Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Revert the PR#2804 handling specials input of fract(x) #2826

Merged
merged 1 commit into from
Nov 21, 2023
Merged

Revert the PR#2804 handling specials input of fract(x) #2826

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
37 changes: 2 additions & 35 deletions llpc/translator/lib/SPIRV/SPIRVReader.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -8808,42 +8808,9 @@ Value *SPIRVToLLVM::transGLSLExtInst(SPIRVExtInst *extInst, BasicBlock *bb) {
// Round up to whole number
return getBuilder()->CreateUnaryIntrinsic(Intrinsic::ceil, args[0]);

case GLSLstd450Fract: {
case GLSLstd450Fract:
// Get fractional part
auto fract = getBuilder()->CreateFract(args[0]);

// NOTE: Although SPIR-V spec says nothing about such cases: fract(-0.0), fract(+INF), fract(-INF), OpenCL spec does
// have following definitions:
//
// fract(-0.0) = -0.0
// fract(+INF) = +0.0
// fract(-INF) = -0.0
//
// When we follow it, we have two issues that are similar to modf(x):
//
// 1. When we input x=+INF/-INF to above formula, we finally get the computation of (-INF) + INF or INF - INF.
// The result is NaN returned by HW.
// 2. When we input x=-0.0 to above formula, we finally get the addition of (-0.0) + 0.0. The result is +0.0
// returned by HW.
//
// Hence, we have to manually check those special cases:
//
// y = fract(x)
// y = x == -0.0 || x == INF ? copysign(0.0, x) : y, when either NSZ or NoInfs is not present
unsigned checkFlags = 0;
if (!getBuilder()->getFastMathFlags().noSignedZeros())
checkFlags |= lgc::Builder::CmpClass::NegativeZero;
if (!getBuilder()->getFastMathFlags().noInfs())
checkFlags |= (lgc::Builder::CmpClass::NegativeZero | lgc::Builder::CmpClass::NegativeZero);

if (checkFlags) {
Value *isNegZeroOrInf = getBuilder()->createIsFPClass(args[0], checkFlags);
Value *signedZero = getBuilder()->CreateCopySign(ConstantFP::getNullValue(args[0]->getType()), args[0]);
fract = getBuilder()->CreateSelect(isNegZeroOrInf, signedZero, fract);
}

return fract;
}
return getBuilder()->CreateFract(args[0]);

case GLSLstd450Radians:
// Convert from degrees to radians
Expand Down
Loading