Commit Graph

24995 Commits

Author SHA1 Message Date
NAKAMURA Takumi 1ed20db720 Revert r248959, "[WinEH] Emit int3 after noreturn calls on Win64"
It broke; LLVM :: CodeGen__Generic__2009-11-16-BadKillsCrash.ll

llvm-svn: 249032
2015-10-01 17:00:56 +00:00
Rafael Espindola 812f57e6dc Use more strict types. NFC.
On 32 bit ELF these are 32 bit values.

llvm-svn: 249022
2015-10-01 15:22:42 +00:00
Keno Fischer 17433bd102 Fix performance problem in long-running SectionMemoryManagers
Summary:
Without this patch, the memory manager would call `mprotect` on every memory
region it ever allocated whenever it wanted to finalize memory (i.e. not just
the ones it just allocated). This caused terrible performance problems for
long running memory managers. In one particular compile heavy julia benchmark,
we were spending 50% of time in `mprotect` if running under MCJIT.

Fix this by splitting allocated memory blocks into those on which memory
permissions have been set and those on which they haven't and only running
`mprotect` on the latter.

Reviewers: lhames

Subscribers: reames, llvm-commits

Differential Revision: http://reviews.llvm.org/D13156

llvm-svn: 248981
2015-10-01 02:45:07 +00:00
Dehao Chen 7c41dd6498 Update sample profile propagation algorithm.
http://reviews.llvm.org/D13218

llvm-svn: 248968
2015-10-01 00:26:56 +00:00
Reid Kleckner 6dec87a8a0 [WinEH] Emit int3 after noreturn calls on Win64
The Win64 unwinder disassembles forwards from each PC to try to
determine if this PC is in an epilogue. If so, it skips calling the EH
personality function for that frame. Typically, this means you cannot
catch an exception in the same frame that you threw it, because 'throw'
calls a noreturn runtime function.

Previously we avoided this problem with the TrapUnreachable
TargetOption, but that's a much bigger hammer than we need. All we need
is a 1 byte non-epilogue instruction right after the call.  Instead,
what we got was an unconditional branch to a shared block containing the
ud2, potentially 7 bytes instead of 1. So, this reverts r206684, which
added TrapUnreachable, and replaces it with something better.

The new code pattern matches for invoke/call followed by unreachable and
inserts an int3 into the DAG. To be 100% watertight, we would need to
insert SEH_Epilogue instructions into all basic blocks ending in a call
with no terminators or successors, but in practice this is unlikely to
come up.

llvm-svn: 248959
2015-09-30 23:09:23 +00:00
Hal Finkel 39ac97fa3a [PowerPC] undef Relocation names in PowerPC*.def
glibc's PowerPC /usr/include/asm/sigcontext.h, has this:

  #ifdef __powerpc64__
  #include <asm/elf.h>
  #endif

and that contains defines of all of the relocation symbols, like this:

  #define R_PPC_NONE              0

and if that file is included prior to including
include/llvm/Support/ELFRelocs/PowerPC*.def, which we cannot in general
prevent, the result will fail.

As it turns out, this happens when compiling
lld/unittests/DriverTests/GnuLdDriverTest.cpp under PPC64/Linux, because:

  lld/include/lld/ReaderWriter/ELFLinkingContext.h includes
  lld/unittests/DriverTests/DriverTest.h which includes
  utils/unittest/googletest/include/gtest/gtest.h which includes
  utils/unittest/googletest/include/gtest/internal/gtest-internal.h which includes
  /usr/include/sys/wait.h which includes
  /usr/include/signal.h which includes
  /usr/include/bits/sigcontext.h which includes
  /usr/include/asm/sigcontext.h which includes
  /usr/include/asm/elf.h

the test could be fixed to include ReaderWriter/ELFLinkingContext.h before
including unittests/DriverTests/DriverTest.h, but dealing with this in the
*.def files is a more-general solution that localizes the fix to the headers
instead of requiring changes to an unbounded number of other source files (both
in-tree and external).

llvm-svn: 248957
2015-09-30 22:34:35 +00:00
Evgeniy Stepanov f608111d1b Fix debug info with SafeStack.
llvm-svn: 248933
2015-09-30 19:55:43 +00:00
Artyom Skrobov 72ca6b8f3f [ARM] Support for ARMv6-Z / ARMv6-ZK missing
As Richard Barton observed at http://reviews.llvm.org/D12937#inline-107121
TargetParser in LLVM has insufficient support for ARMv6Z and ARMv6ZK.

