summaryrefslogtreecommitdiffstats
path: root/llvm/lib/Analysis/ValueTracking.cpp
Commit message (Collapse)AuthorAgeFilesLines
...
* [ValueTracking] Calls to @llvm.assume always returnSanjoy Das2016-06-141-1/+2
| | | | | | | | | | | | This change teaches llvm::isGuaranteedToTransferExecutionToSuccessor that calls to @llvm.assume always terminate. Most other relevant intrinsics should be covered by the "CS.onlyReadsMemory() || CS.onlyAccessesArgMemory()" bit but we were missing @llvm.assumes because we state that it clobbers memory. Added an LICM test case, but this change is not specific to LICM. llvm-svn: 272703
* [LICM] Make isGuaranteedToExecute more accurate.Eli Friedman2016-06-111-13/+39
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: Make isGuaranteedToExecute use the isGuaranteedToTransferExecutionToSuccessor helper, and make that helper a bit more accurate. There's a potential performance impact here from assuming that arbitrary calls might not return. This probably has little impact on loads and stores to a pointer because most things alias analysis can reason about are dereferenceable anyway. The other impacts, like less aggressive hoisting of sdiv by a variable and less aggressive hoisting around volatile memory operations, are unlikely to matter for real code. This also impacts SCEV, which uses the same helper. It's a minor improvement there because we can tell that, for example, memcpy always returns normally. Strictly speaking, it's also introducing a bug, but it's not any worse than everywhere else we assume readonly functions terminate. Fixes http://llvm.org/PR27857. Reviewers: hfinkel, reames, chandlerc, sanjoy Subscribers: broune, llvm-commits Differential Revision: http://reviews.llvm.org/D21167 llvm-svn: 272489
* Teach isGuarantdToTransferExecToSuccessor about debug info intrinsicsSanjoy Das2016-06-081-3/+6
| | | | | | Calls to `@llvm.dbg.*` can be assumed to terminate. llvm-svn: 272180
* Avoid copies of std::strings and APInt/APFloats where we only read from itBenjamin Kramer2016-06-081-1/+1
| | | | | | | | As suggested by clang-tidy's performance-unnecessary-copy-initialization. This can easily hit lifetime issues, so I audited every change and ran the tests under asan, which came back clean. llvm-svn: 272126
* transform obscured FP sign bit ops into a fabs/fneg using TLI hookSanjay Patel2016-06-021-10/+2
| | | | | | | | | | | | | | | | | | | This is effectively a revert of: http://reviews.llvm.org/rL249702 - [InstCombine] transform masking off of an FP sign bit into a fabs() intrinsic call (PR24886) and: http://reviews.llvm.org/rL249701 - [ValueTracking] teach computeKnownBits that a fabs() clears sign bits and a reimplementation as a DAG combine for targets that have IEEE754-compliant fabs/fneg instructions. This is intended to resolve the objections raised on the dev list: http://lists.llvm.org/pipermail/llvm-dev/2016-April/098154.html and: https://llvm.org/bugs/show_bug.cgi?id=24886#c4 In the interest of patch minimalism, I've only partly enabled AArch64. PowerPC, MIPS, x86 and others can enable later. Differential Revision: http://reviews.llvm.org/D19391 llvm-svn: 271573
* [SCEV] See through op.with.overflow intrinsics (re-apply)Sanjoy Das2016-05-291-0/+61
| | | | | | | | | | | | | | | | | | | Summary: This change teaches SCEV to see reduce `(extractvalue 0 (op.with.overflow X Y))` into `op X Y` (with a no-wrap tag if possible). This was first checked in at r265912 but reverted in r265950 because it exposed some issues around how SCEV handled post-inc add recurrences. Those issues have now been fixed. Reviewers: atrick, regehr Subscribers: mcrosier, mzolotukhin, llvm-commits Differential Revision: http://reviews.llvm.org/D18684 llvm-svn: 271152
* [ValueTracking] ICmp instructions propagate poisonSanjoy Das2016-05-291-0/+5
| | | | | | | This is a stripped down version of D19211, leaving out the questionable "branching in poison is UB" bit. llvm-svn: 271150
* [ValueTracking, InstSimplify] extend isKnownNonZero() to handle vector constantsSanjay Patel2016-05-241-1/+14
