Add scoped-noalias metadata
This commit adds scoped noalias metadata. The primary motivations for this
feature are:
1. To preserve noalias function attribute information when inlining
2. To provide the ability to model block-scope C99 restrict pointers
Neither of these two abilities are added here, only the necessary
infrastructure. In fact, there should be no change to existing functionality,
only the addition of new features. The logic that converts noalias function
parameters into this metadata during inlining will come in a follow-up commit.
What is added here is the ability to generally specify noalias memory-access
sets. Regarding the metadata, alias-analysis scopes are defined similar to TBAA
nodes:
!scope0 = metadata !{ metadata !"scope of foo()" }
!scope1 = metadata !{ metadata !"scope 1", metadata !scope0 }
!scope2 = metadata !{ metadata !"scope 2", metadata !scope0 }
!scope3 = metadata !{ metadata !"scope 2.1", metadata !scope2 }
!scope4 = metadata !{ metadata !"scope 2.2", metadata !scope2 }
Loads and stores can be tagged with an alias-analysis scope, and also, with a
noalias tag for a specific scope:
... = load %ptr1, !alias.scope !{ !scope1 }
... = load %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 }
When evaluating an aliasing query, if one of the instructions is associated
with an alias.scope id that is identical to the noalias scope associated with
the other instruction, or is a descendant (in the scope hierarchy) of the
noalias scope associated with the other instruction, then the two memory
accesses are assumed not to alias.
Note that is the first element of the scope metadata is a string, then it can
be combined accross functions and translation units. The string can be replaced
by a self-reference to create globally unqiue scope identifiers.
[Note: This overview is slightly stylized, since the metadata nodes really need
to just be numbers (!0 instead of !scope0), and the scope lists are also global
unnamed metadata.]
Existing noalias metadata in a callee is "cloned" for use by the inlined code.
This is necessary because the aliasing scopes are unique to each call site
(because of possible control dependencies on the aliasing properties). For
example, consider a function: foo(noalias a, noalias b) { *a = *b; } that gets
inlined into bar() { ... if (...) foo(a1, b1); ... if (...) foo(a2, b2); } --
now just because we know that a1 does not alias with b1 at the first call site,
and a2 does not alias with b2 at the second call site, we cannot let inlining
these functons have the metadata imply that a1 does not alias with b2.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213864 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-24 14:25:39 +00:00
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; RUN: opt < %s -basicaa -scoped-noalias -aa-eval -evaluate-aa-metadata -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
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target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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define void @foo2(float* nocapture %a, float* nocapture %b, float* nocapture readonly %c) #0 {
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entry:
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; CHECK-LABEL: Function: foo2
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2015-02-27 21:17:42 +00:00
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%0 = load float, float* %c, align 4, !alias.scope !0
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[opaque pointer type] Add textual IR support for explicit type parameter to getelementptr instruction
One of several parallel first steps to remove the target type of pointers,
replacing them with a single opaque pointer type.
This adds an explicit type parameter to the gep instruction so that when the
first parameter becomes an opaque pointer type, the type to gep through is
still available to the instructions.
* This doesn't modify gep operators, only instructions (operators will be
handled separately)
* Textual IR changes only. Bitcode (including upgrade) and changing the
in-memory representation will be in separate changes.
* geps of vectors are transformed as:
getelementptr <4 x float*> %x, ...
->getelementptr float, <4 x float*> %x, ...
Then, once the opaque pointer type is introduced, this will ultimately look
like:
getelementptr float, <4 x ptr> %x
with the unambiguous interpretation that it is a vector of pointers to float.
