over a phi node by applying it to each operand may be wrong if the
operation and the phi node are mutually interdependent (the testcase
has a simple example of this). So only do this transform if it would
be correct to perform the operation in each predecessor of the block
containing the phi, i.e. if the other operands all dominate the phi.
This should fix the FFMPEG snow.c regression reported by İsmail Dönmez.
llvm-svn: 119347
offload the work to hasConstantValue rather than do something more
complicated (such handling mutually recursive phis) because (1) it is
not clear it is worth it; and (2) if it is worth it, maybe such logic
would be better placed in hasConstantValue. Adjust some GVN tests
which are now cleaned up much further (eg: all phi nodes are removed).
llvm-svn: 119043
operands are the phi node itself or undef, then return undef.
This logic already existed at a higher level so in practice it
shouldn't make the slightest difference. Note that this code
could be replaced by a call to PN->hasConstantValue(). However
since we bail out the moment we see a non-constant operand, it
is more efficient to have a specialized version of that logic.
llvm-svn: 119041
references. For example, this allows gvn to eliminate the load in
this example:
void foo(int n, int* p, int *q) {
p[0] = 0;
p[1] = 1;
if (n) {
*q = p[0];
}
}
llvm-svn: 118714
nodes can be used in loops, this could result in infinite looping
if there is no recursion limit, so add such a limit. It is also
used for the SelectInst case because in theory there could be an
infinite loop there too if the basic block is unreachable.
llvm-svn: 118694
The simplifications performed here never create new instructions, they
only return existing instructions (or a constant), and so are always a
win. In theory they should transform (for example)
%z = and i32 %x, %y
%s = select i1 %cond, i32 %y, i32 %z
%r = and i32 %x, %s
into
%r = and i32 %x, y
but in practice they get into a fight with instcombine, and lose.
Unfortunately instcombine does a poor job in this case. Nonetheless
I'm committing this transform to make it easier to discuss what to
do to make peace with instcombine.
llvm-svn: 118679
to optionally look for constant or local (alloca) memory.
Teach BasicAliasAnalysis::pointsToConstantMemory to look through Select
and Phi nodes, and to support looking for local memory.
Remove FunctionAttrs' PointsToLocalOrConstantMemory function, now that
AliasAnalysis knows all the tricks that it knew.
llvm-svn: 118412
of a select instruction, see if doing the compare with the
true and false values of the select gives the same result.
If so, that can be used as the value of the comparison.
llvm-svn: 118378
To create debugging information for a pointer, using DIBUilder front-end just needs
DBuilder.CreatePointerType(Ty, Size);
instead of
DebugFactory.CreateDerivedType(llvm::dwarf::DW_TAG_pointer_type,
TheCU, "", getOrCreateMainFile(),
0, Size, 0, 0, 0, OCTy);
llvm-svn: 118248
