Fix duplicated initialization for loop variables with initializers.

reference/shaders-no-opt/asm/comp/loop-variable-with-initializer.asm.comp

@@ -0,0 +1,12 @@
+#version 450
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+
+void main()
+{
+    uint i = 0u;
+    for (;;)
+    {
+        break;
+    }
+}
+

shaders-no-opt/asm/comp/loop-variable-with-initializer.asm.comp

@@ -0,0 +1,31 @@
+; SPIR-V
+; Version: 1.3
+; Generator: Khronos; 0
+; Bound: 62
+; Schema: 0
+               OpCapability Shader
+			   OpMemoryModel Logical GLSL450
+               OpEntryPoint GLCompute %main "main"
+			   OpExecutionMode %main LocalSize 1 1 1
+               OpName %main "main"
+               OpName %i "i"
+       %uint = OpTypeInt 32 0
+       %void = OpTypeVoid
+         %11 = OpTypeFunction %void
+      %uint_0 = OpConstant %uint 0
+%_ptr_Function_uint = OpTypePointer Function %uint
+         %31 = OpConstantNull %uint
+       %main = OpFunction %void None %11
+         %14 = OpLabel
+          %i = OpVariable %_ptr_Function_uint Function %31
+               OpStore %i %uint_0
+               OpBranch %32
+         %32 = OpLabel
+               OpLoopMerge %33 %34 None
+               OpBranch %33
+         %34 = OpLabel
+         %57 = OpLoad %uint %i
+               OpBranch %32
+         %33 = OpLabel
+               OpReturn
+               OpFunctionEnd

spirv_glsl.cpp

@@ -12311,7 +12311,8 @@ void CompilerGLSL::emit_function(SPIRFunction &func, const Bitset &return_flags)
 		{
 			add_local_variable_name(var.self);
 
-			if (var.initializer)
+			// Loop variables should never be declared early, they are explicitly emitted in a loop.
+			if (var.initializer && !var.loop_variable)
 				statement(variable_decl_function_local(var), ";");
 			else
 			{