* address spaces remain on the pointer, not the type:
getelementptr float addrspace(1)* %x
->getelementptr float, float addrspace(1)* %x
Then, eventually:
getelementptr float, ptr addrspace(1) %x
Importantly, the massive amount of test case churn has been automated by
same crappy python code. I had to manually update a few test cases that
wouldn't fit the script's model (r228970,r229196,r229197,r229198). The
python script just massages stdin and writes the result to stdout, I
then wrapped that in a shell script to handle replacing files, then
using the usual find+xargs to migrate all the files.
update.py:
import fileinput
import sys
import re
ibrep = re.compile(r"(^.*?[^%\w]getelementptr inbounds )(((?:<\d* x )?)(.*?)(| addrspace\(\d\)) *\*(|>)(?:$| *(?:%|@|null|undef|blockaddress|getelementptr|addrspacecast|bitcast|inttoptr|\[\[[a-zA-Z]|\{\{).*$))")
normrep = re.compile( r"(^.*?[^%\w]getelementptr )(((?:<\d* x )?)(.*?)(| addrspace\(\d\)) *\*(|>)(?:$| *(?:%|@|null|undef|blockaddress|getelementptr|addrspacecast|bitcast|inttoptr|\[\[[a-zA-Z]|\{\{).*$))")
def conv(match, line):
if not match:
return line
line = match.groups()[0]
if len(match.groups()[5]) == 0:
line += match.groups()[2]
line += match.groups()[3]
line += ", "
line += match.groups()[1]
line += "\n"
return line
for line in sys.stdin:
if line.find("getelementptr ") == line.find("getelementptr inbounds"):
if line.find("getelementptr inbounds") != line.find("getelementptr inbounds ("):
line = conv(re.match(ibrep, line), line)
elif line.find("getelementptr ") != line.find("getelementptr ("):
line = conv(re.match(normrep, line), line)
sys.stdout.write(line)
apply.sh:
for name in "$@"
do
python3 `dirname "$0"`/update.py < "$name" > "$name.tmp" && mv "$name.tmp" "$name"
rm -f "$name.tmp"
done
The actual commands:
From llvm/src:
find test/ -name *.ll | xargs ./apply.sh
From llvm/src/tools/clang:
find test/ -name *.mm -o -name *.m -o -name *.cpp -o -name *.c | xargs -I '{}' ../../apply.sh "{}"
From llvm/src/tools/polly:
find test/ -name *.ll | xargs ./apply.sh
After that, check-all (with llvm, clang, clang-tools-extra, lld,
compiler-rt, and polly all checked out).
The extra 'rm' in the apply.sh script is due to a few files in clang's test
suite using interesting unicode stuff that my python script was throwing
exceptions on. None of those files needed to be migrated, so it seemed
sufficient to ignore those cases.
Reviewers: rafael, dexonsmith, grosser
Differential Revision: http://reviews.llvm.org/D7636
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230786 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-27 19:29:02 +00:00
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%arrayidx.i = getelementptr inbounds float, float* %a, i64 5
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Simplify and improve scoped-noalias metadata semantics
In the process of fixing the noalias parameter -> metadata conversion process
that will take place during inlining (which will be committed soon, but not
turned on by default), I have come to realize that the semantics provided by
yesterday's commit are not really what we want. Here's why:
void foo(noalias a, noalias b, noalias c, bool x) {
*q = x ? a : b;
*c = *q;
}
Generically, we know that *c does not alias with *a and with *b (so there is an
'and' in what we know we're not), and we know that *q might be derived from *a
or from *b (so there is an 'or' in what we know that we are). So we do not want
the semantics currently, where any noalias scope matching any alias.scope
causes a NoAlias return. What we want to know is that the noalias scopes form a
superset of the alias.scope list (meaning that all the things we know we're not
is a superset of all of things the other instruction might be).
Making that change, however, introduces a composibility problem. If we inline
once, adding the noalias metadata, and then inline again adding more, and we
append new scopes onto the noalias and alias.scope lists each time. But, this
means that we could change what was a NoAlias result previously into a MayAlias
result because we appended an additional scope onto one of the alias.scope
lists. So, instead of giving scopes the ability to have parents (which I had
borrowed from the TBAA implementation, but seems increasingly unlikely to be
useful in practice), I've given them domains. The subset/superset condition now
applies within each domain independently, and we only need it to hold in one
domain. Each time we inline, we add the new scopes in a new scope domain, and
everything now composes nicely. In addition, this simplifies the
implementation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213948 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-25 15:50:02 +00:00
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store float %0, float* %arrayidx.i, align 4, !alias.scope !5, !noalias !4
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[opaque pointer type] Add textual IR support for explicit type parameter to getelementptr instruction
One of several parallel first steps to remove the target type of pointers,
replacing them with a single opaque pointer type.