In particular, there were no tests for TrustZone being supported in these
architectures.

The patch clears a FIXME: left by Saleem Abdulrasool in r201471, and fixes
his test case which hadn't really been testing what it was claiming to test.

Differential Revision: http://reviews.llvm.org/D13236

llvm-svn: 248921
2015-09-30 17:25:52 +00:00
Teresa Johnson eaa3d2a63c Add support for sub-byte aligned writes to lib/Support/Endian.h
Summary:
As per Duncan's review for D12536, I extracted the sub-byte bit aligned
reading and writing code into lib/Support, and generalized it. Added calls from
BackpatchWord. Also added unittests.

Reviewers: dexonsmith

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13189

llvm-svn: 248897
2015-09-30 13:20:37 +00:00
Jeroen Ketema ab99b59e8c [ARM][NEON] Use address space in vld([1234]|[234]lane) and vst([1234]|[234]lane) instructions
This commit changes the interface of the vld[1234], vld[234]lane, and vst[1234],
vst[234]lane ARM neon intrinsics and associates an address space with the
pointer that these intrinsics take. This changes, e.g.,

<2 x i32> @llvm.arm.neon.vld1.v2i32(i8*, i32)

to

<2 x i32> @llvm.arm.neon.vld1.v2i32.p0i8(i8*, i32)

This change ensures that address spaces are fully taken into account in the ARM
target during lowering of interleaved loads and stores.

Differential Revision: http://reviews.llvm.org/D12985

llvm-svn: 248887
2015-09-30 10:56:37 +00:00
Dehao Chen 6722688eaa http://reviews.llvm.org/D13145
Support hierarachical sample profile format.

llvm-svn: 248865
2015-09-30 00:42:46 +00:00
Justin Bogner 10c7e148c4 InstrProf: Add a missing const_cast from r248833
llvm-svn: 248859
2015-09-29 23:42:47 +00:00
Justin Bogner 9e9a057a9b InstrProf: Support for value profiling in the indexed profile format
Add support to the indexed instrprof reader and writer for the format
that will be used for value profiling.

Patch by Betul Buyukkurt, with minor modifications.

llvm-svn: 248833
2015-09-29 22:13:58 +00:00
Maksim Panchenko cce239c45d HHVM calling conventions.
HHVM calling convention, hhvmcc, is used by HHVM JIT for
functions in translated cache. We currently support LLVM back end to
generate code for X86-64 and may support other architectures in the
future.

In HHVM calling convention any GP register could be used to pass and
return values, with the exception of R12 which is reserved for
thread-local area and is callee-saved. Other than R12, we always
pass RBX and RBP as args, which are our virtual machine's stack pointer
and frame pointer respectively.

When we enter translation cache via hhvmcc function, we expect
the stack to be aligned at 16 bytes, i.e. skewed by 8 bytes as opposed
to standard ABI alignment. This affects stack object alignment and stack
adjustments for function calls.

One extra calling convention, hhvm_ccc, is used to call C++ helpers from
HHVM's translation cache. It is almost identical to standard C calling
convention with an exception of first argument which is passed in RBP
(before we use RDI, RSI, etc.)

Differential Revision: http://reviews.llvm.org/D12681

llvm-svn: 248832
2015-09-29 22:09:16 +00:00
David Majnemer a80c151286 [WinEH] Teach AsmPrinter about funclets
Summary:
Funclets have been turned into functions by the time they hit the object
file.  Make sure that they have decent names for the symbol table and
CFI directives explaining how to reason about their prologues.

Differential Revision: http://reviews.llvm.org/D13261

llvm-svn: 248824
2015-09-29 20:12:33 +00:00
Cong Hou 166e08542e Rename some function arguments in MachineBasicBlock.cpp/h by turning the first letter into upper case. NFC.
llvm-svn: 248821
2015-09-29 19:46:09 +00:00
Dehao Chen 8e7df83e6a http://reviews.llvm.org/D13231
Change lookup functions to const functions.

llvm-svn: 248818
2015-09-29 18:28:15 +00:00
Hans Wennborg cc9deb4801 Fix Clang-tidy modernize-use-nullptr warnings in examples and include directories; other minor cleanups.
Patch by Eugene Zelenko!