| | | | | | | | | | | | | Similar in spirit to D20497 : If all elements of a constant vector are known non-zero, then we can say that the whole vector is known non-zero. It seems like we could extend this to FP scalar/vector too, but isKnownNonZero() says it only works for integers and pointers for now. Differential Revision: http://reviews.llvm.org/D20544 llvm-svn: 270562
* fix formatting; NFCSanjay Patel2016-05-231-4/+2
| | | | llvm-svn: 270465
* use 'auto' with 'dyn_cast'; fix formatting; NFCSanjay Patel2016-05-221-10/+8
| | | | llvm-svn: 270370
* [ValueTracking, InstCombine] extend isKnownToBeAPowerOfTwo() to handle ↵Sanjay Patel2016-05-221-3/+4
| | | | | | | | | | | | | | vector splat constants We could try harder to handle non-splat vector constants too, but that seems much rarer to me. Note that the div test isn't resolved because there's a check for isIntegerTy() guarding that transform. Differential Revision: http://reviews.llvm.org/D20497 llvm-svn: 270369
* [ValueTracking] Use guards to prove non-nullness of a valueSanjoy Das2016-05-101-9/+11
| | | | | | | | | | Reviewers: apilipenko, majnemer, reames Subscribers: mcrosier, llvm-commits Differential Revision: http://reviews.llvm.org/D20044 llvm-svn: 269008
* [ValueTracking] Hoist some computation out of a loop; NFCSanjoy Das2016-05-071-20/+11
| | | | | | There is no need to match the comparison instruction repeatedly. llvm-svn: 268836
* Clean up comment; NFCSanjoy Das2016-05-071-1/+1
| | | | llvm-svn: 268835
* Delete trailing whitespace; NFCSanjoy Das2016-05-071-8/+8
| | | | llvm-svn: 268834
* [ValueTracking] Early exit when further analysis won't be fruitful.Chad Rosier2016-05-051-15/+30
| | | | | | | This should have NFC in the context of codegen, but may have positive implications on compile-time. llvm-svn: 268651
* [ValueTracking] Improve isImpliedCondition for matching LHS and Imm RHSs.Chad Rosier2016-05-051-0/+29
| | | | llvm-svn: 268636
* [ConstantFolding, ValueTracking] Fold constants involving bitcasts of ↵David Majnemer2016-05-041-2/+21
| | | | | | | | | | | | | | | | | ConstantVector We assumed that ConstantVectors would be rather uninteresting from the perspective of analysis. However, this is not the case due to a quirk of how LLVM handles vectors of i1. Vectors of i1 are not ConstantDataVectors like vectors of i8, i16, i32 or i64 because i1's SizeInBits differs from it's StoreSizeInBytes. This leads to it being categorized as a ConstantVector instead of a ConstantDataVector. Instead, treat ConstantVector more uniformly. This fixes PR27591. llvm-svn: 268479
* [ValueTracking] Make the code in lookThroughCastDavid Majnemer2016-04-291-16/+9
| | | | | | No functionality change is intended. llvm-svn: 268108
* [InstCombine] Determine the result of a select based on a dominating condition.Chad Rosier2016-04-291-1/+4
| | | | | | Differential Revision: http://reviews.llvm.org/D19550 llvm-svn: 268104
* [ValueTracking] matchSelectPattern needs to be more careful around FPDavid Majnemer2016-04-291-19/+31
| | | | | | | | | | | | matchSelectPattern attempts to see through casts which mask min/max patterns from being more obvious. Under certain circumstances, it would misidentify a sequence of instructions as a min/max because it assumed that folding casts would preserve the result. This is not the case for floating point <-> integer casts. This fixes PR27575. llvm-svn: 268086
* [TLI] Unify LibFunc signature checking. NFCI.Ahmed Bougacha2016-04-271-60/+23
| | | | | | | | | I tried to be as close as possible to the strongest check that existed before; cleaning these up properly is left for future work. Differential Revision: http://reviews.llvm.org/D19469 llvm-svn: 267758
* [ValueTracking] Improve isImpliedCondition when the dominating cond is false.Chad Rosier2016-04-251-3/+6
| | | | llvm-svn: 267430
* Have isKnownNotFullPoison be smarter around control flowSanjoy Das2016-04-221-14/+32
