aboutsummaryrefslogtreecommitdiff
path: root/llvm/lib/CodeGen/MachineCopyPropagation.cpp
AgeCommit message (Collapse)AuthorFilesLines
2018-03-30[MachineCopyPropagation] Handle COPY with overlapping source/dest.Eli Friedman1-1/+3
MachineCopyPropagation::CopyPropagateBlock has a bunch of special handling for COPY instructions. This handling assumes that COPY instructions do not modify the source of the copy; this is wrong if the COPY destination overlaps the source. To fix the bug, check explicitly for this situation, and fall back to the generic instruction handling. This bug can't happen for most register classes because they don't have this sort of overlap, but there are a few register classes where this is possible. The testcase uses the AArch64 QQQQ register class. Differential Revision: https://reviews.llvm.org/D44911 llvm-svn: 328851
2018-02-27Re-enable "[MachineCopyPropagation] Extend pass to do COPY source forwarding"Geoff Berry1-1/+206
Re-enable commit r323991 now that r325931 has been committed to make MachineOperand::isRenamable() check more conservative w.r.t. code changes and opt-in on a per-target basis. llvm-svn: 326208
2018-02-17Revert "[MachineCopyPropagation] Extend pass to do COPY source forwarding"Quentin Colombet1-206/+1
This reverts commit r323991. This commit breaks target that don't model all the register constraints in TableGen. So far the workaround was to set the hasExtraXXXRegAllocReq, but it proves that it doesn't cover all the cases. For instance, when mutating an instruction (like in the lowering of COPYs) the isRenamable flag is not properly updated. The same problem will happen when attaching machine operand from one instruction to another. Geoff Berry is working on a fix in https://reviews.llvm.org/D43042. llvm-svn: 325421
2018-02-01[MachineCopyPropagation] Extend pass to do COPY source forwardingGeoff Berry1-1/+206
Summary: This change extends MachineCopyPropagation to do COPY source forwarding and adds an additional run of the pass to the default pass pipeline just after register allocation. This version of this patch uses the newly added MachineOperand::isRenamable bit to avoid forwarding registers is such a way as to violate constraints that aren't captured in the Machine IR (e.g. ABI or ISA constraints). This change is a continuation of the work started in D30751. Reviewers: qcolombet, javed.absar, MatzeB, jonpa, tstellar Subscribers: tpr, mgorny, mcrosier, nhaehnle, nemanjai, jyknight, hfinkel, arsenm, inouehrs, eraman, sdardis, guyblank, fedor.sergeev, aheejin, dschuff, jfb, myatsina, llvm-commits Differential Revision: https://reviews.llvm.org/D41835 llvm-svn: 323991
2017-12-15MachineFunction: Return reference from getFunction(); NFCMatthias Braun1-1/+1
The Function can never be nullptr so we can return a reference. llvm-svn: 320884
2017-12-13Remove redundant includes from lib/CodeGen.Michael Zolotukhin1-1/+0
llvm-svn: 320619
2017-12-07[CodeGen] Use MachineOperand::print in the MIRPrinter for MO_Register.Francis Visoiu Mistrih1-9/+9
Work towards the unification of MIR and debug output by refactoring the interfaces. For MachineOperand::print, keep a simple version that can be easily called from `dump()`, and a more complex one which will be called from both the MIRPrinter and MachineInstr::print. Add extra checks inside MachineOperand for detached operands (operands with getParent() == nullptr). https://reviews.llvm.org/D40836 * find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/kill: ([^ ]+) ([^ ]+)<def> ([^ ]+)/kill: \1 def \2 \3/g' * find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/kill: ([^ ]+) ([^ ]+) ([^ ]+)<def>/kill: \1 \2 def \3/g' * find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/kill: def ([^ ]+) ([^ ]+) ([^ ]+)<def>/kill: def \1 \2 def \3/g' * find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/<def>//g' * find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<kill>/killed \1/g' * find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<imp-use,kill>/implicit killed \1/g' * find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<dead>/dead \1/g' * find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<def[ ]*,[ ]*dead>/dead \1/g' * find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<imp-def[ ]*,[ ]*dead>/implicit-def dead \1/g' * find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<imp-def>/implicit-def \1/g' * find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<imp-use>/implicit \1/g' * find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<internal>/internal \1/g' * find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<undef>/undef \1/g' llvm-svn: 320022
