Revert "SprivShader: Replace hand-rolled bitcount with LLVM intrinsic"

src/Pipeline/SpirvShader.cpp

@@ -2771,11 +2771,25 @@ namespace sw
 				break;
 			}
 			case spv::OpBitReverse:
+			{
 				dst.move(i, BitReverse(src.UInt(i)));
 				break;
+			}
 			case spv::OpBitCount:
-				dst.move(i, BitCount(src.UInt(i)));
+			{
+				// TODO: Add an intrinsic to reactor. Even if there isn't a
+				// single vector instruction, there may be target-dependent
+				// ways to make this faster.
+				// https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
+				auto v = src.UInt(i);
+				SIMD::UInt c = v - ((v >> 1) & SIMD::UInt(0x55555555));
+				c = ((c >> 2) & SIMD::UInt(0x33333333)) + (c & SIMD::UInt(0x33333333));
+				c = ((c >> 4) + c) & SIMD::UInt(0x0F0F0F0F);
+				c = ((c >> 8) + c) & SIMD::UInt(0x00FF00FF);
+				c = ((c >> 16) + c) & SIMD::UInt(0x0000FFFF);
+				dst.move(i, c);
 				break;
+			}
 			case spv::OpSNegate:
 				dst.move(i, -src.Int(i));
 				break;

src/Reactor/LLVMReactor.cpp

@@ -3220,12 +3220,6 @@ namespace rr
 		return RValue<UInt4>(V(::builder->CreateCall(func, { V(v.value) })));
 	}
 
-	RValue<UInt4> BitCount(RValue<UInt4> v)
-	{
-		auto func = llvm::Intrinsic::getDeclaration(::module, llvm::Intrinsic::ctpop, { T(UInt4::getType()) } );
-		return RValue<UInt4>(V(::builder->CreateCall(func, { V(v.value) })));
-	}
-
 	RValue<UInt4> Ctlz(RValue<UInt4> v, bool isZeroUndef)
 	{
 #if REACTOR_LLVM_VERSION < 7

src/Reactor/Reactor.hpp

@@ -2233,7 +2233,6 @@ namespace rr
 	// Bit Manipulation functions.
 	// TODO: Currentlhy unimplemented for Subzero.
 	RValue<UInt4> BitReverse(RValue<UInt4> x);
-	RValue<UInt4> BitCount(RValue<UInt4> x);
 
 	// Count leading zeros.
 	// Returns 32 when: isZeroUndef && x == 0.

src/Reactor/SubzeroReactor.cpp

@@ -3371,17 +3371,6 @@ namespace rr
 		return v;
 	}
 
-	RValue<UInt4> BitCount(RValue<UInt4> x)
-	{
-		// https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
-		UInt4 v = x - ((x >> 1) & UInt4(0x55555555));
-		v = ((v >> 2) & UInt4(0x33333333)) + (v & UInt4(0x33333333));
-		v = ((v >> 4) + v) & UInt4(0x0F0F0F0F);
-		v = ((v >> 8) + v) & UInt4(0x00FF00FF);
-		v = ((v >> 16) + v) & UInt4(0x0000FFFF);
-		return v;
-	}
-
 	Type *Float4::getType()
 	{
 		return T(Ice::IceType_v4f32);