnownZero/KnownOne, but
in practice NumSignBits is always 1 when we are zero extending because nothing
is known about that register.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126465 91177308-0d34-0410-b5e6-96231b3b80d8
Limit the folding of any_ext and sext into the load operation to scalars.
Limit the active-bits trunc optimization to scalars.
Document vector trunc and vector sext in LangRef.
Similar to commit 126080 (for enabling zext).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126424 91177308-0d34-0410-b5e6-96231b3b80d8
registers at phis. This enables us to eliminate a lot of pointless zexts during
the DAGCombine phase. This fixes <rdar://problem/8760114>.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126380 91177308-0d34-0410-b5e6-96231b3b80d8
at phis. This enables us to eliminate a lot of pointless zexts during the DAGCombine
phase. This fixes <rdar://problem/8760114>.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126170 91177308-0d34-0410-b5e6-96231b3b80d8
In other words, do not keep track of argument's location. The debugger (gdb) is not prepared to see line table entries for arguments. For the debugger, "second" line table entry marks beginning of function body.
This requires some coordination with debugger to get this working.
- The debugger needs to be aware of prolog_end attribute attached with line table entries.
- The compiler needs to accurately mark prolog_end in line table entries (at -O0 and at -O1+)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126155 91177308-0d34-0410-b5e6-96231b3b80d8
The DAGCombiner folds the zext into complex load instructions. This patch
prevents this optimization on vectors since none of the supported targets
knows how to perform load+vector_zext in one instruction.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126080 91177308-0d34-0410-b5e6-96231b3b80d8
the time but presumably my email got lost). Examples where the previous logic
got it wrong: (1) a signed i8 multiply of 64 by 2 overflows, but the high part is
zero; (2) a signed i8 multiple of -128 by 2 overflows, but the high part is all
ones.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125748 91177308-0d34-0410-b5e6-96231b3b80d8
transformation if we can't legally create a build vector of the correct
type. Check that we can make the transformation first, and add a TODO to
refactor this code with similar cases.
Fixes: PR9223 and rdar://9000350
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125631 91177308-0d34-0410-b5e6-96231b3b80d8
have their low bits set to zero. This allows us to optimize
out explicit stack alignment code like in stack-align.ll:test4 when
it is redundant.
Doing this causes the code generator to start turning FI+cst into
FI|cst all over the place, which is general goodness (that is the
canonical form) except that various pieces of the code generator
don't handle OR aggressively. Fix this by introducing a new
SelectionDAG::isBaseWithConstantOffset predicate, and using it
in places that are looking for ADD(X,CST). The ARM backend in
particular was missing a lot of addressing mode folding opportunities
around OR.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125470 91177308-0d34-0410-b5e6-96231b3b80d8
generating i8 shift amounts for things like i1024 types. Add
an assert in getNode to prevent this from occuring in the future,
fix the buggy transformation, revert my previous patch, and
document this gotcha in ISDOpcodes.h
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125465 91177308-0d34-0410-b5e6-96231b3b80d8
the shift amounts are in a suitably wide type so that
we don't generate out of range constant shift amounts.
This fixes PR9028.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125458 91177308-0d34-0410-b5e6-96231b3b80d8
is narrower than the shift register. Doing an anyext provides undefined bits in
the top part of the register.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125457 91177308-0d34-0410-b5e6-96231b3b80d8
The DAGCombiner created illegal BUILD_VECTOR operations.
The patch added a check that either illegal operations are
allowed or that the created operation is legal.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125435 91177308-0d34-0410-b5e6-96231b3b80d8
The bug happens when the DAGCombiner attempts to optimize one of the patterns
of the SUB opcode. It tries to create a zero of type v2i64. This type is legal
on 32bit machines, but the initializer of this vector (i64) is target dependent.
Currently, the initializer attempts to create an i64 zero constant, which fails.
