often expressed as "x >= y ? x : y", there is a good chance we can extract
the existing "x >= y" from it and use that as a replacement for "max(x,y)==x".
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but according to my super-optimizer there are only two missed simplifications
of -instsimplify kind when compiling bzip2, and this is one of them. It amuses
me to have bzip2 be perfectly optimized as far as instsimplify goes!
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This adds functionality to remove size/zero extension during indvars
without generating a canonical IV and rewriting all IV users. It's
disabled by default so should have no effect on codegen. Work in progress.
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max(a,b) >= a -> true. According to my super-optimizer, these are
by far the most common simplifications (of the -instsimplify kind)
that occur in the testsuite and aren't caught by -std-compile-opts.
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This automagically provides a transform noticed by my super-optimizer
as occurring quite often: "rem x, (select cond, x, 1)" -> 0.
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wider load would allow elimination of subsequent loads, and when the wider
load is still a native integer type. This eliminates a ton of loads on
various benchmarks involving struct fields, though it is somewhat hobbled
by clang not being very aggressive about field alignment.
This is yet another step along the way towards resolving PR6627.
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only check arguments with pointer types. Update the documentation
of IntrReadArgMem reflect this.
While here, add support for TBAA tags on intrinsic calls.
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Added a type check in ScalarEvolution::computeSCEVAtScope to handle the case in which operands of an
AddRecExpr in the current scope are folded.
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an earlier load could be widened to encompass a later load. For example,
if we see:
X = load i8* P, align 4
Y = load i8* (P+3), align 1
and we have a 32-bit native integer type, we can widen the former load
to i32 which then makes the second load redundant. GVN can't actually
do anything with this load/load relation yet, so this isn't testable, but
it is the next step to resolving PR6627, and a fairly general class of
"merge neighboring loads" missed optimizations.
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This worked untill now because stars are aligned (i.e. num of complex address elments are always 0 or 2+ and when it is 2+ at least two elements are access together)
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return it as a clobber. This allows GVN to do smart things.
Enhance GVN to be smart about the case when a small load is clobbered
by a larger overlapping load. In this case, forward the value. This
allows us to compile stuff like this:
int test(void *P) {
int tmp = *(unsigned int*)P;
return tmp+*((unsigned char*)P+1);
}
into:
_test: ## @test
movl (%rdi), %ecx
movzbl %ch, %eax
addl %ecx, %eax
ret
which has one load. We already handled the case where the smaller
load was from a must-aliased base pointer.
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Based on PR9429, but no testcase because I can't figure out how to trigger it
anymore given other changes to the relevant code.
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For example, on 32-bit architecture, don't promote all uses of the IV
to 64-bits just because one use is a 64-bit cast.
Alternate implementation of the patch by Arnaud de Grandmaison.
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SCEV may generate expressions composed of multiple pointers, which can
lead to invalid GEP expansion. Until we can teach SCEV to follow strict
pointer rules, make sure no bad GEPs creep into IR.
Fixes rdar://problem/9038671.
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memory builtins as equivalent to malloc/free.
This is different from any attribute we have. For example, you can delete the
allocators when their result is unused, but you can't collapse two calls to the
same function, even if no global/memory state has changed in between. The
noalias return states that the result does not alias any other pointer, but
instcombine optimizes malloc() as though the result is non-null for the purpose
of eliminating unused pointers.
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