Fix specialization constant patching on D3D12.

Author: blueskythlikesclouds

drivers/d3d12/rendering_shader_container_d3d12.cpp

@@ -94,28 +94,26 @@ uint32_t RenderingDXIL::patch_specialization_constant(
 		const uint64_t (&p_stages_bit_offsets)[D3D12_BITCODE_OFFSETS_NUM_STAGES],
 		HashMap<RenderingDeviceCommons::ShaderStage, Vector<uint8_t>> &r_stages_bytecodes,
 		bool p_is_first_patch) {
-	uint32_t patch_val = 0;
+	int64_t patch_val = 0;
 	switch (p_type) {
 		case RenderingDeviceCommons::PIPELINE_SPECIALIZATION_CONSTANT_TYPE_INT: {
-			uint32_t int_value = *((const int *)p_value);
-			ERR_FAIL_COND_V(int_value & (1 << 31), 0);
-			patch_val = int_value;
+			patch_val = *((const int32_t *)p_value);
 		} break;
 		case RenderingDeviceCommons::PIPELINE_SPECIALIZATION_CONSTANT_TYPE_BOOL: {
 			bool bool_value = *((const bool *)p_value);
-			patch_val = (uint32_t)bool_value;
+			patch_val = (int32_t)bool_value;
 		} break;
 		case RenderingDeviceCommons::PIPELINE_SPECIALIZATION_CONSTANT_TYPE_FLOAT: {
-			uint32_t int_value = *((const int *)p_value);
-			ERR_FAIL_COND_V(int_value & (1 << 31), 0);
-			patch_val = (int_value >> 1);
+			patch_val = *((const int32_t *)p_value);
 		} break;
 	}
-	// For VBR encoding to encode the number of bits we expect (32), we need to set the MSB unconditionally.
-	// However, signed VBR moves the MSB to the LSB, so setting the MSB to 1 wouldn't help. Therefore,
-	// the bit we set to 1 is the one at index 30.
-	patch_val |= (1 << 30);
-	patch_val <<= 1; // What signed VBR does.
+
+	// Encode to signed VBR.
+	if (patch_val >= 0) {
+		patch_val <<= 1;
+	} else {
+		patch_val = ((-patch_val) << 1) | 1;
+	}
 
 	auto tamper_bits = [](uint8_t *p_start, uint64_t p_bit_offset, uint64_t p_tb_value) -> uint64_t {
 		uint64_t original = 0;
@@ -169,13 +167,13 @@ uint32_t RenderingDXIL::patch_specialization_constant(
 
 		Vector<uint8_t> &bytecode = r_stages_bytecodes[(RenderingDeviceCommons::ShaderStage)stage];
 #ifdef DEV_ENABLED
-		uint64_t orig_patch_val = tamper_bits(bytecode.ptrw(), offset, patch_val);
+		uint64_t orig_patch_val = tamper_bits(bytecode.ptrw(), offset, (uint64_t)patch_val);
 		// Checking against the value the NIR patch should have set.
 		DEV_ASSERT(!p_is_first_patch || ((orig_patch_val >> 1) & GODOT_NIR_SC_SENTINEL_MAGIC_MASK) == GODOT_NIR_SC_SENTINEL_MAGIC);
-		uint64_t readback_patch_val = tamper_bits(bytecode.ptrw(), offset, patch_val);
-		DEV_ASSERT(readback_patch_val == patch_val);
+		uint64_t readback_patch_val = tamper_bits(bytecode.ptrw(), offset, (uint64_t)patch_val);
+		DEV_ASSERT(readback_patch_val == (uint64_t)patch_val);
 #else
-		tamper_bits(bytecode.ptrw(), offset, patch_val);
+		tamper_bits(bytecode.ptrw(), offset, (uint64_t)patch_val);
 #endif
 
 		stages_patched_mask |= (1 << stage);