This is how it ignores the dead code:
1) When a dead branch target, say block B, is identified, all the
blocks dominated by B is dead as well.
2) The PHIs of those blocks in dominance-frontier(B) is updated such
that the operands corresponding to dead predecessors are replaced
by "UndefVal".
Using lattice's jargon, the "UndefVal" is the "Top" in essence.
Phi node like this "phi(v1 bb1, undef xx)" will be optimized into
"v1" if v1 is constant, or v1 is an instruction which dominate this
PHI node.
3) When analyzing the availability of a load L, all dead mem-ops which
L depends on disguise as a load which evaluate exactly same value as L.
4) The dead mem-ops will be materialized as "UndefVal" during code motion.
llvm-svn: 191017
Various Windows SDK headers use _MSC_VER values to figure out what
version of the VC++ headers they're using, in particular for SAL macros.
Patch by Paul Hampson!
llvm-svn: 191015
Adds a flag to the MemorySanitizer pass that enables runtime rewriting of
indirect calls. This is part of MSanDR implementation and is needed to return
control to the DynamiRio-based helper tool on transition between instrumented
and non-instrumented modules. Disabled by default.
llvm-svn: 191006
When selecting the DAG (add (WrapperRIP ...), (FrameIndex ...)), X86 code had
spotted the FrameIndex possibility and was working out whether it could fold
the WrapperRIP into this.
The test for forming a %rip version is notionally whether we already have a
base or index register (%rip precludes both), but we were forgetting to account
for the register that would be inserted later to access the frame.
rdar://problem/15024520
llvm-svn: 190995
This puts all the global PassManager debugging flags, like
-print-after-all and -time-passes, behind a managed static. This
eliminates their static initializers and, more importantly, exit-time
destructors.
The only behavioral change I anticipate is that tools need to
initialize the PassManager before parsing the command line in order to
export these options, which makes sense. Tools that already initialize
the standard passes (opt/llc) don't need to do anything new.
llvm-svn: 190974
1) make sure that the first two instructions of the sequence cannot
separate from each other. The linker requires that they be sequential.
If they get separated, it can still work but it will not work in all
cases because the first of the instructions mostly involves the hi part
of the pc relative offset and that part changes slowly. You would have
to be at the right boundary for this to matter.
2) make sure that this sequence begins on a longword boundary.
There appears to be a bug in binutils which makes some of these calculations
get messed up if the instruction sequence does not begin on a longword
boundary. This is being investigated with the appropriate binutils folks.
llvm-svn: 190966
Use the DIVariable::isIndirect() flag set by the frontend instead of
guessing whether to set the machine location's indirection bit.
Paired commit with CFE.
llvm-svn: 190961
advertised - but it does have the caveat that calls to DynamicLibrary::AddSymbol will
"reset" if you shutdown llvm and try to come back for seconds. This is a subtle
behavior change, but I'm assuming that nobody is affected by it.
llvm-svn: 190946
XCore target: Add XCoreTargetTransformInfo
This is where getNumberOfRegisters() resides, which in turn returns the
number of vector registers (=0).
llvm-svn: 190936
For some reason I never got around to adding these at the same time as
the signed versions. No idea why.
I'm not sure whether this SystemZII::BranchC* stuff is useful, or whether
it should just be replaced with an "is normal" flag. I'll leave that
for later though.
There are some boundary conditions that can be tweaked, such as preferring
unsigned comparisons for equality with [128, 256), and "<= 255" over "< 256",
but again I'll leave those for a separate patch.
llvm-svn: 190930
advertised - but it does have the caveat that calls to DynamicLibrary::AddSymbol will
"reset" if you shutdown llvm and try to come back for seconds. This is a subtle
behavior change, but I'm assuming that nobody is affected by it.
llvm-svn: 190921
Summary:
We indicate that the object files are safe by emitting a @feat.00
absolute address symbol. The address is presumably interpreted as a
bitfield of features that the compiler would like to enable. Bit 0 is
documented in the PE COFF spec to opt in to "registered SEH", which is
what /safeseh enables.
LLVM's object files are safe by default because LLVM doesn't know how to
produce SEH handlers.
Reviewers: Bigcheese
CC: llvm-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D1691
llvm-svn: 190898
In particular, this means we emit non-external symbols defined to
variables, such as aliases or absolute addresses.
This is needed to implement /safeseh, and it appears there was some
confusion about what symbols to emit previously.
llvm-svn: 190888
Some of this code is no longer necessary since int<->ptr casts are no
longer occur as of r187444.
This also fixes handling vectors of pointers, and adds a bunch of new
testcases for vectors and address spaces.
llvm-svn: 190885