Added a flag to tell the DAGCombiner to create a legal zero, if we require that
the pass would generate legal types.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125391 91177308-0d34-0410-b5e6-96231b3b80d8
precisely track pressure on a selection DAG, but we can at least keep
it balanced. This design accounts for various interesting aspects of
selection DAGS: register and subregister copies, glued nodes, dead
nodes, unused registers, etc.
Added SUnit::NumRegDefsLeft and ScheduleDAGSDNodes::RegDefIter.
Note: I disabled PrescheduleNodesWithMultipleUses when register
pressure is enabled, based on no evidence other than I don't think it
makes sense to have both enabled.
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the load, then it may be legal to transform the load and store to integer
load and store of the same width.
This is done if the target specified the transformation as profitable. e.g.
On arm, this can transform:
vldr.32 s0, []
vstr.32 s0, []
to
ldr r12, []
str r12, []
rdar://8944252
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This happens all the time when a smul is promoted to a larger type.
On x86-64 we now compile "int test(int x) { return x/10; }" into
movslq %edi, %rax
imulq $1717986919, %rax, %rax
movq %rax, %rcx
shrq $63, %rcx
sarq $34, %rax <- used to be "shrq $32, %rax; sarl $2, %eax"
addl %ecx, %eax
This fires 96 times in gcc.c on x86-64.
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This happens e.g. for code like "X - X%10" where we lower the modulo operation
to a series of multiplies and shifts that are then subtracted from X, leading to
this missed optimization.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124532 91177308-0d34-0410-b5e6-96231b3b80d8
default implementation for x86, going through the stack in a similr
fashion to how the codegen implements BUILD_VECTOR. Eventually this
will get matched to VINSERTF128 if AVX is available.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124307 91177308-0d34-0410-b5e6-96231b3b80d8
implementation of EXTRACT_SUBVECTOR for x86, going through the stack
in a similr fashion to how the codegen implements BUILD_VECTOR.
Eventually this will get matched to VEXTRACTF128 if AVX is available.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124292 91177308-0d34-0410-b5e6-96231b3b80d8
clang's -Wuninitialized-experimental warning.
While these don't look like real bugs, clang's
-Wuninitialized-experimental analysis is stricter
than GCC's, and these fixes have the benefit
of being general nice cleanups.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124073 91177308-0d34-0410-b5e6-96231b3b80d8
DAG. Disable using "-disable-sched-cycles".
For ARM, this enables a framework for modeling the cpu pipeline and
counting stalls. It also activates several heuristics to drive
scheduling based on the model. Scheduling is inherently imprecise at
this stage, and until spilling is improved it may defeat attempts to
schedule. However, this framework provides greater control over
tuning codegen.
Although the flag is not target-specific, it should have very little
affect on the default scheduler used by x86. The only two changes that
affect x86 are:
- scheduling a high-latency operation bumps the current cycle so independent
operations can have their latency covered. i.e. two independent 4
cycle operations can produce results in 4 cycles, not 8 cycles.
- Two operations with equal register pressure impact and no
latency-based stalls on their uses will be prioritized by depth before height
(height is irrelevant if no stalls occur in the schedule below this point).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123971 91177308-0d34-0410-b5e6-96231b3b80d8
flags. They are still not enable in this revision.
Added TargetInstrInfo::isZeroCost() to fix a fundamental problem with
the scheduler's model of operand latency in the selection DAG.
Generalized unit tests to work with sched-cycles.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123969 91177308-0d34-0410-b5e6-96231b3b80d8
to add/sub by doing the normal operation and then checking for overflow
afterwards. This generally relies on the DAG handling the later invalid
operations as well.
Fixes the 64-bit part of rdar://8622122 and rdar://8774702.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123908 91177308-0d34-0410-b5e6-96231b3b80d8
Added a check for already live regs before claiming HighRegPressure.
Fixed a few cases of checking the wrong number of successors.
Added some tracing until these heuristics are better understood.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123892 91177308-0d34-0410-b5e6-96231b3b80d8
with an invalid type then split the result and perform the overflow check
normally.
Fixes the 32-bit parts of rdar://8622122 and rdar://8774702.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123864 91177308-0d34-0410-b5e6-96231b3b80d8
This shaves off 4 popcounts from the hacked 186.crafty source.
