summaryrefslogtreecommitdiffstats
path: root/llvm/test/Transforms
Commit message (Collapse)AuthorAgeFilesLines
* [EH] Keep filter clauses for types that have been caught.Andrew Kaylor2015-11-171-4/+7
| | | | | | | | The instruction combiner previously removed types from filter clauses in Landing Pad instructions if the type had previously been seen in a catch clause. This is incorrect and prevents unexpected exception handlers from rethrowing the caught type. Differential Revision: http://reviews.llvm.org/D14669 llvm-svn: 253370
* Vector of pointers in function attributes calculationElena Demikhovsky2015-11-171-0/+38
| | | | | | | | | While setting function attributes we check all instructions that may access memory. For a call instruction we check all arguments. The special check is required for pointers. I added vector-of-pointers to the call arguments types that should be checked. Differential Revision: http://reviews.llvm.org/D14693 llvm-svn: 253363
* [PRE] Preserve !invariant.load metadataPhilip Reames2015-11-171-0/+17
| | | | | | Spoted via inspection. Test case included. llvm-svn: 253275
* Add intermediate subtract instructions to reassociation worklist.Owen Anderson2015-11-168-17/+48
| | | | | | | | | | We sometimes create intermediate subtract instructions during reassociation. Adding these to the worklist to revisit exposes many additional reassociation opportunities. Patch by Aditya Nandakumar. llvm-svn: 253240
* [LoopStrengthReduce] Don't increment iterator past the end of the BBDavid Majnemer2015-11-161-0/+51
| | | | | | | | | | | We tried to move the insertion point beyond instructions like landingpad and cleanuppad. However, we *also* tried to move past catchpad. This is problematic because catchpad is also a terminator. This fixes PR25541. llvm-svn: 253238
* Don't generate discriminators for calls to debug intrinsicsPavel Labath2015-11-161-0/+30
| | | | | | | | | | | | | | Summary: This fails a check in Verifier.cpp, which checks for location matches between the declared variable and the !dbg attachments. Reviewers: dnovillo, dblaikie, danielcdh Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D14657 llvm-svn: 253194
* [Sink] Don't move landingpadsKeno Fischer2015-11-161-0/+33
| | | | | | | | | | | | | | | Summary: Moving landingpads into successor basic blocks makes the verifier sad. Teach Sink that much like PHI nodes and terminator instructions, landingpads (and cleanuppads, etc.) may not be moved between basic blocks. Reviewers: majnemer Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D14475 llvm-svn: 253182
* [GlobalOpt] Demote globals to locals more aggressivelyJames Molloy2015-11-153-2/+82
| | | | | | | | | | | | | | | | Global to local demotion can speed up programs that use globals a lot. It is particularly useful with LTO, when the entire call graph is known and most functions have been internalized. For a global to be demoted, it must only be accessed by one function and that function: 1. Must never recurse directly or indirectly, else the GV would be clobbered. 2. Must never rely on the value in GV at the start of the function (apart from the initializer). GlobalOpt can already do this, but it is hamstrung and only ever tries to demote globals inside "main", because C++ gives extra guarantees about how main is called - once and only once. In LTO mode, we can often prove the first property (if the function is internal by this point, we know enough about the callgraph to determine if it could possibly recurse). FunctionAttrs now infers the "norecurse" attribute for this reason. The second property can be proven for a subset of functions by proving that all loads from GV are dominated by a store to GV. This is conservative in the name of compile time - this only requires a DominatorTree which is fairly cheap in the grand scheme of things. We could do more fancy stuff with MemoryDependenceAnalysis too to catch more cases but this appears to catch most of the useful ones in my testing. llvm-svn: 253168
* Fixed GEP visitor in the InstCombine pass.Elena Demikhovsky2015-11-151-0/+23
| | | | | | | | | | | | | The current implementation of GEP visitor in InstCombine fails with assertion on Vector GEP with mix of scalar and vector types, like this: getelementptr double, double* %a, <8 x i32> %i (It fails to create a "sext" from <8 x i32> to <8 x i64>) I fixed it and added some tests. Differential Revision: http://reviews.llvm.org/D14485 llvm-svn: 253162
