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HLSL: force FXC to never unroll loops

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Emit the "[loop]" attribute on "for" and "while" so that FXC does not
attempt to unroll them. This is to work around an FXC bug where it fails
to unroll loops with gradient operations.

FXC ostensibly unrolls such loops because gradient operations require
uniform control flow, and loops that have varying iterations may
possibly not be uniform. Tint will eventually validate that control flow
is indeed uniform, so forcing FXC to avoid unrolling in these cases
should be fine.

Bug: tint:1112
Change-Id: I10077f8b62fbbb230a0003f3864c75a8fe0e1d18
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/69880
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
This commit is contained in:
Antonio Maiorano
2021-11-18 13:50:12 +00:00
committed by Tint LUCI CQ
parent 1704fe53f5
commit 11d09f2fe7
49 changed files with 117 additions and 110 deletions
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13
src/writer/hlsl/generator_impl.cc
View File

@@ -115,6 +115,13 @@ std::ostream& operator<<(std::ostream& s, const RegisterAndSpace& rs) {
return s;
}
const char* LoopAttribute() {
// Force loops not to be unrolled to work around FXC compilation issues when
// it attempts and fails to unroll loops when it contains gradient operations.
// https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-while
return "[loop] ";
}
} // namespace
SanitizedResult Sanitize(const Program* in,
@@ -2804,7 +2811,7 @@ bool GeneratorImpl::EmitLoop(const ast::LoopStatement* stmt) {
};
TINT_SCOPED_ASSIGNMENT(emit_continuing_, emit_continuing);
line() << "while (true) {";
line() << LoopAttribute() << "while (true) {";
{
ScopedIndent si(this);
if (!EmitStatements(stmt->body->statements)) {
@@ -2874,7 +2881,7 @@ bool GeneratorImpl::EmitForLoop(const ast::ForLoopStatement* stmt) {
};
TINT_SCOPED_ASSIGNMENT(emit_continuing_, emit_continuing);
line() << "while (true) {";
line() << LoopAttribute() << "while (true) {";
increment_indent();
TINT_DEFER({
decrement_indent();
@@ -2897,7 +2904,7 @@ bool GeneratorImpl::EmitForLoop(const ast::ForLoopStatement* stmt) {
// For-loop can be generated.
{
auto out = line();
out << "for";
out << LoopAttribute() << "for";
{
ScopedParen sp(out);

2
src/writer/hlsl/generator_impl_continue_test.cc
View File

@@ -30,7 +30,7 @@ TEST_F(HlslGeneratorImplTest_Continue, Emit_Continue) {
gen.increment_indent();
ASSERT_TRUE(gen.EmitStatement(loop)) << gen.error();
EXPECT_EQ(gen.result(), R"( while (true) {
EXPECT_EQ(gen.result(), R"( [loop] while (true) {
continue;
}
)");

28
src/writer/hlsl/generator_impl_loop_test.cc
View File

@@ -34,7 +34,7 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_Loop) {
gen.increment_indent();
ASSERT_TRUE(gen.EmitStatement(l)) << gen.error();
EXPECT_EQ(gen.result(), R"( while (true) {
EXPECT_EQ(gen.result(), R"( [loop] while (true) {
discard;
}
)");
@@ -54,7 +54,7 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_LoopWithContinuing) {
gen.increment_indent();
ASSERT_TRUE(gen.EmitStatement(l)) << gen.error();
EXPECT_EQ(gen.result(), R"( while (true) {
EXPECT_EQ(gen.result(), R"( [loop] while (true) {
discard;
{
a_statement();
@@ -88,8 +88,8 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_LoopNestedWithContinuing) {
gen.increment_indent();
ASSERT_TRUE(gen.EmitStatement(outer)) << gen.error();
EXPECT_EQ(gen.result(), R"( while (true) {
while (true) {
EXPECT_EQ(gen.result(), R"( [loop] while (true) {
[loop] while (true) {
discard;
{
a_statement();
@@ -142,7 +142,7 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_LoopWithVarUsedInContinuing) {
gen.increment_indent();
ASSERT_TRUE(gen.EmitStatement(outer)) << gen.error();
EXPECT_EQ(gen.result(), R"( while (true) {
EXPECT_EQ(gen.result(), R"( [loop] while (true) {
float lhs = 2.400000095f;
float other = 0.0f;
{
@@ -169,7 +169,7 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_ForLoop) {
ASSERT_TRUE(gen.EmitStatement(f)) << gen.error();
EXPECT_EQ(gen.result(), R"( {
for(; ; ) {
[loop] for(; ; ) {
a_statement();
}
}
@@ -193,7 +193,7 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_ForLoopWithSimpleInit) {
ASSERT_TRUE(gen.EmitStatement(f)) << gen.error();
EXPECT_EQ(gen.result(), R"( {
for(int i = 0; ; ) {
[loop] for(int i = 0; ; ) {
a_statement();
}
}
@@ -223,7 +223,7 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_ForLoopWithMultiStmtInit) {
tint_tmp = false;
}
bool b = (tint_tmp);
for(; ; ) {
[loop] for(; ; ) {
a_statement();
}
}
@@ -246,7 +246,7 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_ForLoopWithSimpleCond) {
ASSERT_TRUE(gen.EmitStatement(f)) << gen.error();
EXPECT_EQ(gen.result(), R"( {
for(; true; ) {
[loop] for(; true; ) {
a_statement();
}
}
@@ -272,7 +272,7 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_ForLoopWithMultiStmtCond) {
ASSERT_TRUE(gen.EmitStatement(f)) << gen.error();
EXPECT_EQ(gen.result(), R"( {
while (true) {
[loop] while (true) {
bool tint_tmp = true;
if (tint_tmp) {
tint_tmp = false;
@@ -302,7 +302,7 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_ForLoopWithSimpleCont) {
ASSERT_TRUE(gen.EmitStatement(f)) << gen.error();
EXPECT_EQ(gen.result(), R"( {
for(; ; i = (i + 1)) {
[loop] for(; ; i = (i + 1)) {
a_statement();
}
}
@@ -329,7 +329,7 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_ForLoopWithMultiStmtCont) {
ASSERT_TRUE(gen.EmitStatement(f)) << gen.error();
EXPECT_EQ(gen.result(), R"( {
while (true) {
[loop] while (true) {
a_statement();
bool tint_tmp = true;
if (tint_tmp) {
@@ -358,7 +358,7 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_ForLoopWithSimpleInitCondCont) {
ASSERT_TRUE(gen.EmitStatement(f)) << gen.error();
EXPECT_EQ(gen.result(), R"( {
for(int i = 0; true; i = (i + 1)) {
[loop] for(int i = 0; true; i = (i + 1)) {
a_statement();
}
}
@@ -394,7 +394,7 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_ForLoopWithMultiStmtInitCondCont) {
tint_tmp = false;
}
bool i = (tint_tmp);
while (true) {
[loop] while (true) {
bool tint_tmp_1 = true;
if (tint_tmp_1) {
tint_tmp_1 = false;