Fix signed/unsigned comparison warnings.

Bug 15387371

Change-Id: Id4c9b54c5c0b4115479b6710c4d8c91d34e5c002
Reviewed-on: https://swiftshader-review.googlesource.com/4494
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
diff --git a/src/Shader/VertexProgram.cpp b/src/Shader/VertexProgram.cpp
index 40c0910..e4587cc 100644
--- a/src/Shader/VertexProgram.cpp
+++ b/src/Shader/VertexProgram.cpp
@@ -646,11 +646,10 @@
 		}
 	}
 
-	Vector4f VertexProgram::fetchRegisterF(Registers &r, const Src &src, int offset)
+	Vector4f VertexProgram::fetchRegisterF(Registers &r, const Src &src, unsigned int offset)
 	{
-		int i = src.index + offset;
-
 		Vector4f reg;
+		unsigned int i = src.index + offset;
 
 		switch(src.type)
 		{
@@ -762,11 +761,10 @@
 		return mod;
 	}
 
-	Vector4f VertexProgram::readConstant(Registers &r, const Src &src, int offset)
+	Vector4f VertexProgram::readConstant(Registers &r, const Src &src, unsigned int offset)
 	{
 		Vector4f c;
-
-		int i = src.index + offset;
+		unsigned int i = src.index + offset;
 
 		if(src.rel.type == Shader::PARAMETER_VOID)   // Not relative
 		{