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added constant folding & branch elimination to skslc
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BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2489673002

Review-Url: https://codereview.chromium.org/2489673002
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ethannicholas authored and Commit bot committed Nov 9, 2016
1 parent 6a01554 commit 6136310
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Showing 4 changed files with 227 additions and 9 deletions.
110 changes: 105 additions & 5 deletions src/sksl/SkSLIRGenerator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -246,6 +246,17 @@ std::unique_ptr<Statement> IRGenerator::convertIf(const ASTIfStatement& s) {
return nullptr;
}
}
if (test->fKind == Expression::kBoolLiteral_Kind) {
// static boolean value, fold down to a single branch
if (((BoolLiteral&) *test).fValue) {
return ifTrue;
} else if (s.fIfFalse) {
return ifFalse;
} else {
// False & no else clause. Not an error, so don't return null!
return std::unique_ptr<Statement>(new Block(s.fPosition, { }, fSymbolTable));
}
}
return std::unique_ptr<Statement>(new IfStatement(s.fPosition, std::move(test),
std::move(ifTrue), std::move(ifFalse)));
}
Expand Down Expand Up @@ -794,6 +805,78 @@ static bool determine_binary_type(const Context& context,
return false;
}

/**
* If both operands are compile-time constants and can be folded, returns an expression representing
* the folded value. Otherwise, returns null. Note that unlike most other functions here, null does
* not represent a compilation error.
*/
std::unique_ptr<Expression> IRGenerator::constantFold(const Expression& left,
Token::Kind op,
const Expression& right) {
// Note that we expressly do not worry about precision and overflow here -- we use the maximum
// precision to calculate the results and hope the result makes sense. The plan is to move the
// Skia caps into SkSL, so we have access to all of them including the precisions of the various
// types, which will let us be more intelligent about this.
if (left.fKind == Expression::kBoolLiteral_Kind &&
right.fKind == Expression::kBoolLiteral_Kind) {
bool leftVal = ((BoolLiteral&) left).fValue;
bool rightVal = ((BoolLiteral&) right).fValue;
bool result;
switch (op) {
case Token::LOGICALAND: result = leftVal && rightVal; break;
case Token::LOGICALOR: result = leftVal || rightVal; break;
case Token::LOGICALXOR: result = leftVal ^ rightVal; break;
default: return nullptr;
}
return std::unique_ptr<Expression>(new BoolLiteral(fContext, left.fPosition, result));
}
#define RESULT(t, op) std::unique_ptr<Expression>(new t ## Literal(fContext, left.fPosition, \
leftVal op rightVal))
if (left.fKind == Expression::kIntLiteral_Kind && right.fKind == Expression::kIntLiteral_Kind) {
int64_t leftVal = ((IntLiteral&) left).fValue;
int64_t rightVal = ((IntLiteral&) right).fValue;
switch (op) {
case Token::PLUS: return RESULT(Int, +);
case Token::MINUS: return RESULT(Int, -);
case Token::STAR: return RESULT(Int, *);
case Token::SLASH: return RESULT(Int, /);
case Token::PERCENT: return RESULT(Int, %);
case Token::BITWISEAND: return RESULT(Int, &);
case Token::BITWISEOR: return RESULT(Int, |);
case Token::BITWISEXOR: return RESULT(Int, ^);
case Token::SHL: return RESULT(Int, <<);
case Token::SHR: return RESULT(Int, >>);
case Token::EQEQ: return RESULT(Bool, ==);
case Token::NEQ: return RESULT(Bool, !=);
case Token::GT: return RESULT(Bool, >);
case Token::GTEQ: return RESULT(Bool, >=);
case Token::LT: return RESULT(Bool, <);
case Token::LTEQ: return RESULT(Bool, <=);
default: return nullptr;
}
}
if (left.fKind == Expression::kFloatLiteral_Kind &&
right.fKind == Expression::kFloatLiteral_Kind) {
double leftVal = ((FloatLiteral&) left).fValue;
double rightVal = ((FloatLiteral&) right).fValue;
switch (op) {
case Token::PLUS: return RESULT(Float, +);
case Token::MINUS: return RESULT(Float, -);
case Token::STAR: return RESULT(Float, *);
case Token::SLASH: return RESULT(Float, /);
case Token::EQEQ: return RESULT(Bool, ==);
case Token::NEQ: return RESULT(Bool, !=);
case Token::GT: return RESULT(Bool, >);
case Token::GTEQ: return RESULT(Bool, >=);
case Token::LT: return RESULT(Bool, <);
case Token::LTEQ: return RESULT(Bool, <=);
default: return nullptr;
}
}
#undef RESULT
return nullptr;
}