Differential Revision: http://reviews.llvm.org/D13172

llvm-svn: 248811
2015-09-29 18:02:48 +00:00
Nemanja Ivanovic 2c84b29464 Addition of interfaces the BE to conform to Table A-2 of ELF V2 ABI V1.1
This patch corresponds to review:
http://reviews.llvm.org/D13191

Back end portion of the fifth round of additions to altivec.h.

llvm-svn: 248809
2015-09-29 17:41:53 +00:00
Jeroen Ketema 740f9d79ca Arguments spilled on the stack before a function call may have
alignment requirements, for example in the case of vectors.
These requirements are exploited by the code generator by using
move instructions that have similar alignment requirements, e.g.,
movaps on x86.

Although the code generator properly aligns the arguments with
respect to the displacement of the stack pointer it computes,
the displacement itself may cause misalignment. For example if
we have

%3 = load <16 x float>, <16 x float>* %1, align 64
call void @bar(<16 x float> %3, i32 0)

the x86 back-end emits:

movaps  32(%ecx), %xmm2
movaps  (%ecx), %xmm0
movaps  16(%ecx), %xmm1
movaps  48(%ecx), %xmm3
subl    $20, %esp       <-- if %esp was 16-byte aligned before this instruction, it no longer will be afterwards 
movaps  %xmm3, (%esp)   <-- movaps requires 16-byte alignment, while %esp is not aligned as such.
movl    $0, 16(%esp)
calll   __bar

To solve this, we need to make sure that the computed value with which
the stack pointer is changed is a multiple af the maximal alignment seen
during its computation. With this change we get proper alignment:

subl    $32, %esp
movaps  %xmm3, (%esp)

Differential Revision: http://reviews.llvm.org/D12337

llvm-svn: 248786
2015-09-29 10:12:57 +00:00
Reid Kleckner c71d6275ca [WinEH] Fix ip2state table emission with funclets
Previously we were hijacking the old LandingPadInfo data structures to
communicate our state numbers. Now we don't need that anymore.

llvm-svn: 248763
2015-09-28 23:56:30 +00:00
Andrew Kaylor 16c4da03d5 Improved the interface of methods commuting operands, improved X86-FMA3 mem-folding&coalescing.
Patch by Slava Klochkov (vyacheslav.n.klochkov@intel.com)

Differential Revision: http://reviews.llvm.org/D11370

llvm-svn: 248735
2015-09-28 20:33:22 +00:00
Artur Pilipenko b4d009042b Introduce !align metadata for load instruction
Reviewed By: hfinkel

Differential Revision: http://reviews.llvm.org/D12853

llvm-svn: 248721
2015-09-28 17:41:08 +00:00
Justin Bogner d7d1a72f66 AsmWriter: Print the argument names in declarations while debugging
When llvm declarations have argument names, it's helpful to actually
print those names when debugging. Arguably, it'd be nice to print them
all the time, but that would mean the IR we output wouldn't round trip
through bitcode, which doesn't store the names.

Make the varous print() methods in AsmWriter optionally print "for
debug" and set that flag in the dump() methods. The only thing this
does differently for now is print the argument names in declarations.

llvm-svn: 248692
2015-09-27 22:38:50 +00:00
Joseph Tremoulet 09af67aba5 [EH] Create removeUnwindEdge utility
Summary:
Factor the code that rewrites invokes to calls and rewrites WinEH
terminators to their "unwind to caller" equivalents into a helper in
Utils/Local, and use it in the three places I'm aware of that need to do
this.


Reviewers: andrew.w.kaylor, majnemer, rnk

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13152

llvm-svn: 248677
2015-09-27 01:47:46 +00:00
Benjamin Kramer 2a63631abd [BranchProbability] Manually round the floating point output.
llvm::format compiles down to snprintf which has no defined rounding for
floating point arguments, and MSVC has implemented it differently from
what the BSD libcs and glibc do. Try to emulate the glibc rounding
behavior to avoid changing tests.

While there simplify code a bit and move trivial methods inline.

llvm-svn: 248665
2015-09-26 10:09:36 +00:00
Sanjoy Das 96709c4854 [SCEV] Reapply 'Exploit A < B => (A+K) < (B+K) when possible'
Summary:

This change teaches SCEV's `isImpliedCond` two new identities:

  A u< B u< -C          =>  (A + C) u< (B + C)
  A s< B s< INT_MIN - C =>  (A + C) s< (B + C)

While these are useful on their own, they're really intended to support
D12950.