* Don't recompute LCSSA after loop-unrolling when possible.Michael Zolotukhin2015-11-141-0/+119
| | | | | | | | | | | | | | | | | | | | | | | | | Summary: Currently we always recompute LCSSA for outer loops after unrolling an inner loop. That leads to compile time problem when we have big loop nests, and we can solve it by avoiding unnecessary work. For instance, if w eonly do partial unrolling, we don't break LCSSA, so we don't need to rebuild it. Also, if all exits from the inner loop are inside the enclosing loop, then complete unrolling won't break LCSSA either. I replaced unconditional LCSSA recomputation with conditional recomputation + unconditional assert and added several tests, which were failing when I experimented with it. Soon I plan to follow up with a similar patch for recalculation of dominators tree. Reviewers: hfinkel, dexonsmith, bogner, joker.eph, chandlerc Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D14526 llvm-svn: 253126
* [LIR] Add support for creating memcpys from loops with a negative stride.Chad Rosier2015-11-131-2/+29
| | | | | | | | | | | | | | | This allows us to transform the below loop into a memcpy. void test(unsigned *__restrict__ a, unsigned *__restrict__ b) { for (int i = 2047; i >= 0; --i) { a[i] = b[i]; } } This is the memcpy version of r251518, which added support for memset with negative strided loops. llvm-svn: 253091
* [safestack] Rewrite isAllocaSafe using SCEV.Evgeniy Stepanov2015-11-134-4/+264
| | | | | | | | | | | | | | | Use ScalarEvolution to calculate memory access bounds. Handle function calls based on readnone/nocapture attributes. Handle memory intrinsics with constant size. This change improves both recall and precision of IsAllocaSafe. See the new tests (ex. BitCastWide) for the kind of code that was wrongly classified as safe. SCEV efficiency seems to be limited by the fact the SafeStack runs late (in CodeGenPrepare), and many loops are unrolled or otherwise not in LCSSA. llvm-svn: 253083
* [llvm-profdata] Add check for text profile formats and improve error ↵Nathan Slingerland2015-11-131-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | reporting (2nd try) Summary: This change addresses two possible instances of user error / confusion when merging sampled profile data. Previously any input that didn't match the raw or processed instrumented format would automatically be interpreted as instrumented profile text format data. No error would be reported during the merge. Example: If foo-sampled.profdata and bar-sampled.profdata are binary sampled profiles: Old behavior: $ llvm-profdata merge foo-sampled.profdata bar-sampled.profdata -output foobar-sampled.profdata $ llvm-profdata show -sample foobar-sampled.profdata error: foobar-sampled.profdata:1: Expected 'mangled_name:NUM:NUM', found lprofi This change adds basic checks for valid input data when assuming text input. It also makes error messages related to file format validity more specific about the assumbed profile data type. New behavior: $ llvm-profdata merge foo-sampled.profdata bar-sampled.profdata -o foobar-sampled.profdata error: foo.profdata: Unrecognized instrumentation profile encoding format Perhaps you forgot to use the -sample option? Reviewers: bogner, davidxl, dnovillo Subscribers: davidxl, llvm-commits Differential Revision: http://reviews.llvm.org/D14558 llvm-svn: 253009
* Revert "Fix bug 25440: GVN assertion after coercing loads"Tobias Grosser2015-11-121-66/+0
| | | | | | This reverts 252919 which broke LNT: MultiSource/Applications/SPASS llvm-svn: 252936
* Fix bug 25440: GVN assertion after coercing loadsWeiming Zhao2015-11-121-0/+66
| | | | | | | | | | | | | | | | Summary: when coercing loads, it inserts some instructions, which have no GV assigned. https://llvm.org/bugs/show_bug.cgi?id=25440 Reviewers: hfinkel, dberlin Subscribers: dberlin, llvm-commits Differential Revision: http://reviews.llvm.org/D14479 llvm-svn: 252919
* [InstCombine] Add trivial folding (bitreverse (bitreverse x)) -> xJames Molloy2015-11-121-0/+11
| | | | | | There are plenty more instcombines we could probably do with bitreverse, but this seems like a very obvious and trivial starting point and was brought up by Hal in his review. llvm-svn: 252879
* Revert "Revert "[FunctionAttrs] Identify norecurse functions""James Molloy2015-11-125-7/+69
| | | | | | This reapplies this patch, with test fixes. llvm-svn: 252871
* Revert "[FunctionAttrs] Identify norecurse functions"James Molloy2015-11-125-69/+7