This adds an explicit type parameter to the gep instruction so that when the
first parameter becomes an opaque pointer type, the type to gep through is
still available to the instructions.
* This doesn't modify gep operators, only instructions (operators will be
handled separately)
* Textual IR changes only. Bitcode (including upgrade) and changing the
in-memory representation will be in separate changes.
* geps of vectors are transformed as:
getelementptr <4 x float*> %x, ...
->getelementptr float, <4 x float*> %x, ...
Then, once the opaque pointer type is introduced, this will ultimately look
like:
getelementptr float, <4 x ptr> %x
with the unambiguous interpretation that it is a vector of pointers to float.
* address spaces remain on the pointer, not the type:
getelementptr float addrspace(1)* %x
->getelementptr float, float addrspace(1)* %x
Then, eventually:
getelementptr float, ptr addrspace(1) %x
Importantly, the massive amount of test case churn has been automated by
same crappy python code. I had to manually update a few test cases that
wouldn't fit the script's model (r228970,r229196,r229197,r229198). The
python script just massages stdin and writes the result to stdout, I
then wrapped that in a shell script to handle replacing files, then
using the usual find+xargs to migrate all the files.
update.py:
import fileinput
import sys
import re
ibrep = re.compile(r"(^.*?[^%\w]getelementptr inbounds )(((?:<\d* x )?)(.*?)(| addrspace\(\d\)) *\*(|>)(?:$| *(?:%|@|null|undef|blockaddress|getelementptr|addrspacecast|bitcast|inttoptr|\[\[[a-zA-Z]|\{\{).*$))")
normrep = re.compile( r"(^.*?[^%\w]getelementptr )(((?:<\d* x )?)(.*?)(| addrspace\(\d\)) *\*(|>)(?:$| *(?:%|@|null|undef|blockaddress|getelementptr|addrspacecast|bitcast|inttoptr|\[\[[a-zA-Z]|\{\{).*$))")
def conv(match, line):
if not match:
return line
line = match.groups()[0]
if len(match.groups()[5]) == 0:
line += match.groups()[2]
line += match.groups()[3]
line += ", "
line += match.groups()[1]
line += "\n"
return line
for line in sys.stdin:
if line.find("getelementptr ") == line.find("getelementptr inbounds"):
if line.find("getelementptr inbounds") != line.find("getelementptr inbounds ("):
line = conv(re.match(ibrep, line), line)
elif line.find("getelementptr ") != line.find("getelementptr ("):
line = conv(re.match(normrep, line), line)
sys.stdout.write(line)
apply.sh:
for name in "$@"
do
python3 `dirname "$0"`/update.py < "$name" > "$name.tmp" && mv "$name.tmp" "$name"
rm -f "$name.tmp"
done
The actual commands:
From llvm/src:
find test/ -name *.ll | xargs ./apply.sh
From llvm/src/tools/clang:
find test/ -name *.mm -o -name *.m -o -name *.cpp -o -name *.c | xargs -I '{}' ../../apply.sh "{}"
From llvm/src/tools/polly:
find test/ -name *.ll | xargs ./apply.sh
After that, check-all (with llvm, clang, clang-tools-extra, lld,
compiler-rt, and polly all checked out).
The extra 'rm' in the apply.sh script is due to a few files in clang's test
suite using interesting unicode stuff that my python script was throwing
exceptions on. None of those files needed to be migrated, so it seemed
sufficient to ignore those cases.
Reviewers: rafael, dexonsmith, grosser
Differential Revision: http://reviews.llvm.org/D7636
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230786 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-27 19:29:02 +00:00
|
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%arrayidx1.i = getelementptr inbounds float, float* %b, i64 8
|
Simplify and improve scoped-noalias metadata semantics
In the process of fixing the noalias parameter -> metadata conversion process
that will take place during inlining (which will be committed soon, but not
turned on by default), I have come to realize that the semantics provided by
yesterday's commit are not really what we want. Here's why:
void foo(noalias a, noalias b, noalias c, bool x) {
*q = x ? a : b;
*c = *q;
}
Generically, we know that *c does not alias with *a and with *b (so there is an
'and' in what we know we're not), and we know that *q might be derived from *a
or from *b (so there is an 'or' in what we know that we are). So we do not want
the semantics currently, where any noalias scope matching any alias.scope
causes a NoAlias return. What we want to know is that the noalias scopes form a
superset of the alias.scope list (meaning that all the things we know we're not
is a superset of all of things the other instruction might be).