std::unique_ptr<Expression> IRGenerator::convertBinaryExpression(
const ASTBinaryExpression& expression) {
std::unique_ptr<Expression> left = this->convertExpression(*expression.fLeft);
Expand Down Expand Up @@ -823,11 +906,16 @@ std::unique_ptr<Expression> IRGenerator::convertBinaryExpression(
if (!left || !right) {
return nullptr;
}
return std::unique_ptr<Expression>(new BinaryExpression(expression.fPosition,
std::move(left),
expression.fOperator,
std::move(right),
*resultType));
std::unique_ptr<Expression> result = this->constantFold(*left.get(), expression.fOperator,
*right.get());
if (!result) {
result = std::unique_ptr<Expression>(new BinaryExpression(expression.fPosition,
std::move(left),
expression.fOperator,
std::move(right),
*resultType));
}
return result;
}

std::unique_ptr<Expression> IRGenerator::convertTernaryExpression(
Expand Down Expand Up @@ -858,6 +946,14 @@ std::unique_ptr<Expression> IRGenerator::convertTernaryExpression(
ASSERT(trueType == falseType);
ifTrue = this->coerce(std::move(ifTrue), *trueType);
ifFalse = this->coerce(std::move(ifFalse), *falseType);
if (test->fKind == Expression::kBoolLiteral_Kind) {
// static boolean test, just return one of the branches
if (((BoolLiteral&) *test).fValue) {
return ifTrue;
} else {
return ifFalse;
}
}
return std::unique_ptr<Expression>(new TernaryExpression(expression.fPosition,
std::move(test),
std::move(ifTrue),
Expand Down Expand Up @@ -1126,6 +1222,10 @@ std::unique_ptr<Expression> IRGenerator::convertPrefixExpression(
"' cannot operate on '" + base->fType.description() + "'");
return nullptr;
}
if (base->fKind == Expression::kBoolLiteral_Kind) {
return std::unique_ptr<Expression>(new BoolLiteral(fContext, base->fPosition,
!((BoolLiteral&) *base).fValue));
}
break;
case Token::BITWISENOT:
if (base->fType != *fContext.fInt_Type) {
Expand Down
5 changes: 5 additions & 0 deletions src/sksl/SkSLIRGenerator.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,11 @@ class IRGenerator {
std::unique_ptr<Statement> convertDiscard(const ASTDiscardStatement& d);
std::unique_ptr<Statement> convertDo(const ASTDoStatement& d);
std::unique_ptr<Expression> convertBinaryExpression(const ASTBinaryExpression& expression);
// Returns null if it cannot fold the expression. Note that unlike most other functions here, a
// null return does not represent a compilation error.
std::unique_ptr<Expression> constantFold(const Expression& left,
Token::Kind op,
const Expression& right);
std::unique_ptr<Extension> convertExtension(const ASTExtension& e);
std::unique_ptr<Statement> convertExpressionStatement(const ASTExpressionStatement& s);
std::unique_ptr<Statement> convertFor(const ASTForStatement& f);
Expand Down
16 changes: 16 additions & 0 deletions tests/SkSLErrorTest.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -352,3 +352,19 @@ DEF_TEST(SkSLContinueOutsideLoop, r) {
"void foo() { for(;;); continue; }",
"error: 1: continue statement must be inside a loop\n1 error\n");
}

DEF_TEST(SkSLStaticIfError, r) {
// ensure eliminated branch of static if / ternary is still checked for errors
test_failure(r,
"void foo() { if (true); else x = 5; }",
"error: 1: unknown identifier 'x'\n1 error\n");
test_failure(r,
"void foo() { if (false) x = 5; }",
"error: 1: unknown identifier 'x'\n1 error\n");
test_failure(r,
"void foo() { true ? 5 : x; }",
"error: 1: unknown identifier 'x'\n1 error\n");
test_failure(r,
"void foo() { false ? x : 5; }",
"error: 1: unknown identifier 'x'\n1 error\n");
}
105 changes: 101 additions & 4 deletions tests/SkSLGLSLTest.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,7 @@ DEF_TEST(SkSLHelloWorld, r) {
DEF_TEST(SkSLControl, r) {
test(r,
"void main() {"
"if (1 + 2 + 3 > 5) { sk_FragColor = vec4(0.75); } else { discard; }"
"if (sqrt(2) > 5) { sk_FragColor = vec4(0.75); } else { discard; }"
"int i = 0;"
"while (i < 10) sk_FragColor *= 0.5;"
"do { sk_FragColor += 0.01; } while (sk_FragColor.x < 0.7);"
Expand All @@ -55,7 +55,7 @@ DEF_TEST(SkSLControl, r) {
default_caps(),
"#version 400\n"
"void main() {\n"
" if ((1 + 2) + 3 > 5) {\n"
" if (sqrt(2.0) > 5.0) {\n"
" gl_FragColor = vec4(0.75);\n"
" } else {\n"
" discard;\n"
Expand Down Expand Up @@ -104,7 +104,7 @@ DEF_TEST(SkSLOperators, r) {
"x = x + y * z * x * (y - z);"
"y = x / y / z;"
"z = (z / 2 % 3 << 4) >> 2 << 1;"
"bool b = (x > 4) == x < 2 || 2 >= 5 && y <= z && 12 != 11;"
"bool b = (x > 4) == x < 2 || 2 >= sqrt(2) && y <= z;"
"x += 12;"
"x -= 12;"
"x *= y /= z = 10;"
Expand All @@ -126,7 +126,7 @@ DEF_TEST(SkSLOperators, r) {
" x = x + ((y * float(z)) * x) * (y - float(z));\n"
" y = (x / y) / float(z);\n"
" z = (((z / 2) % 3 << 4) >> 2) << 1;\n"
" bool b = x > 4.0 == x < 2.0 || (2 >= 5 && y <= float(z)) && 12 != 11;\n"
" bool b = x > 4.0 == x < 2.0 || 2.0 >= sqrt(2.0) && y <= float(z);\n"
" x += 12.0;\n"
" x -= 12.0;\n"
" x *= (y /= float(z = 10));\n"
Expand Down Expand Up @@ -430,3 +430,100 @@ DEF_TEST(SkSLDerivatives, r) {
" float x = dFdx(1.0);\n"
"}\n");
}

