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60 Commits

Author SHA1 Message Date
Hal Finkel 15aeaaf24a Add additional patterns for @llvm.assume in ValueTracking
This builds on r217342, which added the infrastructure to compute known bits
using assumptions (@llvm.assume calls). That original commit added only a few
patterns (to catch common cases related to determining pointer alignment); this
change adds several other patterns for simple cases.

r217342 contained that, for assume(v & b = a), bits in the mask
that are known to be one, we can propagate known bits from the a to v. It also
had a known-bits transfer for assume(a = b). This patch adds:

assume(~(v & b) = a) : For those bits in the mask that are known to be one, we
                       can propagate inverted known bits from the a to v.

assume(v | b = a) :    For those bits in b that are known to be zero, we can
                       propagate known bits from the a to v.

assume(~(v | b) = a):  For those bits in b that are known to be zero, we can
                       propagate inverted known bits from the a to v.

assume(v ^ b = a) :    For those bits in b that are known to be zero, we can
		       propagate known bits from the a to v. For those bits in
		       b that are known to be one, we can propagate inverted
                       known bits from the a to v.

assume(~(v ^ b) = a) : For those bits in b that are known to be zero, we can
		       propagate inverted known bits from the a to v. For those
		       bits in b that are known to be one, we can propagate
                       known bits from the a to v.

assume(v << c = a) :   For those bits in a that are known, we can propagate them
                       to known bits in v shifted to the right by c.

assume(~(v << c) = a) : For those bits in a that are known, we can propagate
                        them inverted to known bits in v shifted to the right by c.

assume(v >> c = a) :   For those bits in a that are known, we can propagate them
                       to known bits in v shifted to the right by c.

assume(~(v >> c) = a) : For those bits in a that are known, we can propagate
                        them inverted to known bits in v shifted to the right by c.

assume(v >=_s c) where c is non-negative: The sign bit of v is zero

assume(v >_s c) where c is at least -1: The sign bit of v is zero

assume(v <=_s c) where c is negative: The sign bit of v is one

assume(v <_s c) where c is non-positive: The sign bit of v is one

assume(v <=_u c): Transfer the known high zero bits

assume(v <_u c): Transfer the known high zero bits (if c is know to be a power
                 of 2, transfer one more)

A small addition to InstCombine was necessary for some of the test cases. The
problem is that when InstCombine was simplifying and, or, etc. it would fail to
check the 'do I know all of the bits' condition before checking less specific
conditions and would not fully constant-fold the result. I'm not sure how to
trigger this aside from using assumptions, so I've just included the change
here.

llvm-svn: 217343
2014-09-07 19:21:07 +00:00
Hal Finkel 60db05896a Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.)
This change, which allows @llvm.assume to be used from within computeKnownBits
(and other associated functions in ValueTracking), adds some (optional)
parameters to computeKnownBits and friends. These functions now (optionally)
take a "context" instruction pointer, an AssumptionTracker pointer, and also a
DomTree pointer, and most of the changes are just to pass this new information
when it is easily available from InstSimplify, InstCombine, etc.

As explained below, the significant conceptual change is that known properties
of a value might depend on the control-flow location of the use (because we
care that the @llvm.assume dominates the use because assumptions have
control-flow dependencies). This means that, when we ask if bits are known in a
value, we might get different answers for different uses.

The significant changes are all in ValueTracking. Two main changes: First, as
with the rest of the code, new parameters need to be passed around. To make
this easier, I grouped them into a structure, and I made internal static
versions of the relevant functions that take this structure as a parameter. The
new code does as you might expect, it looks for @llvm.assume calls that make
use of the value we're trying to learn something about (often indirectly),
attempts to pattern match that expression, and uses the result if successful.
By making use of the AssumptionTracker, the process of finding @llvm.assume
calls is not expensive.

Part of the structure being passed around inside ValueTracking is a set of
already-considered @llvm.assume calls. This is to prevent a query using, for
example, the assume(a == b), to recurse on itself. The context and DT params
are used to find applicable assumptions. An assumption needs to dominate the
context instruction, or come after it deterministically. In this latter case we
only handle the specific case where both the assumption and the context
instruction are in the same block, and we need to exclude assumptions from
being used to simplify their own ephemeral values (those which contribute only
to the assumption) because otherwise the assumption would prove its feeding
comparison trivial and would be removed.