Making that change, however, introduces a composibility problem. If we inline
once, adding the noalias metadata, and then inline again adding more, and we
append new scopes onto the noalias and alias.scope lists each time. But, this
means that we could change what was a NoAlias result previously into a MayAlias
result because we appended an additional scope onto one of the alias.scope
lists. So, instead of giving scopes the ability to have parents (which I had
borrowed from the TBAA implementation, but seems increasingly unlikely to be
useful in practice), I've given them domains. The subset/superset condition now
applies within each domain independently, and we only need it to hold in one
domain. Each time we inline, we add the new scopes in a new scope domain, and
everything now composes nicely. In addition, this simplifies the
implementation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213948 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-25 15:50:02 +00:00
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store float %0, float* %arrayidx1.i, align 4, !alias.scope !0, !noalias !5
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2015-02-27 21:17:42 +00:00
|
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%1 = load float, float* %c, align 4
|
[opaque pointer type] Add textual IR support for explicit type parameter to getelementptr instruction
One of several parallel first steps to remove the target type of pointers,
replacing them with a single opaque pointer type.
This adds an explicit type parameter to the gep instruction so that when the
first parameter becomes an opaque pointer type, the type to gep through is
still available to the instructions.
* This doesn't modify gep operators, only instructions (operators will be
handled separately)
* Textual IR changes only. Bitcode (including upgrade) and changing the
in-memory representation will be in separate changes.
* geps of vectors are transformed as:
getelementptr <4 x float*> %x, ...
->getelementptr float, <4 x float*> %x, ...
Then, once the opaque pointer type is introduced, this will ultimately look
like:
getelementptr float, <4 x ptr> %x
with the unambiguous interpretation that it is a vector of pointers to float.
* address spaces remain on the pointer, not the type:
getelementptr float addrspace(1)* %x
->getelementptr float, float addrspace(1)* %x
Then, eventually:
getelementptr float, ptr addrspace(1) %x
Importantly, the massive amount of test case churn has been automated by
same crappy python code. I had to manually update a few test cases that
wouldn't fit the script's model (r228970,r229196,r229197,r229198). The
python script just massages stdin and writes the result to stdout, I
then wrapped that in a shell script to handle replacing files, then
using the usual find+xargs to migrate all the files.
update.py:
import fileinput
import sys
import re
ibrep = re.compile(r"(^.*?[^%\w]getelementptr inbounds )(((?:<\d* x )?)(.*?)(| addrspace\(\d\)) *\*(|>)(?:$| *(?:%|@|null|undef|blockaddress|getelementptr|addrspacecast|bitcast|inttoptr|\[\[[a-zA-Z]|\{\{).*$))")
normrep = re.compile( r"(^.*?[^%\w]getelementptr )(((?:<\d* x )?)(.*?)(| addrspace\(\d\)) *\*(|>)(?:$| *(?:%|@|null|undef|blockaddress|getelementptr|addrspacecast|bitcast|inttoptr|\[\[[a-zA-Z]|\{\{).*$))")
def conv(match, line):
if not match:
return line
line = match.groups()[0]
if len(match.groups()[5]) == 0:
line += match.groups()[2]
line += match.groups()[3]
line += ", "
line += match.groups()[1]
line += "\n"
return line
for line in sys.stdin:
if line.find("getelementptr ") == line.find("getelementptr inbounds"):
if line.find("getelementptr inbounds") != line.find("getelementptr inbounds ("):
line = conv(re.match(ibrep, line), line)
elif line.find("getelementptr ") != line.find("getelementptr ("):
line = conv(re.match(normrep, line), line)
sys.stdout.write(line)
apply.sh:
for name in "$@"
do
python3 `dirname "$0"`/update.py < "$name" > "$name.tmp" && mv "$name.tmp" "$name"
rm -f "$name.tmp"
done
The actual commands:
From llvm/src:
find test/ -name *.ll | xargs ./apply.sh
From llvm/src/tools/clang:
find test/ -name *.mm -o -name *.m -o -name *.cpp -o -name *.c | xargs -I '{}' ../../apply.sh "{}"
From llvm/src/tools/polly:
find test/ -name *.ll | xargs ./apply.sh
After that, check-all (with llvm, clang, clang-tools-extra, lld,
compiler-rt, and polly all checked out).
