Skip to content

std.math.trigonometry: fix tan asm x86 implementation for ldc compiler #8199

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

Merged
RazvanN7 merged 1 commit into from
Aug 24, 2021
Merged

std.math.trigonometry: fix tan asm x86 implementation for ldc compiler #8199

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
28 changes: 16 additions & 12 deletions std/math/trigonometry.d
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -209,6 +209,12 @@ float tan(float x) @safe pure nothrow @nogc { return __ctfe ? cast(float) tan(ca
version (InlineAsm_X87)
private real tanAsm(real x) @trusted pure nothrow @nogc
{
// Separating `return real.nan` from the asm block on LDC produces unintended
// behaviour as additional instructions are generated, invalidating the asm
// logic inside the previous block. To circumvent this, we can push rnan
// manually by creating an immutable variable in the stack.
immutable rnan = real.nan;

version (X86)
{
asm pure nothrow @nogc
Expand Down Expand Up @@ -237,14 +243,13 @@ SC17: fprem1 ;
trigerr:
jnp Lret ; // if theta is NAN, return theta
fstp ST(0) ; // dump theta
}
return real.nan;

Clear1: asm pure nothrow @nogc{
fld rnan ; // return rnan
Copy link
Contributor

@kinke kinke Aug 20, 2021

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

How is this supposed to work? You're pushing rnan, then popping it immediately again via fstp in Clear1 before returning, right?

Copy link
Member Author

@ljmf00 ljmf00 Aug 20, 2021

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Ups, forgot to jump to Lret label. Nice catch, even though, it doesn't fail. Fixed

jmp Lret ;
Clear1:
fstp ST(0) ; // dump X, which is always 1
Lret:
;
}

Lret: {}
}
else version (X86_64)
{
Expand Down Expand Up @@ -288,14 +293,13 @@ trigerr:
test AH,4 ;
jz Lret ; // if theta is NAN, return theta
fstp ST(0) ; // dump theta
}
return real.nan;

Clear1: asm pure nothrow @nogc{
fld rnan ; // return rnan
jmp Lret ;
Clear1:
fstp ST(0) ; // dump X, which is always 1
Lret:
;
}

Lret: {}
}
else
static assert(0);
Expand Down