Stop custom lowering forr x86 DEC64m from happening if the load in the lowered sequence has more than 1 user

llvm-svn: 150537

If the DEC node had more than one user, it was doing this lowering but
leaving the original DEC node around and so decrementing twice.

Fixes PR11964.

llvm-svn: 150356

llvm-svn: 148578

same pattern. We already had this pattern is a few places, but others
tried to make a rough approximation of an actual DAG structure. As not
everywhere went to this trouble, nothing could rely on this being done.
In fact, I've checked all references to these node Ids, and the ones
that are using the topo-sort properties are actually satisfied with
a strict-weak-ordering. The requirement appears to be that Use >= Def.

I've added a big blurb of comments to this bit of the transform to
clarify why the order is so important for the next reader of the code.

I'm starting with this change as it is very small, and trivially
reverted if something breaks or the >= above really does need to be >.
If that proves the case, we can hide the problem by reverting this
patch, but the problem exists elsewhere as well, and so a more
comprehensive solution will be needed.

llvm-svn: 148001

hoped this would revive one of the llvm-gcc selfhost build bots, but it
didn't so it doesn't appear that my transform is the culprit.

If anyone else is seeing failures, please let me know!

llvm-svn: 147957

strange build bot failures that look like a miscompile into an infloop.
I'll investigate this tomorrow, but I'd both like to know whether my
patch is the culprit, and get the bots back to green.

llvm-svn: 147945

lots of lines of code. No functionality changed.

llvm-svn: 147942

SRL-rooted code.

llvm-svn: 147941

factor the differences that were hiding in one of them into its other
caller, the SRL handling code. No change in behavior.

llvm-svn: 147940

mask+shift pairs at the beginning of the ISD::AND case block, and then
hoist the final pattern into a helper function, simplifying and
reflowing it appropriately. This should have no observable behavior
change, but several simplifications fell out of this such as directly
computing the new mask constant, etc.

llvm-svn: 147939

extracts and scaled addressing modes into its own helper function. No
functionality changed here, just hoisting and layout fixes falling out
of that hoisting.

llvm-svn: 147937

detect a pattern which can be implemented with a small 'shl' embedded in
the addressing mode scale. This happens in real code as follows:

  unsigned x = my_accelerator_table[input >> 11];

Here we have some lookup table that we look into using the high bits of
'input'. Each entity in the table is 4-bytes, which means this
implicitly gets turned into (once lowered out of a GEP):

  *(unsigned*)((char*)my_accelerator_table + ((input >> 11) << 2));

The shift right followed by a shift left is canonicalized to a smaller
shift right and masking off the low bits. That hides the shift right
which x86 has an addressing mode designed to support. We now detect
masks of this form, and produce the longer shift right followed by the
proper addressing mode. In addition to saving a (rather large)
instruction, this also reduces stalls in Intel chips on benchmarks I've
measured.

In order for all of this to work, one part of the DAG needs to be
canonicalized *still further* than it currently is. This involves
removing pointless 'trunc' nodes between a zextload and a zext. Without
that, we end up generating spurious masks and hiding the pattern.

llvm-svn: 147936

this substraction will result in small negative numbers at worst which
become very large positive numbers on assignment and are thus caught by
the <=4 check on the next line. The >0 check clearly intended to catch
these as negative numbers.

Spotted by inspection, and impossible to trigger given the shift widths
that can be used.

llvm-svn: 147773

llvm-svn: 144811

by later instructions.

Only done for DEC64m right now.

Fixes <rdar://problem/6172640>

llvm-svn: 144705

across calls, and only check for nested dependences on the special
call-sequence-resource register.

llvm-svn: 143660

llvm-svn: 143262

fixes: Use a separate register, instead of SP, as the
calling-convention resource, to avoid spurious conflicts with
actual uses of SP. Also, fix unscheduling of calling sequences,
which can be triggered by pseudo-two-address dependencies.

llvm-svn: 143206

it fixes the dragonegg self-host (it looks like gcc is miscompiled).
Original commit messages:
Eliminate LegalizeOps' LegalizedNodes map and have it just call RAUW
on every node as it legalizes them. This makes it easier to use
hasOneUse() heuristics, since unneeded nodes can be removed from the
DAG earlier.

Make LegalizeOps visit the DAG in an operands-last order. It previously
used operands-first, because LegalizeTypes has to go operands-first, and
LegalizeTypes used to be part of LegalizeOps, but they're now split.
The operands-last order is more natural for several legalization tasks.
For example, it allows lowering code for nodes with floating-point or
vector constants to see those constants directly instead of seeing the
lowered form (often constant-pool loads). This makes some things
somewhat more complicated today, though it ought to allow things to be
simpler in the future. It also fixes some bugs exposed by Legalizing
using RAUW aggressively.

Remove the part of LegalizeOps that attempted to patch up invalid chain
operands on libcalls generated by LegalizeTypes, since it doesn't work
with the new LegalizeOps traversal order. Instead, define what
LegalizeTypes is doing to be correct, and transfer the responsibility
of keeping calls from having overlapping calling sequences into the
scheduler.