This commit adds the plumbing and the logic for a simple masked-bit propagation
(just enough to write a regression test). Future commits add more patterns
(and, correspondingly, more regression tests).

llvm-svn: 217342
2014-09-07 18:57:58 +00:00
David Majnemer 49775e0173 InstCombine: Don't unconditionally preserve 'nuw' when shrinking constants
Consider:
  %add = add nuw i32 %a, -16777216
  %and = and i32 %add, 255

Regardless of whether or not we demand the sign bit of %add, we cannot
replace -16777216 with 2130706432 without also removing 'nuw' from the
instruction.

llvm-svn: 216273
2014-08-22 17:11:04 +00:00
David Majnemer 42b83a5e36 InstCombine: Don't unconditionally preserve 'nsw' when shrinking constants
Consider:
  %add = add nsw i32 %a, -16777216
  %and = and i32 %add, 255

Regardless of whether or not we demand the sign bit of %add, we cannot
replace -16777216 with 2130706432 without also removing 'nsw' from the
instruction.

This fixes PR20377.

llvm-svn: 216261
2014-08-22 07:56:32 +00:00
Jay Foad a0653a3e6c Rename ComputeMaskedBits to computeKnownBits. "Masked" has been
inappropriate since it lost its Mask parameter in r154011.

llvm-svn: 208811
2014-05-14 21:14:37 +00:00
Craig Topper e73658ddbb [C++] Use 'nullptr'.
llvm-svn: 207394
2014-04-28 04:05:08 +00:00
Craig Topper f40110f4d8 [C++] Use 'nullptr'. Transforms edition.
llvm-svn: 207196
2014-04-25 05:29:35 +00:00
Chandler Carruth 964daaaf19 [Modules] Fix potential ODR violations by sinking the DEBUG_TYPE
definition below all of the header #include lines, lib/Transforms/...
edition.

This one is tricky for two reasons. We again have a couple of passes
that define something else before the includes as well. I've sunk their
name macros with the DEBUG_TYPE.

Also, InstCombine contains headers that need DEBUG_TYPE, so now those
headers #define and #undef DEBUG_TYPE around their code, leaving them
well formed modular headers. Fixing these headers was a large motivation
for all of these changes, as "leaky" macros of this form are hard on the
modules implementation.

llvm-svn: 206844
2014-04-22 02:55:47 +00:00
Chandler Carruth 5f1f26e891 [Modules] Sink all the DEBUG_TYPE defines for InstCombine out of the
header files and into the cpp files.

These files will require more touches as the header files actually use
DEBUG(). Eventually, I'll have to introduce a matched #define and #undef
of DEBUG_TYPE for the header files, but that comes as step N of many to
clean all of this up.

llvm-svn: 206777
2014-04-21 19:51:41 +00:00
Chandler Carruth 820a908df7 [Modules] Move the LLVM IR pattern match header into the IR library, it
obviously is coupled to the IR.

llvm-svn: 202818
2014-03-04 11:08:18 +00:00
Rafael Espindola 37dc9e19f5 Rename many DataLayout variables from TD to DL.
I am really sorry for the noise, but the current state where some parts of the
code use TD (from the old name: TargetData) and other parts use DL makes it
hard to write a patch that changes where those variables come from and how
they are passed along.

llvm-svn: 201827
2014-02-21 00:06:31 +00:00
Craig Topper ef9e993eaa Remove x86_sse42_crc32_64_8 intrinsic. It has no functional difference from x86_sse42_crc32_32_8 and was not mapped to a clang builtin. I'm not even sure why this form of the instruction is even called out explicitly in the docs. Also add AutoUpgrade support to convert it into the other intrinsic with appropriate trunc and zext.
llvm-svn: 192672
2013-10-15 05:20:47 +00:00
Benjamin Kramer 010f108382 InstCombine: Check for zero shift amounts before subtracting one causing integer overflow.
PR17026. Also avoid undefined shifts and shift amounts larger than 64 bits
(those are always undef because we can't represent integer types that large).

llvm-svn: 189672
2013-08-30 14:35:35 +00:00
Benjamin Kramer 21b972ae94 InstCombine: Don't just copy known bits from the first operand of an srem.
That's obviously wrong. Conservatively restrict it to the sign bit, which
matches the original intention of this analysis. Fixes PR15940.

llvm-svn: 181518
2013-05-09 16:32:32 +00:00
Chandler Carruth 9fb823bbd4 Move all of the header files which are involved in modelling the LLVM IR
into their new header subdirectory: include/llvm/IR. This matches the
directory structure of lib, and begins to correct a long standing point
of file layout clutter in LLVM.

There are still more header files to move here, but I wanted to handle
them in separate commits to make tracking what files make sense at each
layer easier.

The only really questionable files here are the target intrinsic
tablegen files. But that's a battle I'd rather not fight today.

I've updated both CMake and Makefile build systems (I think, and my
tests think, but I may have missed something).

