Report the maximum buffer offset alignment requirement

The buffer usage flags can contain multiple bits, so we must use the
maximum of the required offset alignments. While they're all 256
currently, this refactoring ensures the logic remains correct if we
modify them or handle other usage bits.

Bug: b/238916823
Change-Id: I189c8e25edae48266925c2ae1a70bfb13081bead
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/67088
Reviewed-by: Sean Risser <srisser@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>

src/Vulkan/VkBuffer.cpp

diff --git a/src/Vulkan/VkBuffer.cpp b/src/Vulkan/VkBuffer.cpp
index daa37d9..7912c52 100644
--- a/src/Vulkan/VkBuffer.cpp
+++ b/src/Vulkan/VkBuffer.cpp
@@ -17,6 +17,7 @@
 #include "VkConfig.hpp"
 #include "VkDeviceMemory.hpp"
 
+#include <algorithm>
 #include <cstring>
 #include <limits>
 
@@ -66,22 +67,21 @@
 	VkMemoryRequirements memoryRequirements = {};
 
 	memoryRequirements.size = size;
+	memoryRequirements.alignment = REQUIRED_MEMORY_ALIGNMENT;
 
 	if(usage & (VK_BUFFER_USAGE_STORAGE_TEXEL_BUFFER_BIT | VK_BUFFER_USAGE_UNIFORM_TEXEL_BUFFER_BIT))
 	{
-		memoryRequirements.alignment = vk::MIN_TEXEL_BUFFER_OFFSET_ALIGNMENT;
+		memoryRequirements.alignment = std::max(memoryRequirements.alignment, vk::MIN_TEXEL_BUFFER_OFFSET_ALIGNMENT);
 	}
-	else if(usage & VK_BUFFER_USAGE_STORAGE_BUFFER_BIT)
+
+	if(usage & VK_BUFFER_USAGE_STORAGE_BUFFER_BIT)
 	{
-		memoryRequirements.alignment = vk::MIN_STORAGE_BUFFER_OFFSET_ALIGNMENT;
+		memoryRequirements.alignment = std::max(memoryRequirements.alignment, vk::MIN_STORAGE_BUFFER_OFFSET_ALIGNMENT);
 	}
-	else if(usage & VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT)
+
+	if(usage & VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT)
 	{
-		memoryRequirements.alignment = vk::MIN_UNIFORM_BUFFER_OFFSET_ALIGNMENT;
-	}
-	else
-	{
-		memoryRequirements.alignment = REQUIRED_MEMORY_ALIGNMENT;
+		memoryRequirements.alignment = std::max(memoryRequirements.alignment, vk::MIN_UNIFORM_BUFFER_OFFSET_ALIGNMENT);
 	}
 
 	memoryRequirements.memoryTypeBits = vk::MEMORY_TYPE_GENERIC_BIT;