calls into a function and if the calls bring in arrays, try to merge
them together to reduce stack size. For example, in the testcase
we'd previously end up with 4 allocas, now we end up with 2 allocas.
As described in the comments, this is not really the ideal solution
to this problem, but it is surprisingly effective. For example, on
176.gcc, we end up eliminating 67 arrays at "gccas" time and another
24 at "llvm-ld" time.
One piece of concern that I didn't look into: at -O0 -g with
forced inlining this will almost certainly result in worse debug
info. I think this is acceptable though given that this is a case
of "debugging optimized code", and we don't want debug info to
prevent the optimizer from doing things anyway.
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sinking code, since they are special. If the loop preheader happens
to be the entry block of a function, don't sink static allocas
out of it. This fixes PR4775.
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This change speeds up llvm-gcc by more then 6% at "-O0 -g" (measured by compiling InstructionCombining.cpp!)
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array member of a struct, it's possible to land in an arbitrary position
inside that struct, such that attempting to find further getelementptr
indices will fail. In such cases, folding cannot be done.
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static extents of the static array type, it causes GlobalOpt and
other passes to be more conservative. This canonicalization also
allows the constant folder to add "inbounds" to GEPs.
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TargetData is not present. It still uses TargetData when available.
This generalization also fixed some limitations in the TargetData
case; the attached testcase covers this.
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unfoldable references to a PHI node in the block being folded, and disable
the transformation in that case. The correct transformation of such PHI
nodes depends on whether BB dominates Succ, and dominance is expensive
to compute here. (Alternatively, it's possible to check whether any
uses are live, but that's also essentially a dominance calculation.
Another alternative is to use reg2mem, but it probably isn't a good idea to
use that in simplifycfg.)
Also, remove some incorrect code from CanPropagatePredecessorsForPHIs
which is made unnecessary with this patch: it didn't consider the case
where a PHI node in BB has multiple uses.
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the new load by the old load instead of by the extract element because
a store could have occurred between the load and extract element.
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few places in InstCombine to use it, to fix problems handling pointer
types. This fixes the recent llvm-gcc bootstrap error.
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also apply to vectors. This allows us to compile this:
#include <emmintrin.h>
__m128i a(__m128 a, __m128 b) { return a==a & b==b; }
__m128i b(__m128 a, __m128 b) { return a!=a | b!=b; }
to:
_a:
cmpordps %xmm1, %xmm0
ret
_b:
cmpunordps %xmm1, %xmm0
ret
with clang instead of to a ton of horrible code.
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with negative tests: this test wasn't checking what it thought it was
because it was grepping .bc, not .ll.
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Getelementptrs that are defined to wrap are virtually useless to
optimization, and getelementptrs that are undefined on any kind
of overflow are too restrictive -- it's difficult to ensure that
all intermediate addresses are within bounds. I'm going to take
a different approach.
Remove a few optimizations that depended on this flag.
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insertelement/extractelement.
I'm not entirely sure this is precisely what we want to do: should we
prefer bitcast(insertelement) or insertelement(bitcast)? Similarly. should we
prefer extractelement(bitcast) or bitcast(extractelement)?
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