The original checkin, r248606 had to be backed out due to an issue with
a ObjCXX unit test.  That issue is now fixed, so re-landing.

Reviewers: atrick, reames, majnemer, nlewycky, hfinkel

Subscribers: aadg, sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D12948

llvm-svn: 248637
2015-09-25 23:53:45 +00:00
Matthias Braun 93ab942c24 LivePhysRegs: Fix live-outs of return blocks
I realized that the live-out set computed for the return block is
missing the callee saved registers (the non-pristine ones to be exact).

This only affects the liveness computed for instructions inside the
function epilogue which currently none of the LivePhysRegs users in llvm
cares about, so this is just a drive-by fix without a testcase.

Differential Revision: http://reviews.llvm.org/D13180

llvm-svn: 248636
2015-09-25 23:50:53 +00:00
Cong Hou 15ea016346 Use fixed-point representation for BranchProbability.
BranchProbability now is represented by its numerator and denominator in uint32_t type. This patch changes this representation into a fixed point that is represented by the numerator in uint32_t type and a constant denominator 1<<31. This is quite similar to the representation of BlockMass in BlockFrequencyInfoImpl.h. There are several pros and cons of this change:

Pros:

1. It uses only a half space of the current one.
2. Some operations are much faster like plus, subtraction, comparison, and scaling by an integer.

Cons:

1. Constructing a probability using arbitrary numerator and denominator needs additional calculations.
2. It is a little less precise than before as we use a fixed denominator. For example, 1 - 1/3 may not be exactly identical to 1 / 3 (this will lead to many BranchProbability unit test failures). This should not matter when we only use it for branch probability. If we use it like a rational value for some precise calculations we may need another construct like ValueRatio.

One important reason for this change is that we propose to store branch probabilities instead of edge weights in MachineBasicBlock. We also want clients to use probability instead of weight when adding successors to a MBB. The current BranchProbability has more space which may be a concern.

Differential revision: http://reviews.llvm.org/D12603

llvm-svn: 248633
2015-09-25 23:09:59 +00:00
Matthias Braun c804cdb912 TargetRegisterInfo: Introduce PrintLaneMask.
This makes it more convenient to print lane masks and lead to more
uniform printing.

llvm-svn: 248624
2015-09-25 21:51:24 +00:00
Matthias Braun e6a2485e1a TargetRegisterInfo: Add typedef unsigned LaneBitmask and use it where apropriate; NFC
llvm-svn: 248623
2015-09-25 21:51:14 +00:00
Tom Stellard 8e0257625d MCAsmInfo: Allow targets to specify when the .section directive should be omitted
Summary:
The default behavior is to omit the .section directive for .text, .data,
and sometimes .bss, but some targets may want to omit this directive for
other sections too.

The AMDGPU backend will uses this to emit a simplified syntax for section
switches.  For example if the section directive is not omitted (current
behavior), section switches to .hsatext will be printed like this:

.section .hsatext,#alloc,#execinstr,#write

This is actually wrong, because .hsatext has some custom STT_* flags,
which MC doesn't know how to print or parse.

If the section directive is omitted (made possible by this commit),
section switches will be printed like this:

.hsatext

The motivation for this patch is to make it possible to emit sections
with custom STT_* flags without having to teach MC about all the target
specific STT_* flags.

Reviewers: rafael, grosbach

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D12423

llvm-svn: 248618
2015-09-25 21:41:14 +00:00
Matthias Braun c2d4befb54 MachineBasicBlock: Factor out common code into isReturnBlock()
llvm-svn: 248617
2015-09-25 21:25:19 +00:00
Sanjoy Das 4a39b97671 Revert two SCEV changes that caused test failures in clang.
r248606: "[SCEV] Exploit A < B => (A+K) < (B+K) when possible"
r248608: "[SCEV] Teach isLoopBackedgeGuardedByCond to exploit trip counts."
llvm-svn: 248614
2015-09-25 21:16:50 +00:00
Sanjoy Das df1635d394 [SCEV] Extract helper function from isImpliedCond; NFC
Summary:
This new helper routine will be used in a subsequent change.

