Add "unknown" results for memdep, which mean "I don't know whether a dependence for the given instruction exists in the given block". This cleans up all the existing hacks in memdep which represent

Add "unknown" results for memdep, which mean "I don't know whether a dependence for the given instruction exists in the given block". This cleans up all the existing hacks in memdep which represent this concept by returning clobber with various unrelated instructions.

llvm-svn: 133031

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Disable the main feature of 130180, the elimination of loads that are
redundant with partially-aliasing loads.

When computing what portion of a clobbering load value is needed,
it doesn't consider p

Disable the main feature of 130180, the elimination of loads that are
redundant with partially-aliasing loads.

When computing what portion of a clobbering load value is needed,
it doesn't consider phi-translation which may have occurred
between the clobbing load and the redundant load.

llvm-svn: 132631

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When marking a block as being unanalyzable, use "Clobber" on the terminator instead of the first instruction in the block. This is a bit of a hack; "Clobber" isn't really the right marking in the fi

When marking a block as being unanalyzable, use "Clobber" on the terminator instead of the first instruction in the block. This is a bit of a hack; "Clobber" isn't really the right marking in the first place. memdep doesn't really have any way of properly expressing "unanalyzable" at the moment. Using it on the terminator is much less ambiguous than using it on an arbitrary instruction, though.

In the given testcase, the "Clobber" was pointing to a load, and GVN was incorrectly assuming that meant that the "Clobber" load overlapped the load being analyzed (when they are actually unrelated).

The included testcase tests both this commit and r132434.

Part two of rdar://9429882. (r132434 was mislabeled.)

llvm-svn: 132442

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In MemoryDependenceAnalysis::getNonLocalPointerDepFromBB, if a given block is is deemed unanalyzable (and we execute one of the "goto PredTranslationFailure" statements), make sure we don't put infor

In MemoryDependenceAnalysis::getNonLocalPointerDepFromBB, if a given block is is deemed unanalyzable (and we execute one of the "goto PredTranslationFailure" statements), make sure we don't put information about the predecessors of that block into the returned data structures; this can lead to, among other things, extraneous results (which will confuse passes using memdep). Fixes an assert in GVN compiling ruby. Part of rdar://problem/9521954 .

Testcase coming up soon.

llvm-svn: 132434

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@llvm.lifetime.begin acts as a load, not @llvm.lifetime.end.

llvm-svn: 131437

teach GVN to widen integer loads when they are overaligned, when doing an
wider load would allow elimination of subsequent loads, and when the wider
load is still a native integer type. This elimin

teach GVN to widen integer loads when they are overaligned, when doing an
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.

llvm-svn: 130390

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Enhance memdep to return clobber relation between noalias loads when
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+

Enhance memdep to return clobber relation between noalias loads when
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.

llvm-svn: 130250

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use AA::isMustAlias to simplify some calls.

llvm-svn: 130248

remove support for llvm.invariant.end from memdep. It is a
work-in-progress that is not progressing, and it has issues.

llvm-svn: 130247

Enhance MemDep: When alias analysis returns a partial alias result,
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

Enhance MemDep: When alias analysis returns a partial alias result,
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.

llvm-svn: 130180

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Give GetUnderlyingObject a TargetData, to keep it in sync
with BasicAA's DecomposeGEPExpression, which recently began
using a TargetData. This fixes PR8968, though the testcase
is awkward to reduce.

Give GetUnderlyingObject a TargetData, to keep it in sync
with BasicAA's DecomposeGEPExpression, which recently began
using a TargetData. This fixes PR8968, though the testcase
is awkward to reduce.

Also, update several off GetUnderlyingObject's users
which happen to have a TargetData handy to pass it in.

llvm-svn: 124134

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Revert r123207: "Turn on memdep's verifyRemoved() in an attempt to smoke out the cause of our gcc bootstrap miscompare."

It didn't.

llvm-svn: 123215

Turn on memdep's verifyRemoved() in an attempt to smoke out the cause of our gcc bootstrap miscompare.

llvm-svn: 123207

Change all self assignments X=X to (void)X, so that we can turn on a
new gcc warning that complains on self-assignments and
self-initializations.

llvm-svn: 122458

Move Value::getUnderlyingObject to be a standalone
function so that it can live in Analysis instead of
VMCore.

llvm-svn: 121885

Update memdep to handle PartialAlias as MayAlias.

llvm-svn: 121723

strength reduce this.

llvm-svn: 120381

Initialize MemDep's TD member so buildbots don't trip over an uninitialized pointer (TD is passed to PHITransAddr).

I wonder why this didn't explode earlier.

llvm-svn: 119944

implement PR8576, deleting dead stores with intervening may-alias stores.

llvm-svn: 119927

Add helper functions for computing the Location of load, store,
and vaarg instructions.

llvm-svn: 118845

It's not necessary to clear out the Size and TBAATag at each of
these points.

llvm-svn: 118752

Set NonLocalDepInfo's Size field to UnknownSize when invalidating
it, so that it doesn't appear to be a known size.

llvm-svn: 118748

When clearing a non-local pointer dependency cache entry, clear
the reverse map too. This fixes seflhost build errors.

llvm-svn: 118729

Factor out the code for computing an AliasAnalysis::Location
for a given instruction into a helper function.

llvm-svn: 118723

Fully invalidate cached results when a prior query's size or
type is insufficient for, or incompatible with, the current query.

llvm-svn: 118721