Teach the scheduler to model callseq_begin/end pairs as having a
physical register definition/use to prevent calls from having
overlapping calling sequences. This is also somewhat complicated, though
there are ways it might be simplified in the future.

This addresses rdar://9816668, rdar://10043614, rdar://8434668, and others.
Please direct high-level questions about this patch to management.

Delete #if 0 code accidentally left in.

llvm-svn: 143188

on every node as it legalizes them. This makes it easier to use
hasOneUse() heuristics, since unneeded nodes can be removed from the
DAG earlier.

Make LegalizeOps visit the DAG in an operands-last order. It previously
used operands-first, because LegalizeTypes has to go operands-first, and
LegalizeTypes used to be part of LegalizeOps, but they're now split.
The operands-last order is more natural for several legalization tasks.
For example, it allows lowering code for nodes with floating-point or
vector constants to see those constants directly instead of seeing the
lowered form (often constant-pool loads). This makes some things
somewhat more complicated today, though it ought to allow things to be
simpler in the future. It also fixes some bugs exposed by Legalizing
using RAUW aggressively.

Remove the part of LegalizeOps that attempted to patch up invalid chain
operands on libcalls generated by LegalizeTypes, since it doesn't work
with the new LegalizeOps traversal order. Instead, define what
LegalizeTypes is doing to be correct, and transfer the responsibility
of keeping calls from having overlapping calling sequences into the
scheduler.

Teach the scheduler to model callseq_begin/end pairs as having a
physical register definition/use to prevent calls from having
overlapping calling sequences. This is also somewhat complicated, though
there are ways it might be simplified in the future.

This addresses rdar://9816668, rdar://10043614, rdar://8434668, and others.
Please direct high-level questions about this patch to management.

llvm-svn: 143177

In 64-bit mode, sub_8bit_hi sub-registers can only be used by NOREX
instructions. The COPY created from the EXTRACT_SUBREG DAG node cannot
target all GR8 registers, only those in GR8_NOREX.

TO enforce this, we ensure that all instructions using the
EXTRACT_SUBREG are GR8_NOREX constrained.

This fixes PR11088.

llvm-svn: 141499

llvm-svn: 136653

Make sure we don't combine a large displacement and a frame index in the same addressing mode on x86-64.  It can overflow, leading to a crash/miscompile.

<rdar://problem/9763308>

llvm-svn: 135084

Refactor out checking for displacements on x86-64 addressing modes.  No functionality change.  Refactoring in preparation for an additional safety check in FoldOffsetIntoAddress.

Part of <rdar://problem/9763308>.

llvm-svn: 135079

up the valid constant check earlier.

rdar://9692967

llvm-svn: 134286

we didn't have an opcode for 64-bit constant or expressions.

Fixes rdar://9692967

llvm-svn: 134121

rdar://problem/8614450

llvm-svn: 131746

llvm-svn: 131459

Finishes off rdar://8470697

llvm-svn: 131458

llvm-svn: 131457

llvm-svn: 131456

Part of rdar://8470697

llvm-svn: 131200

Next up: xor and and.

Part of rdar://8470697

llvm-svn: 131171

llvm-svn: 130053

X86: Try to use a smaller encoding by transforming (X << C1) & C2 into (X & (C2 >> C1)) & C1. (Part of PR5039)

This tends to happen a lot with bitfield code generated by clang. A simple example for x86_64 is
uint64_t foo(uint64_t x) { return (x&1) << 42; }
which used to compile into bloated code:
	shlq	$42, %rdi               ## encoding: [0x48,0xc1,0xe7,0x2a]
	movabsq	$4398046511104, %rax    ## encoding: [0x48,0xb8,0x00,0x00,0x00,0x00,0x00,0x04,0x00,0x00]
	andq	%rdi, %rax              ## encoding: [0x48,0x21,0xf8]
	ret                             ## encoding: [0xc3]

with this patch we can fold the immediate into the and:
	andq	$1, %rdi                ## encoding: [0x48,0x83,0xe7,0x01]
	movq	%rdi, %rax              ## encoding: [0x48,0x89,0xf8]
	shlq	$42, %rax               ## encoding: [0x48,0xc1,0xe0,0x2a]
	ret                             ## encoding: [0xc3]

It's possible to save another byte by using 'andl' instead of 'andq' but I currently see no way of doing
that without making this code even more complicated. See the TODOs in the code.

llvm-svn: 129990

other getNode() methods.  Radar 9002173.

llvm-svn: 125665

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.

llvm-svn: 125470

CALL64 marks %xmm* as dead.

llvm-svn: 124354

into and/shift would cause nodes to move around and a dangling pointer
to happen.  The code tried to avoid this with a HandleSDNode, but 
got the details wrong.

llvm-svn: 123578

declaration and its assignments.

Found by clang static analyzer.

llvm-svn: 123486