| | | | | | This reverts commit r252862. This introduced test failures and I'm reverting while I investigate how this happened. llvm-svn: 252863
* [FunctionAttrs] Identify norecurse functionsJames Molloy2015-11-125-7/+69
| | | | | | | | | | | | | A function can be marked as norecurse if: * The SCC to which it belongs has cardinality 1; and either a) It does not call any non-norecurse function. This includes self-recursion; or b) It only has one callsite and the function that callsite is within is marked norecurse. a) is best propagated bottom-up and b) is best propagated top-down. We build up the norecurse attributes bottom-up using the existing SCC pass, and mark functions with no obvious recursion (but not provably norecurse) to sweep later, top-down. llvm-svn: 252862
* SamplePGO - Fix PR 25482 - Do not rely on llvm.dbg.cu for discriminatorsDiego Novillo2015-11-116-5/+29
| | | | | | | | | | | | | | | The discriminators pass relied on the presence of llvm.dbg.cu to decide whether to add discriminators, but this fails in the case where debug info is only enabled partially when -fprofile-sample-use is active. The reason llvm.dbg.cu is not present in these cases is to prevent codegen from emitting debug info (as it is only used for the sample profile pass). This changes the discriminators pass to also emit discriminators even when debug info is not being emitted. llvm-svn: 252763
* [MIPS] add overrides for isCheapToSpeculateCttz() and isCheapToSpeculateCtlz()Sanjay Patel2015-11-112-0/+48
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | MIPS32 has instructions for efficient count-leading/trailing-zeros, so this should be considered a cheap operation (and therefore fair game for speculation) for any MIPS32 implementation. The net result of allowing this speculation for the regression tests in this patch is that we get this code: ctlz: jr $ra clz $2, $4 cttz: addiu $1, $4, -1 not $2, $4 and $1, $2, $1 clz $1, $1 addiu $2, $zero, 32 jr $ra subu $2, $2, $1 Instead of: ctlz: beqz $4, $BB0_2 addiu $2, $zero, 32 clz $2, $4 $BB0_2: jr $ra nop cttz: beqz $4, $BB1_2 addiu $2, $zero, 32 addiu $1, $4, -1 not $2, $4 and $1, $2, $1 clz $1, $1 addiu $2, $zero, 32 subu $2, $2, $1 $BB1_2: jr $ra nop See D14469 for the larger motivation. Differential Revision: http://reviews.llvm.org/D14500 llvm-svn: 252755
* Sort the enums in Attributes.h in case insensitive alphabetical order.Akira Hatanaka2015-11-113-3/+3
| | | | | | | | | Sort the enums in preparation for moving the attributes to a table-gen file. rdar://problem/19836465 llvm-svn: 252692
* [ValueTracking] Teach isImpliedCondition a new bitwise trickSanjoy Das2015-11-101-0/+78
| | | | | | | | | | | | | | | | | | | Summary: This change teaches isImpliedCondition to prove things like (A | 15) < L ==> (A | 14) < L if the low 4 bits of A are known to be zero. Depends on D14391 Reviewers: majnemer, reames, hfinkel Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D14392 llvm-svn: 252673
* [PowerPC] Add an MI SSA peephole pass.Bill Schmidt2015-11-101-0/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch adds a pass for doing PowerPC peephole optimizations at the MI level while the code is still in SSA form. This allows for easy modifications to the instructions while depending on a subsequent pass of DCE. Both passes are very fast due to the characteristics of SSA. At this time, the only peepholes added are for cleaning up various redundancies involving the XXPERMDI instruction. However, I would expect this will be a useful place to add more peepholes for inefficiencies generated during instruction selection. The pass is placed after VSX swap optimization, as it is best to let that pass remove unnecessary swaps before performing any remaining clean-ups. The utility of these clean-ups are demonstrated by changes to four existing test cases, all of which now have tighter expected code generation. I've also added Eric Schweiz's bugpoint-reduced test from PR25157, for which we now generate tight code. One other test started failing for me, and I've fixed it (test/Transforms/PlaceSafepoints/finite-loops.ll) as well; this is not related to my changes, and I'm not sure why it works before and not after. The problem is that the CHECK-NOT: of "statepoint" from test1 fails because of the "statepoint" in test2, and so forth. Adding a CHECK-LABEL in between keeps the different occurrences of that string properly scoped. llvm-svn: 252651