2017-11-28[CodeGen] Print register names in lowercase in both MIR and debug outputFrancis Visoiu Mistrih1-8/+8
As part of the unification of the debug format and the MIR format, always print registers as lowercase. * Only debug printing is affected. It now follows MIR. Differential Revision: https://reviews.llvm.org/D40417 llvm-svn: 319187
2017-11-17Fix a bunch more layering of CodeGen headers that are in TargetDavid Blaikie1-2/+2
All these headers already depend on CodeGen headers so moving them into CodeGen fixes the layering (since CodeGen depends on Target, not the other way around). llvm-svn: 318490
2017-11-10[AMDGPU] Prevent Machine Copy Propagation from replacing live copy with the ↵Alexander Timofeev1-0/+2
dead one Differential revision: https://reviews.llvm.org/D38754 llvm-svn: 317884
2017-11-08Target/TargetInstrInfo.h -> CodeGen/TargetInstrInfo.h to match layeringDavid Blaikie1-1/+1
This header includes CodeGen headers, and is not, itself, included by any Target headers, so move it into CodeGen to match the layering of its implementation. llvm-svn: 317647
2017-10-16[AMDGPU] : revert r315908Alexander Timofeev1-12/+10
llvm-svn: 315916
2017-10-16[AMDGPU] Prevent Machine Copy Propagation from replacing live copy with the ↵Alexander Timofeev1-11/+13
dead one Differential revision: https://reviews.llvm.org/D38754 llvm-svn: 315908
2017-10-03Revert "Re-enable "[MachineCopyPropagation] Extend pass to do COPY source ↵Geoff Berry1-626/+23
forwarding"" This reverts commit r314729. Another bug has been encountered in an out-of-tree target reported by Quentin. llvm-svn: 314814
2017-10-02Re-enable "[MachineCopyPropagation] Extend pass to do COPY source forwarding"Geoff Berry1-23/+626
Issues addressed since original review: - Avoid bug in regalloc greedy/machine verifier when forwarding to use in an instruction that re-defines the same virtual register. - Fixed bug when forwarding to use in EarlyClobber instruction slot. - Fixed incorrect forwarding to register definitions that showed up in explicit_uses() iterator (e.g. in INLINEASM). - Moved removal of dead instructions found by LiveIntervals::shrinkToUses() outside of loop iterating over instructions to avoid instructions being deleted while pointed to by iterator. - Fixed ARMLoadStoreOptimizer bug exposed by this change in r311907. - The pass no longer forwards COPYs to physical register uses, since doing so can break code that implicitly relies on the physical register number of the use. - The pass no longer forwards COPYs to undef uses, since doing so can break the machine verifier by creating LiveRanges that don't end on a use (since the undef operand is not considered a use). [MachineCopyPropagation] Extend pass to do COPY source forwarding This change extends MachineCopyPropagation to do COPY source forwarding. This change also extends the MachineCopyPropagation pass to be able to be run during register allocation, after physical registers have been assigned, but before the virtual registers have been re-written, which allows it to remove virtual register COPY LiveIntervals that become dead through the forwarding of all of their uses. llvm-svn: 314729
2017-09-04Revert "Re-enable "[MachineCopyPropagation] Extend pass to do COPY source ↵Sam McCall1-570/+23
forwarding"" This crashes on boringSSL on PPC (will send reduced testcase) This reverts commit r312328. llvm-svn: 312490
2017-09-01Re-enable "[MachineCopyPropagation] Extend pass to do COPY source forwarding"Geoff Berry1-23/+570
Issues addressed since original review: - Moved removal of dead instructions found by LiveIntervals::shrinkToUses() outside of loop iterating over instructions to avoid instructions being deleted while pointed to by iterator. - Fixed ARMLoadStoreOptimizer bug exposed by this change in r311907. - The pass no longer forwards COPYs to physical register uses, since doing so can break code that implicitly relies on the physical register number of the use. - The pass no longer forwards COPYs to undef uses, since doing so can break the machine verifier by creating LiveRanges that don't end on a use (since the undef operand is not considered a use). [MachineCopyPropagation] Extend pass to do COPY source forwarding This change extends MachineCopyPropagation to do COPY source forwarding. This change also extends the MachineCopyPropagation pass to be able to be run during register allocation, after physical registers have been assigned, but before the virtual registers have been re-written, which allows it to remove virtual register COPY LiveIntervals that become dead through the forwarding of all of their uses. llvm-svn: 312328