This is enabled even when a native popcount instruction is available. The
combined code is one operation longer but it should be faster nevertheless.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123621 91177308-0d34-0410-b5e6-96231b3b80d8
http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
In a silly microbenchmark on a 65 nm core2 this is 1.5x faster than the old
code in 32 bit mode and about 2x faster in 64 bit mode. It's also a lot shorter,
especially when counting 64 bit population on a 32 bit target.
I hope this is fast enough to replace Kernighan-style counting loops even when
the input is rather sparse.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123547 91177308-0d34-0410-b5e6-96231b3b80d8
disabled in this checkin. Sorry for the large diffs due to
refactoring. New functionality is all guarded by EnableSchedCycles.
Scheduling the isel DAG is inherently imprecise, but we give it a best
effort:
- Added MayReduceRegPressure to allow stalled nodes in the queue only
if there is a regpressure need.
- Added BUHasStall to allow checking for either dependence stalls due to
latency or resource stalls due to pipeline hazards.
- Added BUCompareLatency to encapsulate and standardize the heuristics
for minimizing stall cycles (vs. reducing register pressure).
- Modified the bottom-up heuristic (now in BUCompareLatency) to
prioritize nodes by their depth rather than height. As long as it
doesn't stall, height is irrelevant. Depth represents the critical
path to the DAG root.
- Added hybrid_ls_rr_sort::isReady to filter stalled nodes before
adding them to the available queue.
Related Cleanup: most of the register reduction routines do not need
to be templates.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123468 91177308-0d34-0410-b5e6-96231b3b80d8
There's an inherent tension in DAGCombine between assuming
that things will be put in canonical form, and the Depth
mechanism that disables transformations when recursion gets
too deep. It would not surprise me if there's a lot of little
bugs like this one waiting to be discovered. The mechanism
seems fragile and I'd suggest looking at it from a design viewpoint.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123191 91177308-0d34-0410-b5e6-96231b3b80d8
These functions not longer assert when passed 0, but simply return false instead.
No functional change intended.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123155 91177308-0d34-0410-b5e6-96231b3b80d8
Print virtual registers numbered from 0 instead of the arbitrary
FirstVirtualRegister. The first virtual register is printed as %vreg0.
TRI::NoRegister is printed as %noreg.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123107 91177308-0d34-0410-b5e6-96231b3b80d8
Instead encode llvm IR level property "HasSideEffects" in an operand (shared
with IsAlignStack). Added MachineInstrs::hasUnmodeledSideEffects() to check
the operand when the instruction is an INLINEASM.
This allows memory instructions to be moved around INLINEASM instructions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123044 91177308-0d34-0410-b5e6-96231b3b80d8
Also fix an off-by-one in SelectionDAGBuilder that was preventing shuffle
vectors from being translated to EXTRACT_SUBVECTOR.
Patch by Tim Northover.
The test changes are needed to keep those spill-q tests from testing aligned
spills and restores. If the only aligned stack objects are spill slots, we
no longer realign the stack frame. Prior to this patch, an EXTRACT_SUBVECTOR
was legalized by loading from the stack, which created an aligned frame index.
Now, however, there is nothing except the spill slot in the stack frame, so
I added an aligned alloca.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122995 91177308-0d34-0410-b5e6-96231b3b80d8
We were never generating any of these nodes with variable indices, and there
was one legalizer function asserting on a non-constant index. If we ever have
a need to support variable indices, we can add this back again.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122993 91177308-0d34-0410-b5e6-96231b3b80d8
etc. takes an option OptSize. If OptSize is true, it would return
the inline limit for functions with attribute OptSize.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122952 91177308-0d34-0410-b5e6-96231b3b80d8
up freebsd bootloader. However, this doesn't make much sense for Darwin, whose
-Os is meant to optimize for size only if it doesn't hurt performance.
rdar://8821501
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This allows us to compile:
void test(char *s, int a) {
__builtin_memset(s, a, 15);
}
into 1 mul + 3 stores instead of 3 muls + 3 stores.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122710 91177308-0d34-0410-b5e6-96231b3b80d8
We could implement a DAGCombine to turn x * 0x0101 back into logic operations
on targets that doesn't support the multiply or it is slow (p4) if someone cares
enough.