| | | | | | | | | | | | | | | | | | | | | | | | | Summary: (... while still not using a PostDomTree) The way we use isKnownNotFullPoison from SCEV today, the new CFG walking logic will not trigger for any realistic cases -- it will kick in only for situations where we could have merged the contiguous basic blocks anyway[0], since the poison generating instruction dominates all of its non-PHI uses (which are the only uses we consider right now). However, having this change in place will allow a later bugfix to break fewer llvm-lit tests. [0]: i.e. cases where block A branches to block B and B is A's only successor and A is B's only predecessor. Reviewers: broune, bjarke.roune Subscribers: mcrosier, llvm-commits Differential Revision: http://reviews.llvm.org/D19212 llvm-svn: 267175
* Address Philip's post-commit feedback for r266987. NFC.Chad Rosier2016-04-211-2/+2
| | | | llvm-svn: 266998
* Refactor implied condition logic from ValueTracking directly into CmpInst. NFC.Chad Rosier2016-04-211-52/+2
| | | | | | Differential Revision: http://reviews.llvm.org/D19330 llvm-svn: 266987
* Add optimization for 'icmp slt (or A, B), A' and some related idioms based ↵Nick Lewycky2016-04-211-28/+8
| | | | | | | | | | | | | | | | | | | | on knowledge of the sign bit for A and B. No matter what value you OR in to A, the result of (or A, B) is going to be UGE A. When A and B are positive, it's SGE too. If A is negative, OR'ing a value into it can't make it positive, but can increase its value closer to -1, therefore (or A, B) is SGE A. Working through all possible combinations produces this truth table: ``` A is +, -, +/- F F F + B is T F ? - ? F ? +/- ``` The related optimizations are flipping the 'slt' for 'sge' which always NOTs the result (if the result is known), and swapping the LHS and RHS while swapping the comparison predicate. There are more idioms left to implement (aren't there always!) but I've stopped here because any more would risk becoming unreasonable for reviewers. llvm-svn: 266939
* [ValueTracking] Make isImpliedCondition return an Optional<bool>. NFC.Chad Rosier2016-04-201-61/+52
| | | | | | Phabricator Revision: http://reviews.llvm.org/D19277 llvm-svn: 266904
* [ValueTracking, VectorUtils] Refactor getIntrinsicIDForCallDavid Majnemer2016-04-191-2/+149
| | | | | | | | | | | | | The functionality contained within getIntrinsicIDForCall is two-fold: it checks if a CallInst's callee is a vectorizable intrinsic. If it isn't an intrinsic, it attempts to map the call's target to a suitable intrinsic. Move the mapping functionality into getIntrinsicForCallSite and rename getIntrinsicIDForCall to getVectorIntrinsicIDForCall while reimplementing it in terms of getIntrinsicForCallSite. llvm-svn: 266801
* [ValueTracking] Improve isImpliedCondition for conditions with matching ↵Chad Rosier2016-04-191-5/+99
| | | | | | | | | | | | | | | operands. This patch improves SimplifyCFG to catch cases like: if (a < b) { if (a > b) <- known to be false unreachable; } Phabricator Revision: http://reviews.llvm.org/D18905 llvm-svn: 266767
* Simplify strlen to a subtraction for certain cases.David L Kreitzer2016-04-131-13/+21
| | | | | | | | Patch by Li Huang (li1.huang@intel.com) Differential Revision: http://reviews.llvm.org/D18230 llvm-svn: 266200
* [InstCombine] We folded an fcmp to an i1 instead of a vector of i1David Majnemer2016-04-131-51/+50
| | | | | | | | | Remove an ad-hoc transform in InstCombine and replace it with more general machinery (ValueTracking, InstructionSimplify and VectorUtils). This fixes PR27332. llvm-svn: 266175
* This reverts commit r265913 and r265912Sanjoy Das2016-04-111-61/+0
| | | | | | | | | See PR27315 r265913: "[IndVars] Eliminate op.with.overflow when possible" r265912: "[SCEV] See through op.with.overflow intrinsics" llvm-svn: 265950
* [SCEV] See through op.with.overflow intrinsicsSanjoy Das2016-04-101-0/+61
| | | | | | | | | | | | | | | Summary: This change teaches SCEV to see reduce `(extractvalue 0 (op.with.overflow X Y))` into `op X Y` (with a no-wrap tag if possible). Reviewers: atrick, regehr Subscribers: mcrosier, mzolotukhin, llvm-commits Differential Revision: http://reviews.llvm.org/D18684 llvm-svn: 265912