2017-08-30Revert r312154 "Re-enable "[MachineCopyPropagation] Extend pass to do COPY ↵Hans Wennborg1-567/+23
source forwarding"" It caused PR34387: Assertion failed: (RegNo < NumRegs && "Attempting to access record for invalid register number!") > Issues identified by buildbots addressed since original review: > - Fixed ARMLoadStoreOptimizer bug exposed by this change in r311907. > - The pass no longer forwards COPYs to physical register uses, since > doing so can break code that implicitly relies on the physical > register number of the use. > - The pass no longer forwards COPYs to undef uses, since doing so > can break the machine verifier by creating LiveRanges that don't > end on a use (since the undef operand is not considered a use). > > [MachineCopyPropagation] Extend pass to do COPY source forwarding > > This change extends MachineCopyPropagation to do COPY source forwarding. > > This change also extends the MachineCopyPropagation pass to be able to > be run during register allocation, after physical registers have been > assigned, but before the virtual registers have been re-written, which > allows it to remove virtual register COPY LiveIntervals that become dead > through the forwarding of all of their uses. llvm-svn: 312178
2017-08-30Re-enable "[MachineCopyPropagation] Extend pass to do COPY source forwarding"Geoff Berry1-23/+567
Issues identified by buildbots addressed since original review: - Fixed ARMLoadStoreOptimizer bug exposed by this change in r311907. - The pass no longer forwards COPYs to physical register uses, since doing so can break code that implicitly relies on the physical register number of the use. - The pass no longer forwards COPYs to undef uses, since doing so can break the machine verifier by creating LiveRanges that don't end on a use (since the undef operand is not considered a use). [MachineCopyPropagation] Extend pass to do COPY source forwarding This change extends MachineCopyPropagation to do COPY source forwarding. This change also extends the MachineCopyPropagation pass to be able to be run during register allocation, after physical registers have been assigned, but before the virtual registers have been re-written, which allows it to remove virtual register COPY LiveIntervals that become dead through the forwarding of all of their uses. llvm-svn: 312154
2017-08-29[CodeGen] Fix some Clang-tidy modernize-use-using and Include What You Use ↵Eugene Zelenko1-6/+22
warnings; other minor fixes (NFC). llvm-svn: 312053
2017-08-18Revert "[MachineCopyPropagation] Extend pass to do COPY source forwarding" ↵Geoff Berry1-567/+24
round 2 This reverts commit r311135. sanitizer-x86_64-linux-android buildbot is timing out with just this patch applied. llvm-svn: 311142
2017-08-17 Re-enable "[MachineCopyPropagation] Extend pass to do COPY source ↵Geoff Berry1-24/+567
forwarding" Two issues identified by buildbots were addressed: - The pass no longer forwards COPYs to physical register uses, since doing so can break code that implicitly relies on the physical register number of the use. - The pass no longer forwards COPYs to undef uses, since doing so can break the machine verifier by creating LiveRanges that don't end on a use (since the undef operand is not considered a use). [MachineCopyPropagation] Extend pass to do COPY source forwarding This change extends MachineCopyPropagation to do COPY source forwarding. This change also extends the MachineCopyPropagation pass to be able to be run during register allocation, after physical registers have been assigned, but before the virtual registers have been re-written, which allows it to remove virtual register COPY LiveIntervals that become dead through the forwarding of all of their uses. Reviewers: qcolombet, javed.absar, MatzeB, jonpa Subscribers: jyknight, nemanjai, llvm-commits, nhaehnle, mcrosier, mgorny Differential Revision: https://reviews.llvm.org/D30751 llvm-svn: 311135
2017-08-17Revert "[MachineCopyPropagation] Extend pass to do COPY source forwarding"Geoff Berry1-539/+24
This reverts commit r311038. Several buildbots are breaking, and at least one appears to be due to the forwarding of physical regs enabled by this change. Reverting while I investigate further. llvm-svn: 311062
