commit f7ce5e3632239522bf59702d68752003a1fb933d
author sbarati@apple.com <sbarati@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc> Fri May 31 04:31:54 2019 +0000
committer sbarati@apple.com <sbarati@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc> Fri May 31 04:31:54 2019 +0000
tree b4876de8ae7ba9c9ffef2023e411540b30e87cd9
parent ec6c4ffd3414640d27793baa06c03dc35b2a13e1

[WHLSL] Enforce variable lifetimes
https://bugs.webkit.org/show_bug.cgi?id=195794
<rdar://problem/50746293>

Reviewed by Myles C. Maxfield.

Source/WebCore:

In WHLSL, each variable has global lifetime. So returning a pointer to a
local variable is a legitimate and well specified thing to do. Each local
variable has a unique place in memory. So, for example:

```
thread int* ptr() { int local; return &local; }
thread int* ptrPtr() { return ptr(); }
```

In the above program, ptr() must always return the same value
as ptrPtr(). So, the following would print "42":
```
thread int* p = ptrPtr();
*ptr() = 42;
print(*p);
```

To implement these semantics, this patch introduces a new pass which does the
following transformations:
- It notes every variable whose address is taken in the program.
- Each such variable gets defined as a field in a struct.
- Each function which is an entry point defines this struct.
- Each non entry point takes a pointer to this struct as its final parameter.
- Each call to a non-native function is rewritten to pass a pointer to the
  struct as the last call argument.
- Each variable reference to "x", where "x" ends up in the struct, is
  modified to instead be "struct->x". We store to "struct->x" after declaring
  "x". If "x" is a function parameter, we store to "struct->x" as the first
  thing we do in the function body.

Tests: webgpu/whlsl-ensure-proper-variable-lifetime-2.html
       webgpu/whlsl-ensure-proper-variable-lifetime-3.html
       webgpu/whlsl-ensure-proper-variable-lifetime.html
       webgpu/whlsl-return-local-variable.html

* Modules/webgpu/WHLSL/AST/WHLSLAST.h:
* Modules/webgpu/WHLSL/AST/WHLSLExpression.h:
(WebCore::WHLSL::AST::Expression::Expression):
(WebCore::WHLSL::AST::Expression::isGlobalVariableReference const):
(WebCore::WHLSL::AST::Expression::origin const): Deleted.
* Modules/webgpu/WHLSL/AST/WHLSLFunctionDeclaration.h:
(WebCore::WHLSL::AST::FunctionDeclaration::origin):
* Modules/webgpu/WHLSL/AST/WHLSLGlobalVariableReference.h: Added.
(WebCore::WHLSL::AST::GlobalVariableReference::GlobalVariableReference):
(WebCore::WHLSL::AST::GlobalVariableReference::structField):
(WebCore::WHLSL::AST::GlobalVariableReference::base):
* Modules/webgpu/WHLSL/AST/WHLSLStatement.h:
(WebCore::WHLSL::AST::Statement::Statement):
(WebCore::WHLSL::AST::Statement::isStatementList const):
(WebCore::WHLSL::AST::Statement::isWhileLoop const):
* Modules/webgpu/WHLSL/AST/WHLSLStatementList.h: Added.
(WebCore::WHLSL::AST::StatementList::StatementList):
(WebCore::WHLSL::AST::StatementList::statements):
* Modules/webgpu/WHLSL/AST/WHLSLValue.h:
(WebCore::WHLSL::AST::Value::Value):
(WebCore::WHLSL::AST::Value::origin const):
* Modules/webgpu/WHLSL/AST/WHLSLVariableDeclaration.h:
(WebCore::WHLSL::AST::VariableDeclaration::VariableDeclaration):
(WebCore::WHLSL::AST::VariableDeclaration::takeInitializer):
(WebCore::WHLSL::AST::VariableDeclaration::origin const): Deleted.
* Modules/webgpu/WHLSL/AST/WHLSLVariableReference.h:
(WebCore::WHLSL::AST::VariableReference::wrap):
* Modules/webgpu/WHLSL/Metal/WHLSLFunctionWriter.cpp:
(WebCore::WHLSL::Metal::FunctionDefinitionWriter::visit):
* Modules/webgpu/WHLSL/WHLSLASTDumper.cpp:
(WebCore::WHLSL::ASTDumper::visit):
* Modules/webgpu/WHLSL/WHLSLASTDumper.h:
(WebCore::WHLSL::dumpASTNode):
(WebCore::WHLSL::dumpAST):
(WebCore::WHLSL::toString): Deleted.
* Modules/webgpu/WHLSL/WHLSLPrepare.cpp:
(WebCore::WHLSL::prepareShared):
* Modules/webgpu/WHLSL/WHLSLPreserveVariableLifetimes.cpp: Added.
(WebCore::WHLSL::EscapedVariableCollector::takeEscapedVariables):
(WebCore::WHLSL::anonymousToken):
(WebCore::WHLSL::PreserveLifetimes::PreserveLifetimes):
(WebCore::WHLSL::PreserveLifetimes::makeStructVariableReference):
(WebCore::WHLSL::preserveVariableLifetimes):
* Modules/webgpu/WHLSL/WHLSLPreserveVariableLifetimes.h: Added.
* Modules/webgpu/WHLSL/WHLSLVisitor.cpp:
(WebCore::WHLSL::Visitor::visit):
* Modules/webgpu/WHLSL/WHLSLVisitor.h:
* Sources.txt:
* WebCore.xcodeproj/project.pbxproj:

Source/WTF:

* wtf/PrintStream.h:

LayoutTests:

* webgpu/whlsl-ensure-proper-variable-lifetime-2-expected.html: Added.
* webgpu/whlsl-ensure-proper-variable-lifetime-2.html: Added.
* webgpu/whlsl-ensure-proper-variable-lifetime-3-expected.html: Added.
* webgpu/whlsl-ensure-proper-variable-lifetime-3.html: Added.
* webgpu/whlsl-ensure-proper-variable-lifetime-expected.html: Added.
* webgpu/whlsl-ensure-proper-variable-lifetime.html: Added.
* webgpu/whlsl-return-local-variable-expected.html: Added.
* webgpu/whlsl-return-local-variable.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@245945 268f45cc-cd09-0410-ab3c-d52691b4dbfc