I've also re-sorted the includes throughout the project. I'll be
committing updates to Clang, DragonEgg, and Polly momentarily.

llvm-svn: 171366
2013-01-02 11:36:10 +00:00
Craig Topper 4c94775198 Remove trailing whitespace
llvm-svn: 170990
2012-12-22 18:09:02 +00:00
Shuxin Yang 81b3678564 - Fix a problematic way in creating all-the-1 APInt.
- Propagate "exact" bit of [l|a]shr instruction.

llvm-svn: 169942
2012-12-12 00:29:03 +00:00
Shuxin Yang 73285933c9 For rdar://12329730, last piece.
This change attempts to simplify (X^Y) -> X or Y in the user's context if we know that
only bits from X or Y are demanded.

  A minimized case is provided bellow. This change will simplify "t>>16" into "var1 >>16".

  =============================================================
  unsigned foo (unsigned val1, unsigned val2) {
    unsigned t = val1 ^ 1234;
    return (t >> 16) | t; // NOTE: t is used more than once.
  }
  =============================================================

  Note that if the "t" were used only once, the expression would be finally optimized as well.
However, with with this change, the optimization will take place earlier.

  Reviewed by Nadav, Thanks a lot!

llvm-svn: 169317
2012-12-04 22:15:32 +00:00
Shuxin Yang 86c0e232b7 rdar://12329730 (2nd part, revised)
The type of shirt-right (logical or arithemetic) should remain unchanged 
when transforming  "X << C1 >> C2" into "X << (C1-C2)"

llvm-svn: 169209
2012-12-04 03:28:32 +00:00
Shuxin Yang 63e999edbf rdar://12329730 (2nd part)
This change tries to simmplify E1 = " X >> C1 << C2" into :
  - E2 = "X << (C2 - C1)" if C2 > C1, or
  - E2 = "X >> (C1 - C2)" if C1 > C2, or
  - E2 = X if C1 == C2.

 Reviewed by Nadav. Thanks!

llvm-svn: 169182
2012-12-04 00:04:54 +00:00
Micah Villmow cdfe20b97f Move TargetData to DataLayout.
llvm-svn: 165402
2012-10-08 16:38:25 +00:00
Sylvestre Ledru 91ce36c986 Revert 'Fix a typo 'iff' => 'if''. iff is an abreviation of if and only if. See: http://en.wikipedia.org/wiki/If_and_only_if Commit 164767
llvm-svn: 164768
2012-09-27 10:14:43 +00:00
Sylvestre Ledru 721cffd53a Fix a typo 'iff' => 'if'
llvm-svn: 164767
2012-09-27 09:59:43 +00:00
Pete Cooper abc13af9c6 Simplify demanded bits of select sources where the condition is a constant vector
llvm-svn: 160835
2012-07-26 23:10:24 +00:00
Pete Cooper e807e45bff Teach SimplifyDemandedBits how to look through fpext and fptrunc to simplify their operand
llvm-svn: 160823
2012-07-26 22:37:04 +00:00
Evan Cheng e6a3b03ee0 Back out r160101 and instead implement a dag combine to recover from instcombine transformation.
llvm-svn: 160387
2012-07-17 18:54:11 +00:00
Evan Cheng 493eb32ff4 Instcombine was transforming:
%shr = lshr i64 %key, 3
  %0 = load i64* %val, align 8
  %sub = add i64 %0, -1
  %and = and i64 %sub, %shr
  ret i64 %and

to:
  %shr = lshr i64 %key, 3
  %0 = load i64* %val, align 8
  %sub = add i64 %0, 2305843009213693951
  %and = and i64 %sub, %shr
  ret i64 %and

The demanded bit optimization is actually a pessimization because add -1 would
be codegen'ed as a sub 1. Teach the demanded constant shrinking optimization
to check for negated constant to make sure it is actually reducing the width
of the constant.

rdar://11793464

llvm-svn: 160101
2012-07-12 01:45:35 +00:00
Rafael Espindola ba0a6cabb8 Always compute all the bits in ComputeMaskedBits.
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
2012-04-04 12:51:34 +00:00
Chris Lattner 0256be96f2 continue making the world safe for ConstantDataVector. At this point,
we should (theoretically optimize and codegen ConstantDataVector as well
as ConstantVector.