2017-08-16[MachineCopyPropagation] Extend pass to do COPY source forwardingGeoff Berry1-24/+539
This change extends MachineCopyPropagation to do COPY source forwarding. This change also extends the MachineCopyPropagation pass to be able to be run during register allocation, after physical registers have been assigned, but before the virtual registers have been re-written, which allows it to remove virtual register COPY LiveIntervals that become dead through the forwarding of all of their uses. Reviewers: qcolombet, javed.absar, MatzeB, jonpa Subscribers: jyknight, nemanjai, llvm-commits, nhaehnle, mcrosier, mgorny Differential Revision: https://reviews.llvm.org/D30751 llvm-svn: 311038
2017-06-06Sort the remaining #include lines in include/... and lib/....Chandler Carruth1-1/+1
I did this a long time ago with a janky python script, but now clang-format has built-in support for this. I fed clang-format every line with a #include and let it re-sort things according to the precise LLVM rules for include ordering baked into clang-format these days. I've reverted a number of files where the results of sorting includes isn't healthy. Either places where we have legacy code relying on particular include ordering (where possible, I'll fix these separately) or where we have particular formatting around #include lines that I didn't want to disturb in this patch. This patch is *entirely* mechanical. If you get merge conflicts or anything, just ignore the changes in this patch and run clang-format over your #include lines in the files. Sorry for any noise here, but it is important to keep these things stable. I was seeing an increasing number of patches with irrelevant re-ordering of #include lines because clang-format was used. This patch at least isolates that churn, makes it easy to skip when resolving conflicts, and gets us to a clean baseline (again). llvm-svn: 304787
2017-05-25CodeGen: Rename DEBUG_TYPE to match passnamesMatthias Braun1-2/+2
Rename the DEBUG_TYPE to match the names of corresponding passes where it makes sense. Also establish the pattern of simply referencing DEBUG_TYPE instead of repeating the passname where possible. llvm-svn: 303921
2017-02-04MachineCopyPropagation: Respect implicit operands of COPYMatthias Braun1-17/+31
The code missed to check implicit operands of COPY instructions for defs/uses. Differential Revision: https://reviews.llvm.org/D29522 llvm-svn: 294088
2017-02-04MachineCopyPropagation: Do not consider undef operands as clobbersMatthias Braun1-8/+0
This was originally introduced in r278321 to work around correctness problems in the ExecutionDepsFix pass; Probably also to keep the performance benefits of breaking the false dependencies which of course also affect undef operands. ExecutionDepsFix has been improved here recently (see for example r278321) so we should not need this exception any longer. Differential Revision: https://reviews.llvm.org/D29525 llvm-svn: 294087
2016-08-25MachineFunctionProperties/MIRParser: Rename AllVRegsAllocated->NoVRegs, ↵Matthias Braun1-1/+1
compute it Rename AllVRegsAllocated to NoVRegs. This avoids the connotation of running after register and simply describes that no vregs are used in a machine function. With that we can simply compute the property and do not need to dump/parse it in .mir files. Differential Revision: http://reviews.llvm.org/D23850 llvm-svn: 279698
2016-08-11Use the range variant of find instead of unpacking begin/endDavid Majnemer1-1/+1
If the result of the find is only used to compare against end(), just use is_contained instead. No functionality change is intended. llvm-svn: 278433
2016-06-02Make MachineCopyPropagation preserve CFGMatt Arsenault1-0/+5
This doesn't touch it as far as I can tell. llvm-svn: 271445
2016-04-22Re-commit optimization bisect support (r267022) without new pass manager ↵Andrew Kaylor1-1/+1
support. The original commit was reverted because of a buildbot problem with LazyCallGraph::SCC handling (not related to the OptBisect handling). Differential Revision: http://reviews.llvm.org/D19172 llvm-svn: 267231
2016-04-22Revert "Initial implementation of optimization bisect support."Vedant Kumar1-1/+1
This reverts commit r267022, due to an ASan failure: http://lab.llvm.org:8080/green/job/clang-stage2-cmake-RgSan_check/1549 llvm-svn: 267115
2016-04-21Initial implementation of optimization bisect support.Andrew Kaylor1-1/+1