Example code:
void test(char *s, int a) {
__builtin_memset(s, a, 4);
}
before:
_test: ## @test
movzbl 8(%esp), %eax
movl %eax, %ecx
shll $8, %ecx
orl %eax, %ecx
movl %ecx, %eax
shll $16, %eax
orl %ecx, %eax
movl 4(%esp), %ecx
movl %eax, 4(%ecx)
movl %eax, (%ecx)
ret
after:
_test: ## @test
movzbl 8(%esp), %eax
imull $16843009, %eax, %eax ## imm = 0x1010101
movl 4(%esp), %ecx
movl %eax, 4(%ecx)
movl %eax, (%ecx)
ret
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122707 91177308-0d34-0410-b5e6-96231b3b80d8
DAG scheduling during isel. Most new functionality is currently
guarded by -enable-sched-cycles and -enable-sched-hazard.
Added InstrItineraryData::IssueWidth field, currently derived from
ARM itineraries, but could be initialized differently on other targets.
Added ScheduleHazardRecognizer::MaxLookAhead to indicate whether it is
active, and if so how many cycles of state it holds.
Added SchedulingPriorityQueue::HasReadyFilter to allowing gating entry
into the scheduler's available queue.
ScoreboardHazardRecognizer now accesses the ScheduleDAG in order to
get information about it's SUnits, provides RecedeCycle for bottom-up
scheduling, correctly computes scoreboard depth, tracks IssueCount, and
considers potential stall cycles when checking for hazards.
ScheduleDAGRRList now models machine cycles and hazards (under
flags). It tracks MinAvailableCycle, drives the hazard recognizer and
priority queue's ready filter, manages a new PendingQueue, properly
accounts for stall cycles, etc.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122541 91177308-0d34-0410-b5e6-96231b3b80d8
In the bottom-up selection DAG scheduling, handle two-address
instructions that read/write unspillable registers. Treat
the entire chain of two-address nodes as a single live range.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122472 91177308-0d34-0410-b5e6-96231b3b80d8
loads properly. We miscompiled the testcase into:
_test: ## @test
movl $128, (%rdi)
movzbl 1(%rdi), %eax
ret
Now we get a proper:
_test: ## @test
movl $128, (%rdi)
movsbl (%rdi), %eax
movzbl %ah, %eax
ret
This fixes PR8757.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122392 91177308-0d34-0410-b5e6-96231b3b80d8
the shift type was needed one place, the shift count
type another. The transform in 123555 had the same
problem.
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count operand. These should be the same but apparently are
not always, and this is cleaner anyway. This improves the
code in an existing test.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122354 91177308-0d34-0410-b5e6-96231b3b80d8
ARM (and other 32-bit-only) targets support for i8 and i16 overflow
multiplies. The generated code isn't great, but this at least fixes
CodeGen/Generic/overflow.ll when running on ARM hosts.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122221 91177308-0d34-0410-b5e6-96231b3b80d8
Imagine we see:
EFLAGS = inst1
EFLAGS = inst2 FLAGS
gpr = inst3 EFLAGS
Previously, we would refuse to schedule inst2 because it clobbers
the EFLAGS of the predecessor. However, it also uses the EFLAGS
of the predecessor, so it is safe to emit. SDep edges ensure that
the right order happens already anyway.
