diff --git a/src/Device/Blitter.cpp b/src/Device/Blitter.cpp
index 946eafc..611df31 100644
--- a/src/Device/Blitter.cpp
+++ b/src/Device/Blitter.cpp
@@ -1747,11 +1747,11 @@
 		return;
 	}
 
-	if((region.srcSubresource.layerCount != region.dstSubresource.layerCount) ||
-	   (region.srcSubresource.aspectMask != region.dstSubresource.aspectMask))
-	{
-		UNIMPLEMENTED("region");
-	}
+	// Vulkan 1.2 section 18.5. Image Copies with Scaling:
+	// "The layerCount member of srcSubresource and dstSubresource must match"
+	// "The aspectMask member of srcSubresource and dstSubresource must match"
+	ASSERT(region.srcSubresource.layerCount == region.dstSubresource.layerCount);
+	ASSERT(region.srcSubresource.aspectMask == region.dstSubresource.aspectMask);
 
 	if(region.dstOffsets[0].x > region.dstOffsets[1].x)
 	{
@@ -1890,10 +1890,9 @@
 	ASSERT(state.sourceFormat == state.destFormat);
 	ASSERT(state.srcSamples == state.destSamples);
 
-	if(state.srcSamples != 1)
-	{
-		UNIMPLEMENTED("state.srcSamples %d", state.srcSamples);
-	}
+	// Vulkan 1.2: "If samples is not VK_SAMPLE_COUNT_1_BIT, then imageType must be
+	// VK_IMAGE_TYPE_2D, flags must not contain VK_IMAGE_CREATE_CUBE_COMPATIBLE_BIT"
+	ASSERT(state.srcSamples == 1);
 
 	CornerUpdateFunction function;
 	{
@@ -1922,11 +1921,7 @@
 
 void Blitter::updateBorders(vk::Image *image, const VkImageSubresourceLayers &subresourceLayers)
 {
-	if(image->getArrayLayers() < (subresourceLayers.baseArrayLayer + 6))
-	{
-		UNIMPLEMENTED("image->getArrayLayers() %d, baseArrayLayer %d",
-		              image->getArrayLayers(), subresourceLayers.baseArrayLayer);
-	}
+	ASSERT(image->getArrayLayers() >= (subresourceLayers.baseArrayLayer + 6));
 
 	// From Vulkan 1.1 spec, section 11.5. Image Views:
 	// "For cube and cube array image views, the layers of the image view starting
@@ -1980,10 +1975,9 @@
 	VkSampleCountFlagBits samples = image->getSampleCountFlagBits();
 	State state(format, format, samples, samples, Options{ 0xF });
 
-	if(samples != VK_SAMPLE_COUNT_1_BIT)
-	{
-		UNIMPLEMENTED("Multi-sampled cube: %d samples", static_cast<int>(samples));
-	}
+	// Vulkan 1.2: "If samples is not VK_SAMPLE_COUNT_1_BIT, then imageType must be
+	// VK_IMAGE_TYPE_2D, flags must not contain VK_IMAGE_CREATE_CUBE_COMPATIBLE_BIT"
+	ASSERT(samples == VK_SAMPLE_COUNT_1_BIT);
 
 	auto cornerUpdateRoutine = getCornerUpdateRoutine(state);
 	if(!cornerUpdateRoutine)
diff --git a/src/Pipeline/SpirvShaderControlFlow.cpp b/src/Pipeline/SpirvShaderControlFlow.cpp
index f70a29c..6139002 100644
--- a/src/Pipeline/SpirvShaderControlFlow.cpp
+++ b/src/Pipeline/SpirvShaderControlFlow.cpp
@@ -581,13 +581,13 @@
 		{
 			if(insnNumber > 1)
 			{
-				UNIMPLEMENTED("Function block number of instructions: %d", insnNumber);
+				UNIMPLEMENTED("b/141246700: Function block number of instructions: %d", insnNumber);  // FIXME(b/141246700)
 				return EmitResult::Continue;
 			}
 
 			if(blockInsn.opcode() != wrapOpKill[insnNumber++])
 			{
-				UNIMPLEMENTED("Function block instruction %d : %s", insnNumber - 1, OpcodeName(blockInsn.opcode()).c_str());
+				UNIMPLEMENTED("b/141246700: Function block instruction %d : %s", insnNumber - 1, OpcodeName(blockInsn.opcode()).c_str());  // FIXME(b/141246700)
 				return EmitResult::Continue;
 			}
 