This patch implements a optimization bisect feature, which will allow optimizations to be selectively disabled at compile time in order to track down test failures that are caused by incorrect optimizations. The bisection is enabled using a new command line option (-opt-bisect-limit). Individual passes that may be skipped call the OptBisect object (via an LLVMContext) to see if they should be skipped based on the bisect limit. A finer level of control (disabling individual transformations) can be managed through an addition OptBisect method, but this is not yet used. The skip checking in this implementation is based on (and replaces) the skipOptnoneFunction check. Where that check was being called, a new call has been inserted in its place which checks the bisect limit and the optnone attribute. A new function call has been added for module and SCC passes that behaves in a similar way. Differential Revision: http://reviews.llvm.org/D19172 llvm-svn: 267022
2016-03-28Introduce MachineFunctionProperties and the AllVRegsAllocated propertyDerek Schuff1-0/+5
MachineFunctionProperties represents a set of properties that a MachineFunction can have at particular points in time. Existing examples of this idea are MachineRegisterInfo::isSSA() and MachineRegisterInfo::tracksLiveness() which will eventually be switched to use this mechanism. This change introduces the AllVRegsAllocated property; i.e. the property that all virtual registers have been allocated and there are no VReg operands left. With this mechanism, passes can declare that they require a particular property to be set, or that they set or clear properties by implementing e.g. MachineFunctionPass::getRequiredProperties(). The MachineFunctionPass base class verifies that the requirements are met, and handles the setting and clearing based on the delcarations. Passes can also directly query and update the current properties of the MF if they want to have conditional behavior. This change annotates the target-independent post-regalloc passes; future changes will also annotate target-specific ones. Reviewers: qcolombet, hfinkel Differential Revision: http://reviews.llvm.org/D18421 llvm-svn: 264593
2016-03-25[MachineCopyPropagation] Expose more dead copies across instructions with ↵Jun Bum Lim1-3/+14
regmasks When encountering instructions with regmasks, instead of cleaning up all the elements in MaybeDeadCopies map, remove only the instructions erased. By keeping more instruction in MaybeDeadCopies, this change will expose more dead copies across instructions with regmasks. llvm-svn: 264462
2016-02-26MachineCopyPropagation: Catch copies of the form A<-B;A<-BMatthias Braun1-54/+71
Differential Revision: http://reviews.llvm.org/D17475 llvm-svn: 261966
2016-02-26MachineCopyPropagation: Keep scanning through instructions with regmasksMatthias Braun1-55/+55
This also simplifies the code by removing the overly conservative NoInterveningSideEffect() function. This function checked: - That the two copies belong to the same block: We only process one block at a time and clear our maps in between it is impossible to find a copy from a different block. - There is no terminator between the two copy instructions: This is not allowed anyway (the MachineVerifier would complain) - Does not have instructions with hasUnmodeledSideEffects() or isCall() set: Even for those instructuction we must have all clobbers/defs of registers explicit as an operand. If the register is explicitely clobbered we would never come to the point of checking for NoInterveningSideEffect() anyway. (I also checked this with a temporary build of the test-suite with all potentially failing conditions in NoInterveningSideEffect() turned into asserts) Differential Revision: http://reviews.llvm.org/D17474 llvm-svn: 261965
2016-02-22Revert "CodeGen: MachineInstr::getIterator() => getInstrIterator(), NFC"Duncan P. N. Exon Smith1-6/+4
This reverts commit r261504, since it's not obvious the new name is better: http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160222/334298.html I'll recommit if we get consensus that it's the right direction. llvm-svn: 261567
2016-02-21CodeGen: MachineInstr::getIterator() => getInstrIterator(), NFCDuncan P. N. Exon Smith1-4/+6
