when it detects undefined behavior. llvm.trap generally codegens into some
thing really small (e.g. a 2 byte ud2 instruction on x86) and debugging this
sort of thing is "nontrivial". For example, we now compile:
void foo() { *(int*)0 = 42; }
into:
_foo:
pushl %ebp
movl %esp, %ebp
ud2
Some may even claim that this is a security hole, though that seems dubious
to me. This addresses rdar://7958343 - Optimizing away null dereference
potentially allows arbitrary code execution
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with a vector input and output into a shuffle vector. This sort of
sequence happens when the input code stores with one type and reloads
with another type and then SROA promotes to i96 integers, which make
everyone sad.
This fixes rdar://7896024
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LSRUse's Regs set after all pruning is done, rather than trying
to do it on the fly, which can produce an incomplete result.
This fixes a case where heuristic pruning was stripping all
formulae from a use, which led the solver to enter an infinite
loop.
Also, add a few asserts to diagnose this kind of situation.
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indirect branches in all the predecessors. This avoids unnecessarily
splitting edges in cases where load PRE is not possible anyway.
Thanks to Jakub Staszak for pointing this out.
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halting analysis, it is illegal to delete a call to a read-only function.
The correct solution is almost certainly to add a "must halt" attribute and
only allow deletions in its presence.
XFAIL the relevant testcase for now.
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that can have a big effect :). The first is to enable the
iterative SCC passmanager juice that kicks in when the
scc passmgr detects that a function pass has devirtualized
a call. In this case, it will rerun all the passes it
manages on the SCC, up to the iteration count limit (4). This
is useful because a function pass may devirualize a call, and
we want the inliner to inline it, or pruneeh to infer stuff
about it, etc.
The second patch is to add *all* call sites to the
DevirtualizedCalls list the inliner uses. This list is
about to get renamed, but the jist of this is that the
inliner now reconsiders *all* inlined call sites as candidates
for further inlining. The intuition is this that in cases
like this:
f() { g(1); } g(int x) { h(x); }
We analyze this bottom up, and may decide that it isn't
profitable to inline H into G. Next step, we decide that it is
profitable to inline G into F, and do so, which means that F
now calls H. Even though the call from G -> H may not have been
profitable to inline, the call from F -> H may be (in this case
because a constant allows folding etc).
In my spot checks, this doesn't have a big impact on code. For
example, the LLC output for 252.eon grew from 0.02% (from
317252 to 317308) and 176.gcc actually shrunk by .3% (from 1525612
to 1520964 bytes). 252.eon never iterated in the SCC Passmgr,
176.gcc iterated at most 1 time.
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that appear due to inlining a callee as candidates for
futher inlining, but a recent patch made it do this if
those call sites were indirect and became direct.
Unfortunately, in bizarre cases (see testcase) doing this
can cause us to infinitely inline mutually recursive
functions into callers not in the cycle. Fix this by
keeping track of the inline history from which callsite
inline candidates got inlined from.
This shouldn't affect any "real world" code, but is required
for a follow on patch that is coming up next.
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add a version of createLowerInvokePass that allows the client
to specify whether it wants "expensive" or "cheap" lowering.
Patch by Alex Mac!
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This fixes a bug where calls inlined into an invoke would get
changed into an invoke but the array would keep pointing to
the (now dead) call. The improved inliner behavior is still
disabled for now.
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misses an opportunity to fold add operands, but folds them
after LSR has separated them out. This fixes rdar://7886751.
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that appear in the SCC as a result of inlining as candidates
for inlining. Change this so that it *does* consider call
sites that change from being indirect to being direct as a
result of inlining. This allows it to completely
"devirtualize" the testcase.
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arguments are handled with a new InlineFunctionInfo class. This
makes it easier to extend InlineFunction to return more info in the
future.
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define void @f3(void (i8*)* %__f) ssp {
entry:
call void %__f(i8* undef)
unreachable
}
define void @f4(i8* %this) ssp align 2 {
entry:
call void @f3(void (i8*)* @f2) ssp
ret void
}
The inliner is turning the indirect call to %__f into a direct
call to F2. Make the call graph more precise when this happens.
The inliner doesn't revisit call sites introduced by inlining,
so there isn't an easy way to test for this, but a more precise
callgraph is a good thing.
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condition we're unswitching on. In this case, don't try to
simplify the second copy of the loop which may be dead or not,
but is probably a constant now. This fixes PR6879
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Arg promotion was deleting call graph nodes that still had references
from the 'indirect' CGN. Like the inliner, it should only delete the
function if all references are gone.
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just ask ScalarEvolution for it on demand. This helps IVUsers be more robust
in the case of expressions changing underneath it. This fixes PR6862.
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to determine where to place PHIs by iteratively comparing reaching definitions
at each block. That was just plain wrong. This version now computes the
dominator tree within the subset of the CFG where PHIs may need to be placed,
and then places the PHIs in the iterated dominance frontier of each definition.
The rest of the patch is mostly the same, with a few more performance
improvements added in.
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Probably the best way to know that all getOperand() calls have been handled
is to replace that API instead of updating.
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to CallGraphSCCPass's instead of passing around a
std::vector<CallGraphNode*>. No functionality change,
but now we have a much tidier interface.
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callee is expected to be expanded to something else by codegen, so that
normal infinitely recursive calls are still transformed.
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with a fix for self-hosting
rotate CallInst operands, i.e. move callee to the back
of the operand array
the motivation for this patch are laid out in my mail to llvm-commits:
more efficient access to operands and callee, faster callgraph-construction,
smaller compiler binary
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