This fixes 2 testsuite crashes with the X86 patch I'm going to
commit next.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122211 91177308-0d34-0410-b5e6-96231b3b80d8
isel is *required* to split the edge. PHI values get evaluated
on the edge, not in their predecessor block.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122170 91177308-0d34-0410-b5e6-96231b3b80d8
BUILD_VECTOR operands where the element type is not legal. I had previously
changed this code to insert TRUNCATE operations, but that was just wrong.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122102 91177308-0d34-0410-b5e6-96231b3b80d8
when the wider type is legal. This allows us to compile:
define zeroext i16 @test1(i16 zeroext %x) nounwind {
entry:
%div = udiv i16 %x, 33
ret i16 %div
}
into:
test1: # @test1
movzwl 4(%esp), %eax
imull $63551, %eax, %eax # imm = 0xF83F
shrl $21, %eax
ret
instead of:
test1: # @test1
movw $-1985, %ax # imm = 0xFFFFFFFFFFFFF83F
mulw 4(%esp)
andl $65504, %edx # imm = 0xFFE0
movl %edx, %eax
shrl $5, %eax
ret
Implementing rdar://8760399 and example #4 from:
http://blog.regehr.org/archives/320
We should implement the same thing for [su]mul_hilo, but I don't
have immediate plans to do this.
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catch this here rather than later after accessing uninitialized memory
etc. Fires when compiling the testcase in PR8237.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121635 91177308-0d34-0410-b5e6-96231b3b80d8
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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121120 91177308-0d34-0410-b5e6-96231b3b80d8
legalization time. Since at legalization time there is no mapping from
SDNode back to the corresponding LLVM instruction and the return
SDNode is target specific, this requires a target hook to check for
eligibility. Only x86 and ARM support this form of sibcall optimization
right now.
rdar://8707777
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120501 91177308-0d34-0410-b5e6-96231b3b80d8
so don't claim they are. They are allocated using DAG.getNode, so attempts
to access MemSDNode fields results in reading off the end of the allocated
memory. This fixes crashes with "llc -debug" due to debug code trying to
print MemSDNode fields for these barrier nodes (since the crashes are not
deterministic, use valgrind to see this). Add some nasty checking to try
to catch this kind of thing in the future.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119901 91177308-0d34-0410-b5e6-96231b3b80d8
DAGCombine from making an illegal transformation of bitcast of a scalar to a
vector into a scalar_to_vector.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119819 91177308-0d34-0410-b5e6-96231b3b80d8
if the extension types were not the same. The result was that if you
fed a select with sext and zext loads, as in the testcase, then it
would get turned into a zext (or sext) of the select, which is wrong
in the cases when it should have been an sext (resp. zext). Reported
and diagnosed by Sebastien Deldon.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119728 91177308-0d34-0410-b5e6-96231b3b80d8
memset; we may need it to decide between MOVAPS and MOVUPS
later. Adjust a test that was looking for wrong code.
PR 3866 / 8675131.
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easier to debug, and to avoid complications when the CFG changes
in the middle of the instruction selection process.
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catastrophic compilation time in the event of unreasonable LLVM
IR. Code quality is a separate issue--someone upstream needs to do a
better job of reducing to llvm.memcpy. If the situation can be reproduced with
any supported frontend, then it will be a separate bug.
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to perform the copy, which may be of lots of memory [*]. It would be good if the
fall-back code generated something reasonable, i.e. did the copy in a loop, rather
than vast numbers of loads and stores. Add a note about this. Currently target
specific code seems to always kick in so this is more of a theoretical issue rather
than a practical one now that X86 has been fixed.
[*] It's amazing how often people pass mega-byte long arrays by copy...
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with a SimpleValueType, while an EVT supports equality and
inequality comparisons with SimpleValueType.
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value type, so there is no point in passing it around using
an EVT. Use the simpler MVT everywhere. Rather than trying
to propagate this information maximally in all the code that
using the calling convention stuff, I chose to do a mainly
low impact change instead.
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1. Fix pre-ra scheduler so it doesn't try to push instructions above calls to
"optimize for latency". Call instructions don't have the right latency and
this is more likely to use introduce spills.
2. Fix if-converter cost function. For ARM, it should use instruction latencies,
not # of micro-ops since multi-latency instructions is completely executed
even when the predicate is false. Also, some instruction will be "slower"
when they are predicated due to the register def becoming implicit input.
rdar://8598427
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