llvm-svn: 149116
2012-01-27 03:08:05 +00:00
Chris Lattner 6705883ad8 use Constant::getAggregateElement to simplify a bunch of code.
llvm-svn: 148934
2012-01-25 06:48:06 +00:00
Chris Lattner 47a86bdbe2 use ConstantVector::getSplat in a few places.
llvm-svn: 148929
2012-01-25 06:02:56 +00:00
Chris Lattner a0d01ff567 basic instcombine support for CDS.
llvm-svn: 148806
2012-01-24 14:31:22 +00:00
Nick Lewycky 0c48afa0ed Teach instcombine all sorts of great stuff about shifts that have exact, nuw or
nsw bits on them.

llvm-svn: 147528
2012-01-04 09:28:29 +00:00
Benjamin Kramer 010337c838 InstCombine: Canonicalize (2^n)-1 - x into (2^n)-1 ^ x iff x is known to be smaller than 2^n.
This has the obvious advantage of being commutable and is always a win on x86 because
const - x wastes a register there. On less weird architectures this may lead to
a regression because other arithmetic doesn't fuse with it anymore. I'll address that
problem in a followup.

llvm-svn: 147254
2011-12-24 17:31:38 +00:00
Benjamin Kramer 547b6c5ecd Stop emitting instructions with the name "tmp" they eat up memory and have to be uniqued, without any benefit.
If someone prefers %tmp42 to %42, run instnamer.

llvm-svn: 140634
2011-09-27 20:39:19 +00:00
Eli Friedman 888bea0b95 Make demanded-elt simplification for shufflevector slightly stronger. Spotted by inspection.
llvm-svn: 139768
2011-09-15 01:14:29 +00:00
Chris Lattner 229907cd11 land David Blaikie's patch to de-constify Type, with a few tweaks.
llvm-svn: 135375
2011-07-18 04:54:35 +00:00
Chad Rosier b362884ca9 Renamed llvm.x86.sse42.crc32 intrinsics; crc64 doesn't exist.
crc32.[8|16|32] have been renamed to .crc32.32.[8|16|32] and
crc64.[8|16|32] have been renamed to .crc32.64.[8|64].

llvm-svn: 132163
2011-05-26 23:13:19 +00:00
Evan Cheng e8d2e9eb35 Revert r131664 and fix it in instcombine instead. rdar://9467055
llvm-svn: 131708
2011-05-20 00:54:37 +00:00
Eli Friedman 6efb64ea8e Make the demanded bits/elements optimizations preserve debug line information.
I'm not sure this is quite ideal, but I can't really think of any better way to do it.

llvm-svn: 131616
2011-05-19 01:20:42 +00:00
Stuart Hastings 5bd18b6638 X86 pmovsx/pmovzx ignore the upper half of their inputs.
rdar://problem/6945110

llvm-svn: 131493
2011-05-17 22:13:31 +00:00
Eli Friedman a81a82dcaf PR9346: Prevent SimplifyDemandedBits from incorrectly introducing
INT_MIN % -1.

llvm-svn: 127306
2011-03-09 01:28:35 +00:00
Nick Lewycky e467979d0a Add more analysis of the sign bit of an srem instruction. If the LHS is negative
then the result could go either way. If it's provably positive then so is the
srem. Fixes PR9343 #7!

llvm-svn: 127146
2011-03-07 01:50:10 +00:00
Chris Lattner 768003c59e teach SimplifyDemandedBits that exact shifts demand the bits they
are shifting out since they do require them to be zeros.  Similarly
for NUW/NSW bits of shl

llvm-svn: 125263
2011-02-10 05:09:34 +00:00
Jay Foad 583abbc4df PR5207: Change APInt methods trunc(), sext(), zext(), sextOrTrunc() and
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
2010-12-07 08:25:19 +00:00
Jay Foad 25a5e4ca1f PR5207: Rename overloaded APInt methods set(), clear(), flip() to
setAllBits(), setBit(unsigned), etc.

llvm-svn: 120564
2010-12-01 08:53:58 +00:00
Gabor Greif e23efeef10 use ArgOperand API
llvm-svn: 107016
2010-06-28 16:45:00 +00:00
Gabor Greif 7943017490 use ArgOperand API
llvm-svn: 106737
2010-06-24 12:35:13 +00:00
Eric Christopher 7258dcd77f Revert 101465, it broke internal OpenGL testing.
Probably the best way to know that all getOperand() calls have been handled
is to replace that API instead of updating.

llvm-svn: 101579
2010-04-16 23:37:20 +00:00
Gabor Greif f375520f7b reapply r101434
with a fix for self-hosting

rotate CallInst operands, i.e. move callee to the back
of the operand array

the motivation for this patch are laid out in my mail to llvm-commits:
more efficient access to operands and callee, faster callgraph-construction,
smaller compiler binary

llvm-svn: 101465
2010-04-16 15:33:14 +00:00