From: Chris Forbes <chrisforbes@google.com>
Date: Wed, 20 Mar 2019 21:50:24 +0000 (-0700)
Subject: Add support for derivative instructions
X-Git-Tag: android-x86-9.0-r1~109
X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=aff2dd06;p=android-x86%2Fexternal-swiftshader.git

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 f348c03cc..212a0ae2a 100644
--- a/src/Pipeline/SpirvShader.cpp
+++ b/src/Pipeline/SpirvShader.cpp
@@ -401,6 +401,15 @@ namespace sw
 			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 @@ namespace sw
 		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 @@ namespace sw
 			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());
 			}