diff --git a/src/Pipeline/SpirvShaderMemory.cpp b/src/Pipeline/SpirvShaderMemory.cpp
index 8fcd939..c656216 100644
--- a/src/Pipeline/SpirvShaderMemory.cpp
+++ b/src/Pipeline/SpirvShaderMemory.cpp
@@ -225,7 +225,7 @@
 		Object::ID initializerId = insn.word(4);
 		if(getObject(initializerId).kind != Object::Kind::Constant)
 		{
-			UNIMPLEMENTED("Non-constant initializers not yet implemented");
+			UNIMPLEMENTED("b/148241854: Non-constant initializers not yet implemented");  // FIXME(b/148241854)
 		}
 
 		switch(objectTy.storageClass)
diff --git a/src/Vulkan/VkDebug.hpp b/src/Vulkan/VkDebug.hpp
index b0287f8..801a9ad 100644
--- a/src/Vulkan/VkDebug.hpp
+++ b/src/Vulkan/VkDebug.hpp
@@ -20,6 +20,8 @@
 #include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
+
+#include <cctype>
 #include <string>
 
 #if !defined(TRACE_OUTPUT_FILE)
@@ -110,11 +112,13 @@
 		}                                        \
 	} while(0)
 
-// A macro to indicate functionality currently unimplemented for a feature
-// advertised as supported. For unsupported features not advertised as supported
-// use UNSUPPORTED().
+// A macro to indicate functionality currently unimplemented, for a feature advertised
+// as supported. Since this is a bug, a bug ID must be provided, in b/### format.
+// For unimplemented functionality not advertised as supported, use UNSUPPORTED() instead.
 #undef UNIMPLEMENTED
-#define UNIMPLEMENTED(format, ...) DABORT("UNIMPLEMENTED: " format, ##__VA_ARGS__)
+#define UNIMPLEMENTED(format, ...)                   \
+	DABORT("UNIMPLEMENTED: " format, ##__VA_ARGS__); \
+	static_assert(format[0] == 'b' && format[1] == '/' && format[2] >= '0' && format[2] <= '9', "explanation must start with bug reference in b/### format")
 
 // A macro to indicate unsupported functionality.
 // This should be called when a Vulkan / SPIR-V feature is attempted to be used,
diff --git a/src/Vulkan/VkDeviceMemoryExternalAndroid.hpp b/src/Vulkan/VkDeviceMemoryExternalAndroid.hpp
index 6cd2c93..853d144 100644
--- a/src/Vulkan/VkDeviceMemoryExternalAndroid.hpp
+++ b/src/Vulkan/VkDeviceMemoryExternalAndroid.hpp
@@ -13,6 +13,8 @@
 // limitations under the License.
 
 #include "VkDebug.hpp"
+#include "VkStringify.hpp"
+
 #include <android/hardware_buffer.h>
 
 #include <errno.h>
@@ -55,7 +57,7 @@
 
 						if(exportInfo->handleTypes != VK_EXTERNAL_MEMORY_HANDLE_TYPE_ANDROID_HARDWARE_BUFFER_BIT_ANDROID)
 						{
-							UNIMPLEMENTED("exportInfo->handleTypes");
+							UNSUPPORTED("VkExportMemoryAllocateInfo::handleTypes %d", int(exportInfo->handleTypes));
 						}
 						exportAhb = true;
 					}
@@ -70,7 +72,8 @@
 					}
 					break;
 
-					default:;
+					default:
+						WARN("VkMemoryAllocateInfo->pNext sType = %s", vk::Stringify(createInfo->sType).c_str());
 				}
 				createInfo = createInfo->pNext;
 			}
@@ -146,7 +149,7 @@
 
 	static VkResult getAhbProperties(const struct AHardwareBuffer *buffer, VkAndroidHardwareBufferPropertiesANDROID *pProperties)
 	{
-		UNIMPLEMENTED("getAhbProperties");
+		UNIMPLEMENTED("b/141698760: getAhbProperties");  // FIXME(b/141698760)
 		return VK_SUCCESS;
 	}
 
diff --git a/src/Vulkan/VkDeviceMemoryExternalLinux.hpp b/src/Vulkan/VkDeviceMemoryExternalLinux.hpp
index 89dd4f9..3a9a768 100644
--- a/src/Vulkan/VkDeviceMemoryExternalLinux.hpp
+++ b/src/Vulkan/VkDeviceMemoryExternalLinux.hpp
@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include "VkDebug.hpp"
+#include "VkStringify.hpp"
 #include "System/Linux/MemFd.hpp"
 