* [ARM] add overrides for isCheapToSpeculateCttz() and isCheapToSpeculateCtlz()Sanjay Patel2015-11-102-0/+48
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ARM V6T2 has instructions for efficient count-leading/trailing-zeros, so this should be considered a cheap operation (and therefore fair game for speculation) for any ARM V6T2 implementation. The net result of allowing this speculation for the regression tests in this patch is that we get this code: ctlz: clz r0, r0 bx lr cttz: rbit r0, r0 clz r0, r0 bx lr Instead of: ctlz: cmp r0, #0 moveq r0, #32 clzne r0, r0 bx lr cttz: cmp r0, #0 moveq r0, #32 rbitne r0, r0 clzne r0, r0 bx lr This will help solve a general speculation/despeculation problem noted in PR24818: https://llvm.org/bugs/show_bug.cgi?id=24818 Differential Revision: http://reviews.llvm.org/D14469 llvm-svn: 252639
* [ValueTracking] Recognize that and(x, add (x, -1)) clears the low bitPhilip Reames2015-11-101-0/+65
| | | | | | | | | | This is a cleaned up version of a patch by John Regehr with permission. Originally found via the souper tool. If we add an odd number to x, then bitwise-and the result with x, we know that the low bit of the result must be zero. Either it was zero in x originally, or the add cleared it in the temporary value. As a result, one of the two values anded together must have the bit cleared. Differential Revision: http://reviews.llvm.org/D14315 llvm-svn: 252629
* [AArch64] add overrides for isCheapToSpeculateCttz() and ↵Sanjay Patel2015-11-101-0/+43
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | isCheapToSpeculateCtlz() AArch64 has instructions for efficient count-leading/trailing-zeros, so this should be considered a cheap operation (and therefore fair game for speculation) for any AArch64 implementation. The net result of allowing this speculation for the regression tests in this patch is that we get this code: ctlz: clz w0, w0 ret cttz: rbit w8, w0 clz w0, w8 ret Instead of: ctlz: cbz w0, .LBB0_2 clz w0, w0 ret .LBB0_2: orr w0, wzr, #0x20 ret cttz: cbz w0, .LBB1_2 rbit w8, w0 clz w0, w8 ret .LBB1_2: orr w0, wzr, #0x20 ret See D14469 for the larger motivation. Differential Revision: http://reviews.llvm.org/D14505 llvm-svn: 252625
* Revert "Strip metadata when speculatively hoisting instructions"Renato Golin2015-11-102-70/+0
| | | | | | | This reverts commit r252604, as it broke all ARM and AArch64 buildbots, as well as some x86, et al. llvm-svn: 252623
* Strip metadata when speculatively hoisting instructionsIgor Laevsky2015-11-102-0/+70
| | | | | | | | | | | | | | | | This is fix for PR24059. When we are hoisting instruction above some condition it may turn out that metadata on this instruction was control dependant on the condition. This metadata becomes invalid and we need to drop it. This patch should cover most obvious places of speculative execution (which I have found by greping isSafeToSpeculativelyExecute). I think there are more cases but at least this change covers the severe ones. Differential Revision: http://reviews.llvm.org/D14398 llvm-svn: 252604
* Inliner: Do zero-cost inlines even if above a negative threshold (PR24851)Hans Wennborg2015-11-101-0/+17
| | | | | | Differential Revision: http://reviews.llvm.org/D14499 llvm-svn: 252595
* Add discriminators for call instructions that are from the same line and ↵Dehao Chen2015-11-091-0/+48
| | | | | | | | | | | | | | same basic block. Summary: Call instructions that are from the same line and same basic block needs to have separate discriminators to distinguish between different callsites. Reviewers: davidxl, dnovillo, dblaikie Subscribers: dblaikie, probinson, llvm-commits Differential Revision: http://reviews.llvm.org/D14464 llvm-svn: 252492
* GlobalOpt should maintain externally_initialized when splitting aggregatesOliver Stannard2015-11-091-0/+50
| | | | | | | | | | | | | When GlobalOpt splits an internal, global variable with an aggregate type, it should propagate the externally_initialized flag to the newly created globals. This makes the pass safe for our downstream use of this flag, while still allowing some useful optimisations (such as removing dead parts of the split aggregate) to be performed. Differential Revision: http://reviews.llvm.org/D13382 llvm-svn: 252490
* [LoopVectorize] Address post-commit feedback on r250032James Molloy2015-11-091-1/+1