The extra 'rm' in the apply.sh script is due to a few files in clang's test
suite using interesting unicode stuff that my python script was throwing
exceptions on. None of those files needed to be migrated, so it seemed
sufficient to ignore those cases.
Reviewers: rafael, dexonsmith, grosser
Differential Revision: http://reviews.llvm.org/D7636
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230786 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-27 19:29:02 +00:00
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%arrayidx = getelementptr inbounds float, float* %a, i64 7
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Add scoped-noalias metadata
This commit adds scoped noalias metadata. The primary motivations for this
feature are:
1. To preserve noalias function attribute information when inlining
2. To provide the ability to model block-scope C99 restrict pointers
Neither of these two abilities are added here, only the necessary
infrastructure. In fact, there should be no change to existing functionality,
only the addition of new features. The logic that converts noalias function
parameters into this metadata during inlining will come in a follow-up commit.
What is added here is the ability to generally specify noalias memory-access
sets. Regarding the metadata, alias-analysis scopes are defined similar to TBAA
nodes:
!scope0 = metadata !{ metadata !"scope of foo()" }
!scope1 = metadata !{ metadata !"scope 1", metadata !scope0 }
!scope2 = metadata !{ metadata !"scope 2", metadata !scope0 }
!scope3 = metadata !{ metadata !"scope 2.1", metadata !scope2 }
!scope4 = metadata !{ metadata !"scope 2.2", metadata !scope2 }
Loads and stores can be tagged with an alias-analysis scope, and also, with a
noalias tag for a specific scope:
... = load %ptr1, !alias.scope !{ !scope1 }
... = load %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 }
When evaluating an aliasing query, if one of the instructions is associated
with an alias.scope id that is identical to the noalias scope associated with
the other instruction, or is a descendant (in the scope hierarchy) of the
noalias scope associated with the other instruction, then the two memory
accesses are assumed not to alias.
Note that is the first element of the scope metadata is a string, then it can
be combined accross functions and translation units. The string can be replaced
by a self-reference to create globally unqiue scope identifiers.
[Note: This overview is slightly stylized, since the metadata nodes really need
to just be numbers (!0 instead of !scope0), and the scope lists are also global
unnamed metadata.]
Existing noalias metadata in a callee is "cloned" for use by the inlined code.
This is necessary because the aliasing scopes are unique to each call site
(because of possible control dependencies on the aliasing properties). For
example, consider a function: foo(noalias a, noalias b) { *a = *b; } that gets
inlined into bar() { ... if (...) foo(a1, b1); ... if (...) foo(a2, b2); } --
now just because we know that a1 does not alias with b1 at the first call site,
and a2 does not alias with b2 at the second call site, we cannot let inlining
these functons have the metadata imply that a1 does not alias with b2.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213864 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-24 14:25:39 +00:00
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store float %1, float* %arrayidx, align 4
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ret void
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2015-02-27 21:17:42 +00:00
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; CHECK: MayAlias: %0 = load float, float* %c, align 4, !alias.scope !0 <-> store float %0, float* %arrayidx.i, align 4, !alias.scope !4, !noalia
|
Simplify and improve scoped-noalias metadata semantics
In the process of fixing the noalias parameter -> metadata conversion process
that will take place during inlining (which will be committed soon, but not
turned on by default), I have come to realize that the semantics provided by
yesterday's commit are not really what we want. Here's why:
void foo(noalias a, noalias b, noalias c, bool x) {
*q = x ? a : b;
*c = *q;
}
Generically, we know that *c does not alias with *a and with *b (so there is an
'and' in what we know we're not), and we know that *q might be derived from *a
or from *b (so there is an 'or' in what we know that we are). So we do not want
the semantics currently, where any noalias scope matching any alias.scope
causes a NoAlias return. What we want to know is that the noalias scopes form a
superset of the alias.scope list (meaning that all the things we know we're not
is a superset of all of things the other instruction might be).