 #include <errno.h>
@@ -47,7 +48,7 @@
 
 						if(importInfo->handleType != VK_EXTERNAL_MEMORY_HANDLE_TYPE_OPAQUE_FD_BIT)
 						{
-							UNIMPLEMENTED("importInfo->handleType");
+							UNSUPPORTED("VkImportMemoryFdInfoKHR::handleType %d", int(importInfo->handleType));
 						}
 						importFd = true;
 						fd = importInfo->fd;
@@ -59,13 +60,14 @@
 
 						if(exportInfo->handleTypes != VK_EXTERNAL_MEMORY_HANDLE_TYPE_OPAQUE_FD_BIT)
 						{
-							UNIMPLEMENTED("exportInfo->handleTypes");
+							UNSUPPORTED("VkExportMemoryAllocateInfo::handleTypes %d", int(exportInfo->handleTypes));
 						}
 						exportFd = true;
 					}
 					break;
 
-					default:;
+					default:
+						WARN("VkMemoryAllocateInfo->pNext sType = %s", vk::Stringify(createInfo->sType).c_str());
 				}
 				createInfo = createInfo->pNext;
 			}
diff --git a/src/Vulkan/VkImage.cpp b/src/Vulkan/VkImage.cpp
index 2a462ca..d538733 100644
--- a/src/Vulkan/VkImage.cpp
+++ b/src/Vulkan/VkImage.cpp
@@ -892,21 +892,15 @@
 
 void Image::clear(const VkClearColorValue &color, const VkImageSubresourceRange &subresourceRange)
 {
-	if(!(subresourceRange.aspectMask == VK_IMAGE_ASPECT_COLOR_BIT))
-	{
-		UNIMPLEMENTED("aspectMask");
-	}
+	ASSERT(subresourceRange.aspectMask == VK_IMAGE_ASPECT_COLOR_BIT);
 
 	device->getBlitter()->clear((void *)color.float32, getClearFormat(), this, format, subresourceRange);
 }
 
 void Image::clear(const VkClearDepthStencilValue &color, const VkImageSubresourceRange &subresourceRange)
 {
-	if((subresourceRange.aspectMask & ~(VK_IMAGE_ASPECT_DEPTH_BIT |
-	                                    VK_IMAGE_ASPECT_STENCIL_BIT)) != 0)
-	{
-		UNIMPLEMENTED("aspectMask");
-	}
+	ASSERT((subresourceRange.aspectMask & ~(VK_IMAGE_ASPECT_DEPTH_BIT |
+	                                        VK_IMAGE_ASPECT_STENCIL_BIT)) == 0);
 
 	if(subresourceRange.aspectMask & VK_IMAGE_ASPECT_DEPTH_BIT)
 	{
@@ -925,12 +919,9 @@
 
 void Image::clear(const VkClearValue &clearValue, const vk::Format &viewFormat, const VkRect2D &renderArea, const VkImageSubresourceRange &subresourceRange)
 {
-	if(!((subresourceRange.aspectMask == VK_IMAGE_ASPECT_COLOR_BIT) ||
-	     (subresourceRange.aspectMask & (VK_IMAGE_ASPECT_DEPTH_BIT |
-	                                     VK_IMAGE_ASPECT_STENCIL_BIT))))
-	{
-		UNIMPLEMENTED("subresourceRange");
-	}
+	ASSERT((subresourceRange.aspectMask == VK_IMAGE_ASPECT_COLOR_BIT) ||
+	       (subresourceRange.aspectMask & (VK_IMAGE_ASPECT_DEPTH_BIT |
+	                                       VK_IMAGE_ASPECT_STENCIL_BIT)));
 
 	if(subresourceRange.aspectMask == VK_IMAGE_ASPECT_COLOR_BIT)
 	{
diff --git a/src/Vulkan/VkImageView.cpp b/src/Vulkan/VkImageView.cpp
index 3142cfb..fc0c8bd 100644
--- a/src/Vulkan/VkImageView.cpp
+++ b/src/Vulkan/VkImageView.cpp
@@ -75,6 +75,7 @@
 {
 }
 
+// Vulkan 1.2 Table 8. Image and image view parameter compatibility requirements
 bool ImageView::imageTypesMatch(VkImageType imageType) const
 {
 	uint32_t imageArrayLayers = image->getArrayLayers();
@@ -118,15 +119,8 @@
 {
 	// Note: clearing ignores swizzling, so components is ignored.
 
-	if(!imageTypesMatch(image->getImageType()))
-	{
-		UNIMPLEMENTED("imageTypesMatch");
-	}
-
-	if(!format.isCompatible(image->getFormat()))
-	{
-		UNIMPLEMENTED("incompatible formats");
-	}
+	ASSERT(imageTypesMatch(image->getImageType()));
+	ASSERT(format.isCompatible(image->getFormat()));
 
 	VkImageSubresourceRange sr = subresourceRange;
 	sr.aspectMask = aspectMask;
@@ -137,15 +131,8 @@
 {
 	// Note: clearing ignores swizzling, so components is ignored.
 
