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

src/Pipeline/SpirvShader.cpp

@@ -2772,7 +2772,17 @@ namespace sw
 			}
 			case spv::OpBitReverse:
 			{
-				dst.move(i, BitReverse(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#ReverseParallel
+				SIMD::UInt v = src.UInt(i);
+				v = ((v >> 1) & SIMD::UInt(0x55555555)) | ((v & SIMD::UInt(0x55555555)) << 1);
+				v = ((v >> 2) & SIMD::UInt(0x33333333)) | ((v & SIMD::UInt(0x33333333)) << 2);
+				v = ((v >> 4) & SIMD::UInt(0x0F0F0F0F)) | ((v & SIMD::UInt(0x0F0F0F0F)) << 4);
+				v = ((v >> 8) & SIMD::UInt(0x00FF00FF)) | ((v & SIMD::UInt(0x00FF00FF)) << 8);
+				v = (v >> 16) | (v << 16);
+				dst.move(i, v);
 				break;
 			}
 			case spv::OpBitCount:

src/Reactor/LLVMReactor.cpp

@@ -3214,12 +3214,6 @@ namespace rr
 		return RValue<Float4>(V(::builder->CreateCall(func, V(v.value))));
 	}
 
-	RValue<UInt4> BitReverse(RValue<UInt4> v)
-	{
-		auto func = llvm::Intrinsic::getDeclaration(::module, llvm::Intrinsic::bitreverse, { 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

@@ -2232,7 +2232,6 @@ namespace rr
 
 	// Bit Manipulation functions.
 	// TODO: Currentlhy unimplemented for Subzero.
-	RValue<UInt4> BitReverse(RValue<UInt4> x);
 
 	// Count leading zeros.
 	// Returns 32 when: isZeroUndef && x == 0.

src/Reactor/SubzeroReactor.cpp

@@ -3359,18 +3359,6 @@ namespace rr
 		}
 	}
 
-	RValue<UInt4> BitReverse(RValue<UInt4> x)
-	{
-		// https://graphics.stanford.edu/~seander/bithacks.html#ReverseParallel
-		UInt4 v = x;
-		v = ((v >> 1) & UInt4(0x55555555)) | ((v & UInt4(0x55555555)) << 1);
-		v = ((v >> 2) & UInt4(0x33333333)) | ((v & UInt4(0x33333333)) << 2);
-		v = ((v >> 4) & UInt4(0x0F0F0F0F)) | ((v & UInt4(0x0F0F0F0F)) << 4);
-		v = ((v >> 8) & UInt4(0x00FF00FF)) | ((v & UInt4(0x00FF00FF)) << 8);
-		v = (v >> 16) | (v << 16);
-		return v;
-	}
-
 	Type *Float4::getType()
 	{
 		return T(Ice::IceType_v4f32);