Making that change, however, introduces a composibility problem. If we inline
once, adding the noalias metadata, and then inline again adding more, and we
append new scopes onto the noalias and alias.scope lists each time. But, this
means that we could change what was a NoAlias result previously into a MayAlias
result because we appended an additional scope onto one of the alias.scope
lists. So, instead of giving scopes the ability to have parents (which I had
borrowed from the TBAA implementation, but seems increasingly unlikely to be
useful in practice), I've given them domains. The subset/superset condition now
applies within each domain independently, and we only need it to hold in one
domain. Each time we inline, we add the new scopes in a new scope domain, and
everything now composes nicely. In addition, this simplifies the
implementation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213948 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-25 15:50:02 +00:00
|
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|
; CHECK: s !5
|
2015-02-27 21:17:42 +00:00
|
|
|
; CHECK: MayAlias: %0 = load float, float* %c, align 4, !alias.scope !0 <-> store float %0, float* %arrayidx1.i, align 4, !alias.scope !0, !noali
|
Simplify and improve scoped-noalias metadata semantics
In the process of fixing the noalias parameter -> metadata conversion process
that will take place during inlining (which will be committed soon, but not
turned on by default), I have come to realize that the semantics provided by
yesterday's commit are not really what we want. Here's why:
void foo(noalias a, noalias b, noalias c, bool x) {
*q = x ? a : b;
*c = *q;
}
Generically, we know that *c does not alias with *a and with *b (so there is an
'and' in what we know we're not), and we know that *q might be derived from *a
or from *b (so there is an 'or' in what we know that we are). So we do not want
the semantics currently, where any noalias scope matching any alias.scope
causes a NoAlias return. What we want to know is that the noalias scopes form a
superset of the alias.scope list (meaning that all the things we know we're not
is a superset of all of things the other instruction might be).
Making that change, however, introduces a composibility problem. If we inline
once, adding the noalias metadata, and then inline again adding more, and we
append new scopes onto the noalias and alias.scope lists each time. But, this
means that we could change what was a NoAlias result previously into a MayAlias
result because we appended an additional scope onto one of the alias.scope
lists. So, instead of giving scopes the ability to have parents (which I had
borrowed from the TBAA implementation, but seems increasingly unlikely to be
useful in practice), I've given them domains. The subset/superset condition now
applies within each domain independently, and we only need it to hold in one
domain. Each time we inline, we add the new scopes in a new scope domain, and
everything now composes nicely. In addition, this simplifies the
implementation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213948 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-25 15:50:02 +00:00
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; CHECK: as !4
|
2015-02-27 21:17:42 +00:00
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; CHECK: MayAlias: %0 = load float, float* %c, align 4, !alias.scope !0 <-> store float %1, float* %arrayidx, align 4
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; CHECK: MayAlias: %1 = load float, float* %c, align 4 <-> store float %0, float* %arrayidx.i, align 4, !alias.scope !4, !noalias !5
|
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; CHECK: MayAlias: %1 = load float, float* %c, align 4 <-> store float %0, float* %arrayidx1.i, align 4, !alias.scope !0, !noalias !4
|
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; CHECK: MayAlias: %1 = load float, float* %c, align 4 <-> store float %1, float* %arrayidx, align 4
|
Simplify and improve scoped-noalias metadata semantics
In the process of fixing the noalias parameter -> metadata conversion process
that will take place during inlining (which will be committed soon, but not
turned on by default), I have come to realize that the semantics provided by
yesterday's commit are not really what we want. Here's why:
void foo(noalias a, noalias b, noalias c, bool x) {
*q = x ? a : b;
*c = *q;
}
Generically, we know that *c does not alias with *a and with *b (so there is an
'and' in what we know we're not), and we know that *q might be derived from *a
or from *b (so there is an 'or' in what we know that we are). So we do not want
the semantics currently, where any noalias scope matching any alias.scope
causes a NoAlias return. What we want to know is that the noalias scopes form a
superset of the alias.scope list (meaning that all the things we know we're not
is a superset of all of things the other instruction might be).