| | | | | | | | | | Implemented as many of Michael's suggestions as were possible: * clang-format the added code while it is still fresh. * tried to change Value* to Instruction* in many places in computeMinimumValueSizes - unfortunately there are several places where Constants need to be handled so this wasn't possible. * Reduce the pass list on loop-vectorization-factors.ll. * Fix a bug where we were querying MinBWs for I->getOperand(0) but using MinBWs[I]. llvm-svn: 252469
* Allow LLE/LD and the loop versioning infrastructure to use SCEV predicatesSilviu Baranga2015-11-093-3/+3
| | | | | | | | | | | | | | | | | | | Summary: LAA currently generates a set of SCEV predicates that must be checked by users. In the case of Loop Distribute/Loop Load Elimination, no such predicates could have been emitted, since we don't allow stride versioning. However, in the future there could be SCEV predicates that will need to be checked. This change adds support for SCEV predicate versioning in the Loop Distribute, Loop Load Eliminate and the loop versioning infrastructure. Reviewers: anemet Subscribers: mssimpso, sanjoy, llvm-commits Differential Revision: http://reviews.llvm.org/D14240 llvm-svn: 252467
* [LoopStrengthReduce] Don't bother fixing up PHIs from EH Pad predsDavid Majnemer2015-11-081-0/+53
| | | | | | | | We cannot really insert fixup code into a PHI's predecessor. This fixes PR25445. llvm-svn: 252416
* [FunctionAttrs] Fix an iterator wraparound bugSanjoy Das2015-11-071-0/+30
| | | | | | | | | | | | | | | | | | | Summary: This change fixes an iterator wraparound bug in `determinePointerReadAttrs`. Ideally, ++'ing off the `end()` of an iplist should result in a failed assert, but currently iplist seems to silently wrap to the head of the list on `end()++`. This is why the bad behavior is difficult to demonstrate. Reviewers: chandlerc, reames Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D14350 llvm-svn: 252386
* [InstCombine] Teach FoldPHIArgZextsIntoPHI about EHPadsDavid Majnemer2015-11-071-1/+41
| | | | | | | | FoldPHIArgZextsIntoPHI cannot insert an instruction after the PHI if there is an EHPad in the BB. Doing so would result in an instruction inserted after a terminator. llvm-svn: 252377
* [InstCombine] Don't insert an instruction after a terminatorDavid Majnemer2015-11-061-2/+38
| | | | | | | | We tried to insert a cast of a phi in a block whose terminator is an EHPad. This is invalid. Do not attempt the transform in these circumstances. llvm-svn: 252370
* Add 'notail' marker for call instructions.Akira Hatanaka2015-11-061-0/+24
| | | | | | | | | | | | This marker prevents optimization passes from adding 'tail' or 'musttail' markers to a call. Is is used to prevent tail call optimization from being performed on the call. rdar://problem/22667622 Differential Revision: http://reviews.llvm.org/D12923 llvm-svn: 252368
* [InstCombine] Don't RAUW tokens with undefDavid Majnemer2015-11-061-0/+21
| | | | | | Let SimplifyCFG remove unreachable BBs which define token instructions. llvm-svn: 252343
* Fix SLPVectorizer commutativity reorderingMehdi Amini2015-11-061-0/+78
| | | | | | | | | | | | | | | | | | | The SLPVectorizer had a very crude way of trying to benefit from associativity: it tried to optimize for splat/broadcast or in order to have the same operator on the same side. This is benefitial to the cost model and allows more vectorization to occur. This patch improve the logic and make the detection optimal (locally, we don't look at the full tree but only at the immediate children). Should fix https://llvm.org/bugs/show_bug.cgi?id=25247 Reviewers: mzolotukhin Differential Revision: http://reviews.llvm.org/D13996 From: Mehdi Amini <mehdi.amini@apple.com> llvm-svn: 252337
* [ValueTracking] De-pessimize isImpliedCondition around unsigned comparesSanjoy Das2015-11-061-1/+12
| | | | | | | | | | | | | | | Summary: Currently `isImpliedCondition` will optimize "I +_nuw C < L ==> I < L" only if C is positive. This is an unnecessary restriction -- the implication holds even if `C` is negative. Reviewers: reames, majnemer Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D14369 llvm-svn: 252332
* [ValueTracking] Add a framework for encoding implication rulesSanjoy Das2015-11-061-0/+24
| | | | | | | | | | | | | | | | | | | | | Summary: This change adds a framework for adding more smarts to `isImpliedCondition` around inequalities. Informally, `isImpliedCondition` will now try to prove "A < B ==> C < D" by proving "C <= A && B <= D", since then it follows "C <= A < B <= D". While this change is in principle NFC, I could not think of a way to not handle cases like "i +_nsw 1 < L ==> i < L +_nsw 1" (that ValueTracking did not handle before) while keeping the change understandable. I've added tests for these cases. Reviewers: reames, majnemer, hfinkel Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D14368 llvm-svn: 252331
