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nak: Fix fneg to do fadd(-0, x)

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Thanks to floating point sillyness, fadd(0, x) isn't a no-op but
fadd(-0, x) is.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24998>
This commit is contained in:
Faith Ekstrand
2023-10-10 13:20:44 -05:00
committed by Marge Bot
parent 2c1cc06d03
commit a43e6addca
3 changed files with 20 additions and 4 deletions
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2
src/nouveau/compiler/nak_from_nir.rs
View File

@@ -360,7 +360,7 @@ impl<'a> ShaderFromNir<'a> {
let (x, y) = match alu.op {
nir_op_fabs => (srcs[0].fabs(), Src::new_zero()),
nir_op_fadd => (srcs[0], srcs[1]),
nir_op_fneg => (srcs[0].fneg(), Src::new_zero()),
nir_op_fneg => (Src::new_zero().fneg(), srcs[0].fneg()),
_ => panic!("Unhandled case"),
};
assert!(alu.def.bit_size() == 32);

18
src/nouveau/compiler/nak_ir.rs
View File

@@ -1088,7 +1088,23 @@ impl Src {
pub fn is_zero(&self) -> bool {
match self.src_ref {
SrcRef::Zero => true,
SrcRef::Zero | SrcRef::Imm32(0) => match self.src_mod {
SrcMod::None | SrcMod::FAbs | SrcMod::INeg => true,
SrcMod::FNeg | SrcMod::FNegAbs | SrcMod::BNot => false,
},
_ => false,
}
}
pub fn is_fneg_zero(&self, src_type: SrcType) -> bool {
match self.src_ref {
SrcRef::Zero | SrcRef::Imm32(0) => match self.src_mod {
SrcMod::FNeg | SrcMod::FNegAbs => true,
_ => false,
}
SrcRef::Imm32(0x80000000) => {
src_type == SrcType::F32 && self.src_mod.is_none()
}
_ => false,
}
}

4
src/nouveau/compiler/nak_opt_copy_prop.rs
View File

@@ -313,9 +313,9 @@ impl CopyPropPass {
let dst = dst[0];
if !add.saturate {
if add.srcs[0].is_zero() {
if add.srcs[0].is_fneg_zero(SrcType::F32) {
self.add_copy(dst, SrcType::F32, add.srcs[1]);
} else if add.srcs[1].is_zero() {
} else if add.srcs[1].is_fneg_zero(SrcType::F32) {
self.add_copy(dst, SrcType::F32, add.srcs[0]);
}
}