Reviewers: hfinkel

Subscribers: hfinkel, sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D12949

llvm-svn: 248607
2015-09-25 19:59:52 +00:00
Sanjoy Das fdec9deb13 [SCEV] Exploit A < B => (A+K) < (B+K) when possible
Summary:

This change teaches SCEV's `isImpliedCond` two new identities:

  A u< B u< -C          =>  (A + C) u< (B + C)
  A s< B s< INT_MIN - C =>  (A + C) s< (B + C)

While these are useful on their own, they're really intended to support
D12950.

Reviewers: atrick, reames, majnemer, nlewycky, hfinkel

Subscribers: aadg, sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D12948

llvm-svn: 248606
2015-09-25 19:59:49 +00:00
James Molloy eb46641c28 [GlobalsAA] Teach GlobalsAA about nocapture
Arguments to function calls marked "nocapture" can be marked as
non-escaping. However, nocapture is defined in terms of the lifetime
of the callee, and if the callee can directly or indirectly recurse to
the caller, the semantics of nocapture are invalid.

Therefore, we eagerly discover which SCC each function belongs to,
and later can check if callee and caller of a callsite belong to
the same SCC, in which case there could be recursion.

This means that we can't be so optimistic in
getModRefInfo(ImmutableCallsite) - previously we assumed all call
arguments never aliased with an escaping global. Now we need to check,
because a global could now be passed as an argument but still not
escape.

This also solves a related conformance problem: MemCpyOptimizer can
turn non-escaping stores of globals into calls to intrinsics like
llvm.memcpy/llvm/memset. This confuses GlobalsAA, which knows the
global can't escape and so returns NoModRef when queried, when
obviously a memcpy/memset call does indeed reference and modify its
arguments.

This fixes PR24800, PR24801, and PR24802.

llvm-svn: 248576
2015-09-25 15:39:29 +00:00
Sanjoy Das b513a9fa4f [Bitcode][Asm] Teach LLVM to read and write operand bundles.
Summary:
This also adds the first set of tests for operand bundles.

The optimizer has not been audited to ensure that it does the right
thing with operand bundles.

Depends on D12456.

Reviewers: reames, chandlerc, majnemer, dexonsmith, kmod, JosephTremoulet, rnk, bogner

Subscribers: maksfb, llvm-commits

Differential Revision: http://reviews.llvm.org/D12457

llvm-svn: 248551
2015-09-24 23:34:52 +00:00
Rafael Espindola 4405d5d889 Use ELFOSABI_NONE instead of ELFOSABI_LINUX.
The doesn't seem to be a difference and ELFOSABI_NONE seems to be far more
common:

* Linux doesn't care when loading and puts ELFOSABI_NONE on core dumps.
* Gold and bfd ld produce files with ELFOSABI_NONE.
* Gold and bfd ld seems to ignore EI_OSABI other than for freebsd.
* Gas puts ELFOSABI_NONE in most .o files.

llvm-svn: 248534
2015-09-24 20:57:24 +00:00
Matt Arsenault e66621b306 AMDGPU: Add s_dcache_* instructions
llvm-svn: 248533
2015-09-24 19:52:27 +00:00
Matt Arsenault d6adfb401c AMDGPU: Add cache invalidation instructions.
These are necessary for implementing mem_fence for
OpenCL 2.0.

The VI assembler tests are disabled since it seems to be
using the wrong encoding or opcode.

llvm-svn: 248532
2015-09-24 19:52:21 +00:00
Sanjoy Das 9303c24650 [IR] Add operand bundles to CallInst and InvokeInst.
Summary:
This change teaches `CallInst`s and `InvokeInst`s to maintain a set of
operand bundles as part of its operands.  `CallInst`s and `InvokeInst`s
with operand bundles co-allocate some space before their `Use` array to
hold meta information about which of its operands are part of an operand
bundle.

The strings corresponding to the bundle tags are interned into
`LLVMContextImpl::BundleTagCache`

This change does not include any parsing / bitcode support.  That's the
next change.

Depends on D12455.

Reviewers: reames, chandlerc, majnemer, dexonsmith, kmod, JosephTremoulet, rnk, bogner

Subscribers: MatzeB, sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D12456

llvm-svn: 248527
2015-09-24 19:14:18 +00:00
Artyom Skrobov cf296444ab [ARM] Handle +t2dsp feature as an ArchExtKind in ARMTargetParser.def
Currently, the availability of DSP instructions (ACLE 6.4.7) is handled in a
hand-rolled tricky condition block in tools/clang/lib/Basic/Targets.cpp, with
a FIXME: attached.