Making that change, however, introduces a composibility problem. If we inline
once, adding the noalias metadata, and then inline again adding more, and we
append new scopes onto the noalias and alias.scope lists each time. But, this
means that we could change what was a NoAlias result previously into a MayAlias
result because we appended an additional scope onto one of the alias.scope
lists. So, instead of giving scopes the ability to have parents (which I had
borrowed from the TBAA implementation, but seems increasingly unlikely to be
useful in practice), I've given them domains. The subset/superset condition now
applies within each domain independently, and we only need it to hold in one
domain. Each time we inline, we add the new scopes in a new scope domain, and
everything now composes nicely. In addition, this simplifies the
implementation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213948 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-25 15:50:02 +00:00
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; CHECK: NoAlias: store float %0, float* %arrayidx1.i, align 4, !alias.scope !0, !noalias !4 <-> store float %0, float* %arrayidx.i, align
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; CHECK: 4, !alias.scope !4, !noalias !5
|
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; CHECK: NoAlias: store float %1, float* %arrayidx, align 4 <-> store float %0, float* %arrayidx.i, align 4, !alias.scope !4, !noalias !5
|
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; CHECK: MayAlias: store float %1, float* %arrayidx, align 4 <-> store float %0, float* %arrayidx1.i, align 4, !alias.scope !0, !noalias !
|
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; CHECK: 4
|
Add scoped-noalias metadata
This commit adds scoped noalias metadata. The primary motivations for this
feature are:
1. To preserve noalias function attribute information when inlining
2. To provide the ability to model block-scope C99 restrict pointers
Neither of these two abilities are added here, only the necessary
infrastructure. In fact, there should be no change to existing functionality,
only the addition of new features. The logic that converts noalias function
parameters into this metadata during inlining will come in a follow-up commit.
What is added here is the ability to generally specify noalias memory-access
sets. Regarding the metadata, alias-analysis scopes are defined similar to TBAA
nodes:
!scope0 = metadata !{ metadata !"scope of foo()" }
!scope1 = metadata !{ metadata !"scope 1", metadata !scope0 }
!scope2 = metadata !{ metadata !"scope 2", metadata !scope0 }
!scope3 = metadata !{ metadata !"scope 2.1", metadata !scope2 }
!scope4 = metadata !{ metadata !"scope 2.2", metadata !scope2 }
Loads and stores can be tagged with an alias-analysis scope, and also, with a
noalias tag for a specific scope:
... = load %ptr1, !alias.scope !{ !scope1 }
... = load %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 }
When evaluating an aliasing query, if one of the instructions is associated
with an alias.scope id that is identical to the noalias scope associated with
the other instruction, or is a descendant (in the scope hierarchy) of the
noalias scope associated with the other instruction, then the two memory
accesses are assumed not to alias.
Note that is the first element of the scope metadata is a string, then it can
be combined accross functions and translation units. The string can be replaced
by a self-reference to create globally unqiue scope identifiers.
[Note: This overview is slightly stylized, since the metadata nodes really need
to just be numbers (!0 instead of !scope0), and the scope lists are also global
unnamed metadata.]
Existing noalias metadata in a callee is "cloned" for use by the inlined code.
This is necessary because the aliasing scopes are unique to each call site
(because of possible control dependencies on the aliasing properties). For
example, consider a function: foo(noalias a, noalias b) { *a = *b; } that gets
inlined into bar() { ... if (...) foo(a1, b1); ... if (...) foo(a2, b2); } --
now just because we know that a1 does not alias with b1 at the first call site,
and a2 does not alias with b2 at the second call site, we cannot let inlining
these functons have the metadata imply that a1 does not alias with b2.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213864 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-24 14:25:39 +00:00
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}
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attributes #0 = { nounwind uwtable }
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IR: Make metadata typeless in assembly
Now that `Metadata` is typeless, reflect that in the assembly. These
are the matching assembly changes for the metadata/value split in
r223802.
- Only use the `metadata` type when referencing metadata from a call
intrinsic -- i.e., only when it's used as a `Value`.