-	if(!imageTypesMatch(image->getImageType()))
-	{
-		UNIMPLEMENTED("imageTypesMatch");
-	}
-
-	if(!format.isCompatible(image->getFormat()))
-	{
-		UNIMPLEMENTED("incompatible formats");
-	}
+	ASSERT(imageTypesMatch(image->getImageType()));
+	ASSERT(format.isCompatible(image->getFormat()));
 
 	VkImageSubresourceRange sr;
 	sr.aspectMask = aspectMask;
@@ -173,7 +160,7 @@
 {
 	if((subresourceRange.levelCount != 1) || (resolveAttachment->subresourceRange.levelCount != 1))
 	{
-		UNIMPLEMENTED("levelCount");
+		UNIMPLEMENTED("b/148242443: levelCount != 1");  // FIXME(b/148242443)
 	}
 
 	VkImageCopy region;
@@ -201,7 +188,7 @@
 {
 	if((subresourceRange.levelCount != 1) || (resolveAttachment->subresourceRange.levelCount != 1))
 	{
-		UNIMPLEMENTED("levelCount");
+		UNIMPLEMENTED("b/148242443: levelCount != 1");  // FIXME(b/148242443)
 	}
 
 	VkImageCopy region;
diff --git a/src/Vulkan/VkQueryPool.cpp b/src/Vulkan/VkQueryPool.cpp
index 07b29d7..30000f7 100644
--- a/src/Vulkan/VkQueryPool.cpp
+++ b/src/Vulkan/VkQueryPool.cpp
@@ -189,7 +189,7 @@
 
 	if(flags != 0)
 	{
-		UNIMPLEMENTED("vkCmdBeginQuery::flags %d", int(flags));
+		UNSUPPORTED("vkCmdBeginQuery::flags %d", int(flags));
 	}
 
 	pool[query].prepare(type);
diff --git a/src/Vulkan/VkSemaphore.cpp b/src/Vulkan/VkSemaphore.cpp
index 31eb5fd..72bee8b 100644
--- a/src/Vulkan/VkSemaphore.cpp
+++ b/src/Vulkan/VkSemaphore.cpp
@@ -15,6 +15,7 @@
 #include "VkSemaphore.hpp"
 
 #include "VkConfig.h"
+#include "VkStringify.hpp"
 
 #if SWIFTSHADER_EXTERNAL_SEMAPHORE_OPAQUE_FD
 #	if defined(__linux__) || defined(__ANDROID__)
@@ -50,15 +51,20 @@
 		for(const auto *nextInfo = reinterpret_cast<const VkBaseInStructure *>(pCreateInfo->pNext);
 		    nextInfo != nullptr; nextInfo = nextInfo->pNext)
 		{
-			if(nextInfo->sType == VK_STRUCTURE_TYPE_EXPORT_SEMAPHORE_CREATE_INFO)
+			switch(nextInfo->sType)
 			{
-				const auto *exportInfo = reinterpret_cast<const VkExportSemaphoreCreateInfo *>(nextInfo);
-				exportSemaphore = true;
-				if(exportInfo->handleTypes != Semaphore::External::kExternalSemaphoreHandleType)
+				case VK_STRUCTURE_TYPE_EXPORT_SEMAPHORE_CREATE_INFO:
 				{
-					UNIMPLEMENTED("exportInfo->handleTypes");
+					const auto *exportInfo = reinterpret_cast<const VkExportSemaphoreCreateInfo *>(nextInfo);
+					exportSemaphore = true;
+					if(exportInfo->handleTypes != Semaphore::External::kExternalSemaphoreHandleType)
+					{
+						UNSUPPORTED("exportInfo->handleTypes %d", int(exportInfo->handleTypes));
+					}
 				}
 				break;
+				default:
+					WARN("nextInfo->sType = %s", vk::Stringify(nextInfo->sType).c_str());
 			}
 		}
 	}
diff --git a/src/Vulkan/libVulkan.cpp b/src/Vulkan/libVulkan.cpp
index 6478702..f2146b1 100644
--- a/src/Vulkan/libVulkan.cpp
+++ b/src/Vulkan/libVulkan.cpp
@@ -273,7 +273,7 @@
 
 	if(pCreateInfo->enabledLayerCount != 0)
 	{
-		UNIMPLEMENTED("pCreateInfo->enabledLayerCount != 0");
+		UNIMPLEMENTED("b/148240133: pCreateInfo->enabledLayerCount != 0");  // FIXME(b/148240133)
 	}
 
 	uint32_t extensionPropertiesCount = sizeof(instanceExtensionProperties) / sizeof(instanceExtensionProperties[0]);