Delete MachineInstr::getIterator(), since the term "iterator" is overloaded when talking about MachineInstr. - Downcast to ilist_node in iplist::getNextNode() and getPrevNode() so that ilist_node::getIterator() is still available. - Add it back as MachineInstr::getInstrIterator(). This matches the naming in MachineBasicBlock. - Add MachineInstr::getBundleIterator(). This is explicitly called "bundle" (not matching MachineBasicBlock) to disintinguish it clearly from ilist_node::getIterator(). - Update all calls. Some of these I switched to `auto` to remove boiler-plate, since the new name is clear about the type. There was one call I updated that looked fishy, but it wasn't clear what the right answer was. This was in X86FrameLowering::inlineStackProbe(), added in r252578 in lib/Target/X86/X86FrameLowering.cpp. I opted to leave the behaviour unchanged, but I'll reply to the original commit on the list in a moment. llvm-svn: 261504
2016-02-20MachineCopyPropagation: Introduce Reg2MIMap typedef; NFCMatthias Braun1-4/+5
llvm-svn: 261408
2016-02-20MachineCopyPropagation: Move variables from function to passMatthias Braun1-18/+22
This avoids unnecessarily passing them around when calling helper functions. It may also be slightly faster to call clear() on the datastructures instead of freshly initializing them for each block. llvm-svn: 261407
2016-02-20MachineCopyPropagation: Use ranged for, cleanup; NFCMatthias Braun1-51/+35
llvm-svn: 261406
2016-02-20MachineCopyPropagation: Use assert() instead of if{report_error()} for ↵Matthias Braun1-8/+5
'impossible' condition llvm-svn: 261405
2016-02-03[MachineCopyPropagation] Fix comment. NFCJun Bum Lim1-2/+3
Reviewers: MatzeB, qcolombet, jmolloy, mcrosier Subscribers: llvm-commits, mcrosier Differential Revision: http://reviews.llvm.org/D16806 llvm-svn: 259656
2015-06-23Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC)Alexander Kornienko1-1/+1
Apparently, the style needs to be agreed upon first. llvm-svn: 240390
2015-06-19Fixed/added namespace ending comments using clang-tidy. NFCAlexander Kornienko1-1/+1
The patch is generated using this command: tools/clang/tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \ -checks=-*,llvm-namespace-comment -header-filter='llvm/.*|clang/.*' \ llvm/lib/ Thanks to Eugene Kosov for the original patch! llvm-svn: 240137
2015-05-29MachineCopyPropagation: Remove the copies instead of using KILL instructions.Matthias Braun1-11/+3
For some history here see the commit messages of r199797 and r169060. The original intent was to fix cases like: %EAX<def> = COPY %ECX<kill>, %RAX<imp-def> %RCX<def> = COPY %RAX<kill> where simply removing the copies would have RCX undefined as in terms of machine operands only the ECX part of it is defined. The machine verifier would complain about this so 169060 changed such COPY instructions into KILL instructions so some super-register imp-defs would be preserved. In r199797 it was finally decided to always do this regardless of super-register defs. But this is wrong, consider: R1 = COPY R0 ... R0 = COPY R1 getting changed to: R1 = KILL R0 ... R0 = KILL R1 It now looks like R0 dies at the first KILL and won't be alive until the second KILL, while in reality R0 is alive and must not change in this part of the program. As this only happens after register allocation there is not much code still performing liveness queries so the issue was not noticed. In fact I didn't manage to create a testcase for this, without unrelated changes I am working on at the moment. The fix is simple: As of r223896 the MachineVerifier allows reads from partially defined registers, so the whole transforming COPY->KILL thing is not necessary anymore. This patch also changes a similar (but more benign case as the def and src are the same register) case in the VirtRegRewriter. Differential Revision: http://reviews.llvm.org/D10117 llvm-svn: 238588
2015-05-28[MachineCopyPropagation] Fix a bug with undef handling when the value is ↵Quentin Colombet1-5/+9
actualy alive. Test case will follow. llvm-svn: 238518
2015-04-23[MachineCopyPropagation] Handle undef flags conservatively so that we do notQuentin Colombet1-1/+5
remove copies that are useful after breaking some hardware dependencies. In other words, handle this kind of situations conservatively by assuming reg2 is redefined by the undef flag. reg1 = copy reg2 = inst reg2<undef> reg2 = copy reg1 Copy propagation used to remove the last copy. This is incorrect because the undef flag on reg2 in inst, allows next passes to put whatever trashed value in reg2 that may help. In practice we end up with this code: reg1 = copy reg2 reg2 = 0 = inst reg2<undef> reg2 = copy reg1 This fixes PR21743. llvm-svn: 235647