* Re-apply r251050 with a for PR25421Sanjoy Das2015-11-052-0/+88
| | | | | | | | | | | | | | | | | | | | | | | | | The bug: I missed adding break statements in the switch / case. Original commit message: [SCEV] Teach SCEV some axioms about non-wrapping arithmetic Summary: - A s< (A + C)<nsw> if C > 0 - A s<= (A + C)<nsw> if C >= 0 - (A + C)<nsw> s< A if C < 0 - (A + C)<nsw> s<= A if C <= 0 Right now `C` needs to be a constant, but we can later generalize it to be a non-constant if needed. Reviewers: atrick, hfinkel, reames, nlewycky Subscribers: sanjoy, llvm-commits Differential Revision: http://reviews.llvm.org/D13686 llvm-svn: 252236
* Revert r251050 to fix miscompile when running Clang -O1Richard Trieu2015-11-051-58/+0
| | | | | | | See bug for details: https://llvm.org/bugs/show_bug.cgi?id=25421 Some comparisons were incorrectly replaced with a constant value. llvm-svn: 252231
* DI: Reverse direction of subprogram -> function edge.Peter Collingbourne2015-11-0564-183/+186
| | | | | | | | | | | | | | | | | | | | | | | Previously, subprograms contained a metadata reference to the function they described. Because most clients need to get or set a subprogram for a given function rather than the other way around, this created unneeded inefficiency. For example, many passes needed to call the function llvm::makeSubprogramMap() to build a mapping from functions to subprograms, and the IR linker needed to fix up function references in a way that caused quadratic complexity in the IR linking phase of LTO. This change reverses the direction of the edge by storing the subprogram as function-level metadata and removing DISubprogram's function field. Since this is an IR change, a bitcode upgrade has been provided. Fixes PR23367. An upgrade script for textual IR for out-of-tree clients is attached to the PR. Differential Revision: http://reviews.llvm.org/D14265 llvm-svn: 252219
* [SimplifyLibCalls] New transformation: tan(atan(x)) -> xDavide Italiano2015-11-042-0/+32
| | | | | | | | | | | | | | | | | | | | This is enabled only under -ffast-math. So, instead of emitting: 4007b0: 50 push %rax 4007b1: e8 8a fd ff ff callq 400540 <atanf@plt> 4007b6: 58 pop %rax 4007b7: e9 94 fd ff ff jmpq 400550 <tanf@plt> 4007bc: 0f 1f 40 00 nopl 0x0(%rax) for: float mytan(float x) { return tanf(atanf(x)); } we emit a single retq. Differential Revision: http://reviews.llvm.org/D14302 llvm-svn: 252098
* [SimplifyCFG] Merge conditional storesJames Molloy2015-11-041-0/+241
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We can often end up with conditional stores that cannot be speculated. They can come from fairly simple, idiomatic code: if (c & flag1) *a = x; if (c & flag2) *a = y; ... There is no dominating or post-dominating store to a, so it is not legal to move the store unconditionally to the end of the sequence and cache the intermediate result in a register, as we would like to. It is, however, legal to merge the stores together and do the store once: tmp = undef; if (c & flag1) tmp = x; if (c & flag2) tmp = y; if (c & flag1 || c & flag2) *a = tmp; The real power in this optimization is that it allows arbitrary length ladders such as these to be completely and trivially if-converted. The typical code I'd expect this to trigger on often uses binary-AND with constants as the condition (as in the above example), which means the ending condition can simply be truncated into a single binary-AND too: 'if (c & (flag1|flag2))'. As in the general case there are bitwise operators here, the ladder can often be optimized further too. This optimization involves potentially increasing register pressure. Even in the simplest case, the lifetime of the first predicate is extended. This can be elided in some cases such as using binary-AND on constants, but not in the general case. Threading 'tmp' through all branches can also increase register pressure. The optimization as in this patch is enabled by default but kept in a very conservative mode. It will only optimize if it thinks the resultant code should be if-convertable, and additionally if it can thread 'tmp' through at least one existing PHI, so it will only ever in the worst case create one more PHI and extend the lifetime of a predicate. This doesn't trigger much in LNT, unfortunately, but it does trigger in a big way in a third party test suite. llvm-svn: 252051