* Don't IPO over functions that can be de-refinedSanjoy Das2016-04-081-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: Fixes PR26774. If you're aware of the issue, feel free to skip the "Motivation" section and jump directly to "This patch". Motivation: I define "refinement" as discarding behaviors from a program that the optimizer has license to discard. So transforming: ``` void f(unsigned x) { unsigned t = 5 / x; (void)t; } ``` to ``` void f(unsigned x) { } ``` is refinement, since the behavior went from "if x == 0 then undefined else nothing" to "nothing" (the optimizer has license to discard undefined behavior). Refinement is a fundamental aspect of many mid-level optimizations done by LLVM. For instance, transforming `x == (x + 1)` to `false` also involves refinement since the expression's value went from "if x is `undef` then { `true` or `false` } else { `false` }" to "`false`" (by definition, the optimizer has license to fold `undef` to any non-`undef` value). Unfortunately, refinement implies that the optimizer cannot assume that the implementation of a function it can see has all of the behavior an unoptimized or a differently optimized version of the same function can have. This is a problem for functions with comdat linkage, where a function can be replaced by an unoptimized or a differently optimized version of the same source level function. For instance, FunctionAttrs cannot assume a comdat function is actually `readnone` even if it does not have any loads or stores in it; since there may have been loads and stores in the "original function" that were refined out in the currently visible variant, and at the link step the linker may in fact choose an implementation with a load or a store. As an example, consider a function that does two atomic loads from the same memory location, and writes to memory only if the two values are not equal. The optimizer is allowed to refine this function by first CSE'ing the two loads, and the folding the comparision to always report that the two values are equal. Such a refined variant will look like it is `readonly`. However, the unoptimized version of the function can still write to memory (since the two loads //can// result in different values), and selecting the unoptimized version at link time will retroactively invalidate transforms we may have done under the assumption that the function does not write to memory. Note: this is not just a problem with atomics or with linking differently optimized object files. See PR26774 for more realistic examples that involved neither. This patch: This change introduces a new set of linkage types, predicated as `GlobalValue::mayBeDerefined` that returns true if the linkage type allows a function to be replaced by a differently optimized variant at link time. It then changes a set of IPO passes to bail out if they see such a function. Reviewers: chandlerc, hfinkel, dexonsmith, joker.eph, rnk Subscribers: mcrosier, llvm-commits Differential Revision: http://reviews.llvm.org/D18634 llvm-svn: 265762
* Mark some FP intrinsics as safe to speculatively executePeter Zotov2016-04-031-4/+16
| | | | | | | | | | | | | | | | | | Floating point intrinsics in LLVM are generally not speculatively executed, since most of them are defined to behave the same as libm functions, which set errno. However, the only error that can happen when executing ceil, floor, nearbyint, rint and round libm functions per POSIX.1-2001 is -ERANGE, and that requires the maximum value of the exponent to be smaller than the number of mantissa bits, which is not the case with any of the floating point types supported by LLVM. The trunc and copysign functions never set errno per per POSIX.1-2001. Differential Revision: http://reviews.llvm.org/D18643 llvm-svn: 265262
* [InstCombine] Fix incorrect rule from rL236202Sanjoy Das2016-03-311-1/+2
| | | | | | | The rule for SMIN introduced in rL236202 doesn't work as advertised: the check for Pred == ICmpInst::ICMP_SGT was missing. llvm-svn: 264996
* Delete trailing whitespaceSanjoy Das2016-03-311-1/+1
| | | | llvm-svn: 264995
* [ValueTracking] Extract isKnownPositive [NFCI]Philip Reames2016-03-091-0/+12
| | | | | | Extract out a generic interface from a recently landed patch and document a TODO in case compile time becomes a problem. llvm-svn: 263062