This patch changes the handling of +t2dsp to be in line with other
architecture extensions.

Following a revert of r248152 and new review comments, this patch also includes
renaming FeatureDSPThumb2 -> FeatureDSP, hasThumb2DSP() -> hasDSP(), etc.
The spelling of "t2dsp" is preserved, pending a further investigation of its
possible external usage.

Differential Revision: http://reviews.llvm.org/D12937

llvm-svn: 248519
2015-09-24 17:31:16 +00:00
Matt Arsenault 68d938649e Introduce target hook for optimizing register copies
Allow a target to do something other than search for copies
that will avoid cross register bank copies.

Implement for SI by only rewriting the most basic copies,
so it should look through anything like a subregister extract.

I'm not entirely satisified with this because it seems like
eliminating a reg_sequence that isn't fully used should work
generically for all targets without them having to override
something. However, it seems to be tricky to have a simple
implementation of this without rewriting to invalid  kinds
of subregister copies on some targets.

I'm not sure if there is currently a generic way to easily check
if a subregister index would be valid for the current use.
The current set of TargetRegisterInfo::get*Class functions don't
quite behave like I would expect (e.g. getSubClassWithSubReg
returns the maximal register class rather than the minimal), so
I'm not sure how to make the generic test keep searching if
SrcRC:SrcSubReg is a valid replacement for DefRC:DefSubReg. Making
the default implementation to check for simple copies breaks
a variety of ARM and x86 tests by producing illegal subregister uses.

The ARM tests are not actually changed since it should still be using
the same sharesSameRegisterFile implementation, this just relaxes
them to not check for specific registers.

llvm-svn: 248478
2015-09-24 08:36:14 +00:00
Justin Bogner 49655f806f BasicAA: Move BasicAAResult::alias out-of-line. NFC
This makes the header more readable and cleans up some unnecessary
header differences between NDEBUG and !NDEBUG.

llvm-svn: 248462
2015-09-24 04:59:24 +00:00
Sanjoy Das b07fc572bd [IR] Teach `llvm::User` to co-allocate a descriptor.
Summary:
With this change, subclasses of `llvm::User` will be able to co-allocate
a variable number of bytes (called a "descriptor") with the `llvm::User`
instance.  The co-allocated descriptor can later be accessed using
`llvm::User::getDescriptor`.  This will be used in later changes to
implement operand bundles.

This change steals one bit from `NumUserOperands`, but given that it is
still 28 bits wide I don't think this will be a practical issue.

This change does not allow allocating hung off uses with descriptors.
This only for simplicity, not for any fundamental reason; and we can
easily add this functionality later if needed.

Reviewers: reames, chandlerc, dexonsmith, kmod, majnemer, pete, JosephTremoulet

Subscribers: pete, sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D12455

llvm-svn: 248453
2015-09-24 01:00:49 +00:00
Rui Ueyama 464d8eb9b7 Remove iterator_range::end.
Because the current proposal does not include that member function,
and we are trying to keep in line with that.

llvm-svn: 248451
2015-09-24 00:23:07 +00:00
Rui Ueyama ffc9b444a4 Add iterator_range::end() predicate.
llvm-svn: 248447
2015-09-23 23:58:29 +00:00
Sanjay Patel 13e8bbc237 set div/rem default values to 'expensive' in TargetTransformInfo's cost model
...because that's what the cost model was intended to do.

As discussed in D12882, this fix has a temporary unintended consequence for
SimplifyCFG: it causes us to not speculate an fdiv. However, two wrongs make
PR24818 right, and two wrongs make PR24343 act right even though it's really
still wrong.

I intend to correct SimplifyCFG and add to CodeGenPrepare to account for this
cost model change and preserve the righteousness for the bug report cases.

https://llvm.org/bugs/show_bug.cgi?id=24818
https://llvm.org/bugs/show_bug.cgi?id=24343

Differential Revision: http://reviews.llvm.org/D12882

llvm-svn: 248439
2015-09-23 22:28:18 +00:00
Philip Reames e144025652 [docs] Update DominatorTree docs to clarify expectations around unreachable blocks
Note: I'm am not trying to describe what "should be"; I'm only describing what is true today.

This came out of my recent question to llvm-dev titled: When can the dominator tree not contain a node for a basic block?

Differential Revision: http://reviews.llvm.org/D13078

llvm-svn: 248417
2015-09-23 18:39:37 +00:00