* [CVP] Fold return values if possiblePhilip Reames2015-11-041-1/+1
| | | | | | | | | | | | In my previous change to CVP (251606), I made CVP much more aggressive about trying to constant fold comparisons. This patch is a reversal in direction. Rather than being agressive about every compare, we restore the non-block local restriction for most, and then try hard for compares feeding returns. The motivation for this is two fold: * The more I thought about it, the less comfortable I got with the possible compile time impact of the other approach. There have been no reported issues, but after talking to a couple of folks, I've come to the conclusion the time probably isn't justified. * It turns out we need to know the context to leverage the full power of LVI. In particular, asking about something at the end of it's block (the use of a compare in a return) will frequently get more precise results than something in the middle of a block. This is an implementation detail, but it's also hard to get around since mid-block queries have to reason about possible throwing instructions and don't get to use most of LVI's block focused infrastructure. This will become particular important when combined with http://reviews.llvm.org/D14263. Differential Revision: http://reviews.llvm.org/D14271 llvm-svn: 252032
* LLE 6/6: Add LoopLoadElimination passAdam Nemet2015-11-036-0/+268
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: The goal of this pass is to perform store-to-load forwarding across the backedge of a loop. E.g.: for (i) A[i + 1] = A[i] + B[i] => T = A[0] for (i) T = T + B[i] A[i + 1] = T The pass relies on loop dependence analysis via LoopAccessAnalisys to find opportunities of loop-carried dependences with a distance of one between a store and a load. Since it's using LoopAccessAnalysis, it was easy to also add support for versioning away may-aliasing intervening stores that would otherwise prevent this transformation. This optimization is also performed by Load-PRE in GVN without the option of multi-versioning. As was discussed with Daniel Berlin in http://reviews.llvm.org/D9548, this is inferior to a more loop-aware solution applied here. Hopefully, we will be able to remove some complexity from GVN/MemorySSA as a consequence. In the long run, we may want to extend this pass (or create a new one if there is little overlap) to also eliminate loop-indepedent redundant loads and store that *require* versioning due to may-aliasing intervening stores/loads. I have some motivating cases for store elimination. My plan right now is to wait for MemorySSA to come online first rather than using memdep for this. The main motiviation for this pass is the 456.hmmer loop in SPECint2006 where after distributing the original loop and vectorizing the top part, we are left with the critical path exposed in the bottom loop. Being able to promote the memory dependence into a register depedence (even though the HW does perform store-to-load fowarding as well) results in a major gain (~20%). This gain also transfers over to x86: it's around 8-10%. Right now the pass is off by default and can be enabled with -enable-loop-load-elim. On the LNT testsuite, there are two performance changes (negative number -> improvement): 1. -28% in Polybench/linear-algebra/solvers/dynprog: the length of the critical paths is reduced 2. +2% in Polybench/stencils/adi: Unfortunately, I couldn't reproduce this outside of LNT The pass is scheduled after the loop vectorizer (which is after loop distribution). The rational is to try to reuse LAA state, rather than recomputing it. The order between LV and LLE is not critical because normally LV does not touch scalar st->ld forwarding cases where vectorizing would inhibit the CPU's st->ld forwarding to kick in. LoopLoadElimination requires LAA to provide the full set of dependences (including forward dependences). LAA is known to omit loop-independent dependences in certain situations. The big comment before removeDependencesFromMultipleStores explains why this should not occur for the cases that we're interested in. Reviewers: dberlin, hfinkel Subscribers: junbuml, dberlin, mssimpso, rengolin, sanjoy, llvm-commits Differential Revision: http://reviews.llvm.org/D13259 llvm-svn: 252017
OpenPOWER on IntegriCloud