Add support for derivative instructions
- OpDPdx
- OpDPdy
- OpFwidth
- OpDPdxCoarse
- OpDPdyCoarse
- OpFwidthCoarse
- OpDPdxFine
- OpDPdyFine
- OpFwidthFine
We have flexibility in how we implement the OpDPdx, OpDPdy and OpFwidth
instructions; they can return either coarse or fine derivatives.
I have chosen to make them equivalent to the coarse derivatives since
those are slightly cheaper to compute.
Added a static assert to ensure we revisit these when considering other
vector widths.
Bug: b/129002115
Test: dEQP-VK.glsl.derivate.*
Change-Id: I75224c1e77c1eefac4f219be5662836daa86a098
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/27689
Tested-by: Chris Forbes <chrisforbes@google.com>
Presubmit-Ready: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
diff --git a/src/Pipeline/SpirvShader.cpp b/src/Pipeline/SpirvShader.cpp
index f348c03..212a0ae 100644
--- a/src/Pipeline/SpirvShader.cpp
+++ b/src/Pipeline/SpirvShader.cpp
@@ -401,6 +401,15 @@
case spv::OpIsNan:
case spv::OpAny:
case spv::OpAll:
+ case spv::OpDPdx:
+ case spv::OpDPdxCoarse:
+ case spv::OpDPdy:
+ case spv::OpDPdyCoarse:
+ case spv::OpFwidth:
+ case spv::OpFwidthCoarse:
+ case spv::OpDPdxFine:
+ case spv::OpDPdyFine:
+ case spv::OpFwidthFine:
// Instructions that yield an intermediate value
{
Type::ID typeId = insn.word(1);
@@ -1229,6 +1238,15 @@
case spv::OpBitcast:
case spv::OpIsInf:
case spv::OpIsNan:
+ case spv::OpDPdx:
+ case spv::OpDPdxCoarse:
+ case spv::OpDPdy:
+ case spv::OpDPdyCoarse:
+ case spv::OpFwidth:
+ case spv::OpFwidthCoarse:
+ case spv::OpDPdxFine:
+ case spv::OpDPdyFine:
+ case spv::OpFwidthFine:
EmitUnaryOp(insn, routine);
break;
@@ -1764,6 +1782,58 @@
case spv::OpIsNan:
dst.emplace(i, IsNan(src.Float(i)));
break;
+ case spv::OpDPdx:
+ case spv::OpDPdxCoarse:
+ // Derivative instructions: FS invocations are laid out like so:
+ // 0 1
+ // 2 3
+ static_assert(SIMD::Width == 4, "All cross-lane instructions will need care when using a different width");
+ dst.emplace(i, SIMD::Float(Extract(src.Float(i), 1) - Extract(src.Float(i), 0)));
+ break;
+ case spv::OpDPdy:
+ case spv::OpDPdyCoarse:
+ dst.emplace(i, SIMD::Float(Extract(src.Float(i), 2) - Extract(src.Float(i), 0)));
+ break;
+ case spv::OpFwidth:
+ case spv::OpFwidthCoarse:
+ dst.emplace(i, SIMD::Float(Abs(Extract(src.Float(i), 1) - Extract(src.Float(i), 0))
+ + Abs(Extract(src.Float(i), 2) - Extract(src.Float(i), 0))));
+ break;
+ case spv::OpDPdxFine:
+ {
+ auto firstRow = Extract(src.Float(i), 1) - Extract(src.Float(i), 0);
+ auto secondRow = Extract(src.Float(i), 3) - Extract(src.Float(i), 2);
+ SIMD::Float v = SIMD::Float(firstRow);
+ v = Insert(v, secondRow, 2);
+ v = Insert(v, secondRow, 3);
+ dst.emplace(i, v);
+ break;
+ }
+ case spv::OpDPdyFine:
+ {
+ auto firstColumn = Extract(src.Float(i), 2) - Extract(src.Float(i), 0);
+ auto secondColumn = Extract(src.Float(i), 3) - Extract(src.Float(i), 1);
+ SIMD::Float v = SIMD::Float(firstColumn);
+ v = Insert(v, secondColumn, 1);
+ v = Insert(v, secondColumn, 3);
+ dst.emplace(i, v);
+ break;
+ }
+ case spv::OpFwidthFine:
+ {
+ auto firstRow = Extract(src.Float(i), 1) - Extract(src.Float(i), 0);
+ auto secondRow = Extract(src.Float(i), 3) - Extract(src.Float(i), 2);
+ SIMD::Float dpdx = SIMD::Float(firstRow);
+ dpdx = Insert(dpdx, secondRow, 2);
+ dpdx = Insert(dpdx, secondRow, 3);
+ auto firstColumn = Extract(src.Float(i), 2) - Extract(src.Float(i), 0);
+ auto secondColumn = Extract(src.Float(i), 3) - Extract(src.Float(i), 1);
+ SIMD::Float dpdy = SIMD::Float(firstColumn);
+ dpdy = Insert(dpdy, secondColumn, 1);
+ dpdy = Insert(dpdy, secondColumn, 3);
+ dst.emplace(i, Abs(dpdx) + Abs(dpdy));
+ break;
+ }
default:
UNIMPLEMENTED("Unhandled unary operator %s", OpcodeName(insn.opcode()).c_str());
}