DEF_TEST(SkSLConstantFolding, r) {
test(r,
"void main() {"
"float f_add = 32 + 2;"
"float f_sub = 32 - 2;"
"float f_mul = 32 * 2;"
"float f_div = 32 / 2;"
"float mixed = (12 > 2.0) ? (10 * 2 / 5 + 18 - 3) : 0;"
"int i_add = 32 + 2;"
"int i_sub = 32 - 2;"
"int i_mul = 32 * 2;"
"int i_div = 32 / 2;"
"int i_or = 12 | 6;"
"int i_and = 254 & 7;"
"int i_xor = 2 ^ 7;"
"int i_shl = 1 << 4;"
"int i_shr = 128 >> 2;"
"bool gt_it = 6 > 5;"
"bool gt_if = 6 > 6;"
"bool gt_ft = 6.0 > 5.0;"
"bool gt_ff = 6.0 > 6.0;"
"bool gte_it = 6 >= 6;"
"bool gte_if = 6 >= 7;"
"bool gte_ft = 6.0 >= 6.0;"
"bool gte_ff = 6.0 >= 7.0;"
"bool lte_it = 6 <= 6;"
"bool lte_if = 6 <= 5;"
"bool lte_ft = 6.0 <= 6.0;"
"bool lte_ff = 6.0 <= 5.0;"
"bool or_t = 1 == 1 || 2 == 8;"
"bool or_f = 1 > 1 || 2 == 8;"
"bool and_t = 1 == 1 && 2 <= 8;"
"bool and_f = 1 == 2 && 2 == 8;"
"bool xor_t = 1 == 1 ^^ 1 != 1;"
"bool xor_f = 1 == 1 ^^ 1 == 1;"
"int ternary = 10 > 5 ? 10 : 5;"
"}",
default_caps(),
"#version 400\n"
"void main() {\n"
" float f_add = 34.0;\n"
" float f_sub = 30.0;\n"
" float f_mul = 64.0;\n"
" float f_div = 16.0;\n"
" float mixed = 19.0;\n"
" int i_add = 34;\n"
" int i_sub = 30;\n"
" int i_mul = 64;\n"
" int i_div = 16;\n"
" int i_or = 14;\n"
" int i_and = 6;\n"
" int i_xor = 5;\n"
" int i_shl = 16;\n"
" int i_shr = 32;\n"
" bool gt_it = true;\n"
" bool gt_if = false;\n"
" bool gt_ft = true;\n"
" bool gt_ff = false;\n"
" bool gte_it = true;\n"
" bool gte_if = false;\n"
" bool gte_ft = true;\n"
" bool gte_ff = false;\n"
" bool lte_it = true;\n"
" bool lte_if = false;\n"
" bool lte_ft = true;\n"
" bool lte_ff = false;\n"
" bool or_t = true;\n"
" bool or_f = false;\n"
" bool and_t = true;\n"
" bool and_f = false;\n"
" bool xor_t = true;\n"
" bool xor_f = false;\n"
" int ternary = 10;\n"
"}\n");
}

DEF_TEST(SkSLStaticIf, r) {
test(r,
"void main() {"
"int x;"
"if (true) x = 1;"
"if (2 > 1) x = 2; else x = 3;"
"if (1 > 2) x = 4; else x = 5;"
"if (false) x = 6;"
"}",
default_caps(),
"#version 400\n"
"void main() {\n"
" int x;\n"
" x = 1;\n"
" x = 2;\n"
" x = 5;\n"
" {\n"
" }\n"
"}\n");
}

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