* [ValueTracking] "constant fold" an experimental hidden optionPhilip Reames2016-03-031-7/+0
| | | | llvm-svn: 262648
* [ValueTracking] Remove dead code from an old experimentPhilip Reames2016-03-031-208/+2
| | | | | | | | | | This experiment was originally about trying to use facts implied dominating conditions to infer more precise known bits. While the compile time was found to be acceptable on several large code bases, we never found sufficiently profitable examples to justify turning on the code by default. Given this, it's time to abandon the experiment. Several folks have commented that they've found this useful for experimentation, but nothing has come of those experiments. Given how easy the patch is to apply, there's no reason to leave the code in tree. For anyone interested in further investigation in this area, I recommend finding the summary email I sent on one of the original review threads. In particular, I now believe the use-list based approach is strictly worse than the dom-tree-walking approach. llvm-svn: 262646
* NFC. Move isDereferenceable to Loads.h/cppArtur Pilipenko2016-02-241-202/+1
| | | | | | | | | | This is a part of the refactoring to unify isSafeToLoadUnconditionally and isDereferenceablePointer functions. In subsequent change I'm going to eliminate isDerferenceableAndAlignedPointer from Loads API, leaving isSafeToLoadSpecualtively the only function to check is load instruction can be speculated. Reviewed By: hfinkel Differential Revision: http://reviews.llvm.org/D16180 llvm-svn: 261736
* NFC. Move getAlignment helper function from ValueTracking to Value class. Artur Pilipenko2016-02-241-42/+2
| | | | | | | | Reviewed By: reames, hfinkel Differential Revision: http://reviews.llvm.org/D16144 llvm-svn: 261735
* Remove uses of builtin comma operator.Richard Trieu2016-02-181-3/+6
| | | | | | Cleanup for upcoming Clang warning -Wcomma. No functionality change intended. llvm-svn: 261270
* [ValueTracking] Improve isKnownNonZero for PHI of non-zero constantsJun Bum Lim2016-02-011-0/+6
| | | | | | It is clear that a PHI is a non-zero if all incoming values are non-zero constants. llvm-svn: 259370
* ValueTracking: Use fixed array for assumption exclude set in Query.Matthias Braun2016-01-281-15/+27
| | | | | | | | | | | | The Query structure is constructed often and is relevant for compiletime performance. We can replace the SmallPtrSet for assumption exclusions in this structure with a fixed size array because we know the maximum number of elements. This improves typical clang -O3 -emit-llvm compiletime by 1.2% in my measurements. Differential Revision: http://reviews.llvm.org/D16204 llvm-svn: 259025
* [opaque pointer types] [NFC] GEP: replace get(Pointer)ElementType uses with ↵Eduard Burtescu2016-01-191-6/+4
| | | | | | | | | | | | | | | | | | get{Source,Result}ElementType. Summary: GEPOperator: provide getResultElementType alongside getSourceElementType. This is made possible by adding a result element type field to GetElementPtrConstantExpr, which GetElementPtrInst already has. GEP: replace get(Pointer)ElementType uses with get{Source,Result}ElementType. Reviewers: mjacob, dblaikie Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D16275 llvm-svn: 258145
* [opaque pointer types] Alloca: use getAllocatedType() instead of ↵Eduard Burtescu2016-01-181-1/+1
| | | | | | | | | | | | getType()->getPointerElementType(). Reviewers: mjacob Subscribers: llvm-commits, dblaikie Differential Revision: http://reviews.llvm.org/D16272 llvm-svn: 258028
* GlobalValue: use getValueType() instead of getType()->getPointerElementType().Manuel Jacob2016-01-161-1/+1
| | | | | | | | | | | | Reviewers: mjacob Subscribers: jholewinski, arsenm, dsanders, dblaikie Patch by Eduard Burtescu. Differential Revision: http://reviews.llvm.org/D16260 llvm-svn: 257999
* ValueTracking: Put DataLayout reference into the Query structure, NFC.Matthias Braun2016-01-151-257/+250
| | | | | | | | | It looks nicer and improves the compiletime of a typical clang -O3 -emit-llvm run by ~0.6% for me. Differential Revision: http://reviews.llvm.org/D16205 llvm-svn: 257944
OpenPOWER on IntegriCloud