- Stop pretending that `ValueAsMetadata` is wrapped in an `MDNode`
when referencing it from call intrinsics.
So, assembly like this:
define @foo(i32 %v) {
call void @llvm.foo(metadata !{i32 %v}, metadata !0)
call void @llvm.foo(metadata !{i32 7}, metadata !0)
call void @llvm.foo(metadata !1, metadata !0)
call void @llvm.foo(metadata !3, metadata !0)
call void @llvm.foo(metadata !{metadata !3}, metadata !0)
ret void, !bar !2
}
!0 = metadata !{metadata !2}
!1 = metadata !{i32* @global}
!2 = metadata !{metadata !3}
!3 = metadata !{}
turns into this:
define @foo(i32 %v) {
call void @llvm.foo(metadata i32 %v, metadata !0)
call void @llvm.foo(metadata i32 7, metadata !0)
call void @llvm.foo(metadata i32* @global, metadata !0)
call void @llvm.foo(metadata !3, metadata !0)
call void @llvm.foo(metadata !{!3}, metadata !0)
ret void, !bar !2
}
!0 = !{!2}
!1 = !{i32* @global}
!2 = !{!3}
!3 = !{}
I wrote an upgrade script that handled almost all of the tests in llvm
and many of the tests in cfe (even handling many `CHECK` lines). I've
attached it (or will attach it in a moment if you're speedy) to PR21532
to help everyone update their out-of-tree testcases.
This is part of PR21532.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224257 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-15 19:07:53 +00:00
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!0 = !{!1, !3}
|
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|
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|
!1 = !{!1, !2, !"some scope"}
|
|
|
|
|
!2 = !{!2, !"some domain"}
|
|
|
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|
!3 = !{!3, !2, !"some other scope"}
|
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!4 = !{!1}
|
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!5 = !{!3}
|
Add scoped-noalias metadata
This commit adds scoped noalias metadata. The primary motivations for this
feature are:
1. To preserve noalias function attribute information when inlining
2. To provide the ability to model block-scope C99 restrict pointers
Neither of these two abilities are added here, only the necessary
infrastructure. In fact, there should be no change to existing functionality,
only the addition of new features. The logic that converts noalias function
parameters into this metadata during inlining will come in a follow-up commit.
What is added here is the ability to generally specify noalias memory-access
sets. Regarding the metadata, alias-analysis scopes are defined similar to TBAA
nodes:
!scope0 = metadata !{ metadata !"scope of foo()" }
!scope1 = metadata !{ metadata !"scope 1", metadata !scope0 }
!scope2 = metadata !{ metadata !"scope 2", metadata !scope0 }
!scope3 = metadata !{ metadata !"scope 2.1", metadata !scope2 }
!scope4 = metadata !{ metadata !"scope 2.2", metadata !scope2 }
Loads and stores can be tagged with an alias-analysis scope, and also, with a
noalias tag for a specific scope:
... = load %ptr1, !alias.scope !{ !scope1 }
... = load %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 }
When evaluating an aliasing query, if one of the instructions is associated
with an alias.scope id that is identical to the noalias scope associated with
the other instruction, or is a descendant (in the scope hierarchy) of the
noalias scope associated with the other instruction, then the two memory
accesses are assumed not to alias.
Note that is the first element of the scope metadata is a string, then it can
be combined accross functions and translation units. The string can be replaced
by a self-reference to create globally unqiue scope identifiers.
[Note: This overview is slightly stylized, since the metadata nodes really need
to just be numbers (!0 instead of !scope0), and the scope lists are also global
unnamed metadata.]
Existing noalias metadata in a callee is "cloned" for use by the inlined code.
This is necessary because the aliasing scopes are unique to each call site
(because of possible control dependencies on the aliasing properties). For
example, consider a function: foo(noalias a, noalias b) { *a = *b; } that gets
inlined into bar() { ... if (...) foo(a1, b1); ... if (...) foo(a2, b2); } --
now just because we know that a1 does not alias with b1 at the first call site,
and a2 does not alias with b2 at the second call site, we cannot let inlining
these functons have the metadata imply that a1 does not alias with b2.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213864 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-24 14:25:39 +00:00
|
|
|
|